Spring依赖注入

时间：2024-10-30 10:24:03

一、什么是依赖注入

DI (Dependency Injection)：依赖注入是指在 Spring IOC 容器创建对象的过程中，将所依赖的对象通过配置进行注入。我们可以通过依赖注入的方式来降低对象间的耦合度。

在软件工程中，对象之间的耦合度就是对象之间的依赖性。对象之间的耦合越高，维护成本越高，因此对象的设计应使对象之间的耦合越小越好。

1 类的关系

继承、实现、依赖、关联、聚合、组合。

2 关系强度

继承 = 实现 > 组合 > 聚合 > 关联 > 依赖

二、为什么使用依赖注入

1 开闭原则

1.1 定义

OCP (Open Close Principle)： 软件本身应该是可扩展的，而不可修改的。也就是，对扩展开放，对修改封闭的。

1.2 开闭原则优点

易扩展。开闭原则的定义就要求对扩展开放。

易维护。软件开发中，对现有代码的修改是一件很有风险的事情，符合开闭原则的设计在扩展时无需修改现有代码，规避了这个风险，大大提交了可维护性。

2 高内聚，低耦合

高内聚是指相关度比较高的部分尽可能的集中，不要分散。

低耦合就是说两个相关的模块尽可以能把依赖的部分降低到最小，不要产生强依赖。

三、依赖注入的方式

在使用依赖注入时，如果注入的是 Bean 对象，那么要求注入的 Bean 对象与被注入的Bean 对象都需要 Spring IOC 容器来实例化。

1 通过 Set 方法注入

需要为注入的成员变量提供 Set 方法。

1.1 POJO中添加属性、set方法和toString方法

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">class</span> <span style="color:#0000ff">GirlfriendOYY</span> <span style="color:#770088">implements</span> <span style="color:#000000">Girlfriend</span> {
    

    2. 

  2. 

    

        <span style="color:#770088">private</span> <span style="color:#008855">double</span> <span style="color:#000000">hight</span>;
    

    3. 

  3. 

    

        <span style="color:#770088">private</span> <span style="color:#008855">String</span> <span style="color:#000000">education</span>;
    

    4. 

  4. 

    

    ​
    

    5. 

  5. 

    

        <span style="color:#555555">@Override</span>
    

    6. 

  6. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">String</span> <span style="color:#000000">toString</span>() {
    

    7. 

  7. 

    

            <span style="color:#770088">return</span> <span style="color:#aa1111">"GirlfriendOYY{"</span> <span style="color:#981a1a">+</span>
    

    8. 

  8. 

    

                    <span style="color:#aa1111">"hight="</span> <span style="color:#981a1a">+</span> <span style="color:#000000">hight</span> <span style="color:#981a1a">+</span>
    

    9. 

  9. 

    

                    <span style="color:#aa1111">", education='"</span> <span style="color:#981a1a">+</span> <span style="color:#000000">education</span> <span style="color:#981a1a">+</span> <span style="color:#aa1111">'\''</span> <span style="color:#981a1a">+</span>
    

    10. 

  10. 

    

                    <span style="color:#aa1111">'}'</span>;
    

    11. 

  11. 

    

        }
    

    12. 

  12. 

    

    ​
    

    13. 

  13. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">double</span> <span style="color:#000000">getHight</span>() {
    

    14. 

  14. 

    

            <span style="color:#770088">return</span> <span style="color:#000000">hight</span>;
    

    15. 

  15. 

    

        }
    

    16. 

  16. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">void</span> <span style="color:#000000">setHight</span>(<span style="color:#008855">double</span> <span style="color:#000000">hight</span>) {
    

    17. 

  17. 

    

            <span style="color:#770088">this</span>.<span style="color:#000000">hight</span> <span style="color:#981a1a">=</span> <span style="color:#000000">hight</span>;
    

    18. 

  18. 

    

        }
    

    19. 

  19. 

    

    ​
    

    20. 

  20. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">String</span> <span style="color:#000000">getEducation</span>() {
    

    21. 

  21. 

    

            <span style="color:#770088">return</span> <span style="color:#000000">education</span>;
    

    22. 

  22. 

    

        }
    

    23. 

  23. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">void</span> <span style="color:#000000">setEducation</span>(<span style="color:#008855">String</span> <span style="color:#000000">education</span>) {
    

    24. 

  24. 

    

            <span style="color:#770088">this</span>.<span style="color:#000000">education</span> <span style="color:#981a1a">=</span> <span style="color:#000000">education</span>;
    

    25. 

  25. 

    

        }
    

    26. 

  26. 

    

    }</span></span>
    

    27.

1.2 Spring的xml配置文件

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333">    <span style="color:#aa5500"><!--1.1 通过构造方法创建对象--></span>
    

    2. 

  2. 

    

        <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gf1"</span> <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span>
    

    3. 

  3. 

    

              <span style="color:#0000cc">scope</span>=<span style="color:#aa1111">"prototype"</span> <span style="color:#0000cc">lazy-init</span>=<span style="color:#aa1111">"false"</span><span style="color:#117700">></span>
    

    4. 

  4. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"education"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"本科"</span> <span style="color:#117700">/></span>
    

    5. 

  5. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"hight"</span> <span style="color:#117700">></span>
    

    6. 

  6. 

    

                <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>1.65<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    7. 

  7. 

    

            <span style="color:#117700"></</span><span style="color:#117700">property</span><span style="color:#117700">></span>
    

    8. 

  8. 

    

        <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span></span></span>
    

    9.

1.3 测试

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">class</span> <span style="color:#0000ff">TestGirlfriend</span> {
    

    2. 

  2. 

    

        <span style="color:#770088">public</span> <span style="color:#770088">static</span> <span style="color:#008855">void</span> <span style="color:#000000">main</span>(<span style="color:#008855">String</span>[] <span style="color:#000000">args</span>) {
    

    3. 

  3. 

    

            <span style="color:#000000">ApplicationContext</span> <span style="color:#000000">ac</span> <span style="color:#981a1a">=</span> <span style="color:#770088">new</span> <span style="color:#000000">ClassPathXmlApplicationContext</span>(<span style="color:#aa1111">"application_context.xml"</span>);
    

    4. 

  4. 

    

            <span style="color:#000000">Girlfriend</span> <span style="color:#000000">gf</span> <span style="color:#981a1a">=</span> (<span style="color:#000000">Girlfriend</span>) <span style="color:#000000">ac</span>.<span style="color:#000000">getBean</span>(<span style="color:#aa1111">"gf1"</span>);
    

    5. 

  5. 

    

            <span style="color:#000000">System</span>.<span style="color:#000000">out</span>.<span style="color:#000000">println</span>(<span style="color:#000000">gf</span>);
    

    6. 

  6. 

    

        }
    

    7. 

  7. 

    

    }</span></span>
    

    8.

运行结果

2 通过构造方法注入

Bean 对象中需要提供有参的构造方法

name:根据参数名称识别参数

index:根据参数的位置来识别参数

type:根据参数的类型识别参数

2.1 POJO中添加有参构造方法

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">class</span> <span style="color:#0000ff">GirlfriendOYY</span> <span style="color:#770088">implements</span> <span style="color:#000000">Girlfriend</span> {
    

    2. 

  2. 

    

        <span style="color:#770088">private</span> <span style="color:#008855">double</span> <span style="color:#000000">hight</span>;
    

    3. 

  3. 

    

        <span style="color:#770088">private</span> <span style="color:#008855">String</span> <span style="color:#000000">education</span>;
    

    4. 

  4. 

    

    ​
    

    5. 

  5. 

    

        <span style="color:#770088">public</span> <span style="color:#000000">GirlfriendOYY</span>(<span style="color:#008855">double</span> <span style="color:#000000">hight</span>, <span style="color:#008855">String</span> <span style="color:#000000">education</span>) {
    

    6. 

  6. 

    

            <span style="color:#770088">this</span>.<span style="color:#000000">hight</span> <span style="color:#981a1a">=</span> <span style="color:#000000">hight</span>;
    

    7. 

  7. 

    

            <span style="color:#770088">this</span>.<span style="color:#000000">education</span> <span style="color:#981a1a">=</span> <span style="color:#000000">education</span>;
    

    8. 

  8. 

    

        }
    

    9. 

  9. 

    

    }</span></span>
    

    10.

2.2 Spring的xml配置文件

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333">    <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gf4"</span> <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span><span style="color:#117700">></span>
    

    2. 

  2. 

    

            <span style="color:#117700"><</span><span style="color:#117700">constructor-arg</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"education"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"专科"</span><span style="color:#117700">/></span>
    

    3. 

  3. 

    

            <span style="color:#117700"><</span><span style="color:#117700">constructor-arg</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"hight"</span> <span style="color:#117700">></span>
    

    4. 

  4. 

    

                <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>1.65<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    5. 

  5. 

    

            <span style="color:#117700"></</span><span style="color:#117700">constructor-arg</span><span style="color:#117700">></span>
    

    6. 

  6. 

    

        <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span>
    

    7. 

  7. 

    

        <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gf5"</span> <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span><span style="color:#117700">></span>
    

    8. 

  8. 

    

            <span style="color:#117700"><</span><span style="color:#117700">constructor-arg</span> <span style="color:#0000cc">index</span>=<span style="color:#aa1111">"0"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"1.68"</span> <span style="color:#117700">/></span>
    

    9. 

  9. 

    

            <span style="color:#117700"><</span><span style="color:#117700">constructor-arg</span> <span style="color:#0000cc">index</span>=<span style="color:#aa1111">"1"</span> <span style="color:#117700">></span>
    

    10. 

  10. 

    

                <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>高中<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    11. 

  11. 

    

            <span style="color:#117700"></</span><span style="color:#117700">constructor-arg</span><span style="color:#117700">></span>
    

    12. 

  12. 

    

        <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span>
    

    13. 

  13. 

    

        <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gf6"</span> <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span><span style="color:#117700">></span>
    

    14. 

  14. 

    

            <span style="color:#117700"><</span><span style="color:#117700">constructor-arg</span> <span style="color:#0000cc">type</span>=<span style="color:#aa1111">"double"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"1.73"</span> <span style="color:#117700">/></span>
    

    15. 

  15. 

    

            <span style="color:#117700"><</span><span style="color:#117700">constructor-arg</span> <span style="color:#0000cc">type</span>=<span style="color:#aa1111">""</span> <span style="color:#117700">></span>
    

    16. 

  16. 

    

                <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>硕士<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    17. 

  17. 

    

            <span style="color:#117700"></</span><span style="color:#117700">constructor-arg</span><span style="color:#117700">></span>
    

    18. 

  18. 

    

        <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span></span></span>
    

    19.

2.3 测试

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">class</span> <span style="color:#0000ff">TestGirlfriend</span> {
    

    2. 

  2. 

    

        <span style="color:#770088">public</span> <span style="color:#770088">static</span> <span style="color:#008855">void</span> <span style="color:#000000">main</span>(<span style="color:#008855">String</span>[] <span style="color:#000000">args</span>) {
    

    3. 

  3. 

    

            <span style="color:#000000">ApplicationContext</span> <span style="color:#000000">ac</span> <span style="color:#981a1a">=</span> <span style="color:#770088">new</span> <span style="color:#000000">ClassPathXmlApplicationContext</span>(<span style="color:#aa1111">"application_context.xml"</span>);
    

    4. 

  4. 

    

            <span style="color:#000000">Girlfriend</span> <span style="color:#000000">gf</span> <span style="color:#981a1a">=</span> (<span style="color:#000000">Girlfriend</span>) <span style="color:#000000">ac</span>.<span style="color:#000000">getBean</span>(<span style="color:#aa1111">"gf4"</span>);
    

    5. 

  5. 

    

            <span style="color:#000000">System</span>.<span style="color:#000000">out</span>.<span style="color:#000000">println</span>(<span style="color:#000000">gf</span>);
    

    6. 

  6. 

    

             <span style="color:#000000">gf</span> <span style="color:#981a1a">=</span> (<span style="color:#000000">Girlfriend</span>) <span style="color:#000000">ac</span>.<span style="color:#000000">getBean</span>(<span style="color:#aa1111">"gf5"</span>);
    

    7. 

  7. 

    

            <span style="color:#000000">System</span>.<span style="color:#000000">out</span>.<span style="color:#000000">println</span>(<span style="color:#000000">gf</span>);
    

    8. 

  8. 

    

             <span style="color:#000000">gf</span> <span style="color:#981a1a">=</span> (<span style="color:#000000">Girlfriend</span>) <span style="color:#000000">ac</span>.<span style="color:#000000">getBean</span>(<span style="color:#aa1111">"gf6"</span>);
    

    9. 

  9. 

    

            <span style="color:#000000">System</span>.<span style="color:#000000">out</span>.<span style="color:#000000">println</span>(<span style="color:#000000">gf</span>);
    

    10. 

  10. 

    

        }
    

    11. 

  11. 

    

    }</span></span>
    

    12.

运行结果：

3 自动注入

自动注入的方式有两种，一种是全局配置自动注入，另一种是局部配置自动注入。

无论全局配置或局部单独配置，都有 5 个值可以选择：

no：当 autowire 设置为 no 的时候，Spring 就不会进行自动注入。

byName：在 Spring 容器中查找 id 与属性名相同的 bean，并进行注入。需要提供 set 方法。

byType：在 Spring 容器中查找类型与属性名的类型相同的 bean，并进行注入。需要提供 set 方法。

constructor：仍旧是使用 byName 方式，只不过注入的时候，使用构造方式进行注入。

default：全局配置的 default 相当于 no，局部的 default 表示使用全局配置设置。

3.1 局部自动注入

通过 bean 标签中的 autowire 属性配置自动注入。

有效范围：仅针对当前 bean 标签生效。

3.1.1 POJO

接口：

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">interface</span> <span style="color:#0000ff">GirlfriendProxyService</span> {
    

    2. 

  2. 

    

        <span style="color:#000000">Girlfriend</span> <span style="color:#000000">findGirlFriend</span>();
    

    3. 

  3. 

    

    }</span></span>
    

    4.

实现类：

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">class</span> <span style="color:#0000ff">GirlfriendProxyServiceImpl</span> <span style="color:#770088">implements</span> <span style="color:#000000">GirlfriendProxyService</span> {
    

    2. 

  2. 

    

        <span style="color:#000000">Girlfriend</span> <span style="color:#000000">girlfriend</span>;
    

    3. 

  3. 

    

        <span style="color:#770088">public</span> <span style="color:#000000">GirlfriendProxyServiceImpl</span>(){}
    

    4. 

  4. 

    

    ​
    

    5. 

  5. 

    

        <span style="color:#770088">public</span> <span style="color:#000000">GirlfriendProxyServiceImpl</span>(<span style="color:#000000">Girlfriend</span> <span style="color:#000000">girlfriend</span>) {
    

    6. 

  6. 

    

            <span style="color:#770088">this</span>.<span style="color:#000000">girlfriend</span> <span style="color:#981a1a">=</span> <span style="color:#000000">girlfriend</span>;
    

    7. 

  7. 

    

        }
    

    8. 

  8. 

    

    ​
    

    9. 

  9. 

    

        <span style="color:#770088">public</span> <span style="color:#000000">Girlfriend</span> <span style="color:#000000">getGirlfriend</span>() {
    

    10. 

  10. 

    

            <span style="color:#770088">return</span> <span style="color:#000000">girlfriend</span>;
    

    11. 

  11. 

    

        }
    

    12. 

  12. 

    

    ​
    

    13. 

  13. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">void</span> <span style="color:#000000">setGirlfriend</span>(<span style="color:#000000">Girlfriend</span> <span style="color:#000000">girlfriend</span>) {
    

    14. 

  14. 

    

            <span style="color:#770088">this</span>.<span style="color:#000000">girlfriend</span> <span style="color:#981a1a">=</span> <span style="color:#000000">girlfriend</span>;
    

    15. 

  15. 

    

        }
    

    16. 

  16. 

    

    ​
    

    17. 

  17. 

    

        <span style="color:#555555">@Override</span>
    

    18. 

  18. 

    

        <span style="color:#770088">public</span> <span style="color:#000000">Girlfriend</span> <span style="color:#000000">findGirlFriend</span>() {
    

    19. 

  19. 

    

            <span style="color:#770088">return</span> <span style="color:#770088">this</span>.<span style="color:#000000">girlfriend</span>;
    

    20. 

  20. 

    

        }
    

    21. 

  21. 

    

    }</span></span>
    

    22.

3.1.2 Spring的xml配置

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333">    <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gf6"</span> <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"girlfriend"</span><span style="color:#117700">></span>
    

    2. 

  2. 

    

            <span style="color:#117700"><</span><span style="color:#117700">constructor-arg</span> <span style="color:#0000cc">type</span>=<span style="color:#aa1111">"double"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"1.73"</span> <span style="color:#117700">/></span>
    

    3. 

  3. 

    

            <span style="color:#117700"><</span><span style="color:#117700">constructor-arg</span> <span style="color:#0000cc">type</span>=<span style="color:#aa1111">""</span> <span style="color:#117700">></span>
    

    4. 

  4. 

    

                <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>硕士<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    5. 

  5. 

    

            <span style="color:#117700"></</span><span style="color:#117700">constructor-arg</span><span style="color:#117700">></span>
    

    6. 

  6. 

    

        <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span>
    

    7. 

  7. 

    

    ​
    

    8. 

  8. 

    

        <span style="color:#aa5500"><!--autowire表示自动装配 ：</span>
    

    9. 

  9. 

    

        <span style="color:#aa5500">byName 根据bean的名字去自动转配(name属性值需要跟构造方法中的name属性值一致)，</span>
    

    10. 

  10. 

    

         <span style="color:#aa5500">byType根据类型自动装配--></span>
    

    11. 

  11. 

    

        <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gfService"</span>
    

    12. 

  12. 

    

              <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span> <span style="color:#0000cc">autowire</span>=<span style="color:#aa1111">"byName"</span><span style="color:#117700">></span>
    

    13. 

  13. 

    

            <span style="color:#aa5500"><!--<property name="girlfriend" ></span>
    

    14. 

  14. 

    

                <span style="color:#aa5500"><ref bean="gf6"/></span>
    

    15. 

  15. 

    

            <span style="color:#aa5500"></property>--></span>
    

    16. 

  16. 

    

        <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span></span></span>
    

    17.

3.1.3 测试

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">class</span> <span style="color:#0000ff">TestGFServiceByName</span> {
    

    2. 

  2. 

    

        <span style="color:#770088">public</span> <span style="color:#770088">static</span> <span style="color:#008855">void</span> <span style="color:#000000">main</span>(<span style="color:#008855">String</span>[] <span style="color:#000000">args</span>) {
    

    3. 

  3. 

    

            <span style="color:#000000">ApplicationContext</span> <span style="color:#000000">ac</span> <span style="color:#981a1a">=</span> <span style="color:#770088">new</span> <span style="color:#000000">ClassPathXmlApplicationContext</span>(<span style="color:#aa1111">"application_context.xml"</span>);
    

    4. 

  4. 

    

            <span style="color:#000000">GirlfriendProxyServiceImpl</span> <span style="color:#000000">gfService</span> <span style="color:#981a1a">=</span> (<span style="color:#000000">GirlfriendProxyServiceImpl</span>) <span style="color:#000000">ac</span>.<span style="color:#000000">getBean</span>(<span style="color:#aa1111">"gfService"</span>);
    

    5. 

  5. 

    

            <span style="color:#000000">Girlfriend</span> <span style="color:#000000">girlfriend</span> <span style="color:#981a1a">=</span> <span style="color:#000000">gfService</span>.<span style="color:#000000">getGirlfriend</span>();
    

    6. 

  6. 

    

            <span style="color:#000000">System</span>.<span style="color:#000000">out</span>.<span style="color:#000000">println</span>(<span style="color:#000000">girlfriend</span>);
    

    7. 

  7. 

    

        }
    

    8. 

  8. 

    

    }</span></span>
    

    9.

运行结果：

 

如果将上述Spring的xml配置中的autowire属性值改成byType，表示根据类型自动装配，则会报如下错误！

3.2 全局自动注入

通过 beans 标签中的default-autowire  属性配置自动注入。

有效范围：配置文件中的所有 bean 标签都生效。

四、依赖注入的数据类型

1 注入 Bean 对象

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333">    <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gfService"</span>
    

    2. 

  2. 

    

              <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span> <span style="color:#0000cc">autowire</span>=<span style="color:#aa1111">"byType"</span><span style="color:#117700">></span>
    

    3. 

  3. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"girlfriend"</span> <span style="color:#117700">></span>
    

    4. 

  4. 

    

                <span style="color:#117700"><</span><span style="color:#117700">ref</span> <span style="color:#0000cc">bean</span>=<span style="color:#aa1111">"gf6"</span><span style="color:#117700">/></span>
    

    5. 

  5. 

    

            <span style="color:#117700"></</span><span style="color:#117700">property</span><span style="color:#117700">></span>
    

    6. 

  6. 

    

        <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span></span></span>
    

    7.

2 注入基本数据类型和字符串

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333">   <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gf1"</span> <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span>
    

    2. 

  2. 

    

              <span style="color:#0000cc">scope</span>=<span style="color:#aa1111">"prototype"</span> <span style="color:#0000cc">lazy-init</span>=<span style="color:#aa1111">"false"</span><span style="color:#117700">></span>
    

    3. 

  3. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"education"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"本科"</span> <span style="color:#117700">/></span>
    

    4. 

  4. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"hight"</span> <span style="color:#117700">></span>
    

    5. 

  5. 

    

                <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>1.65<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    6. 

  6. 

    

            <span style="color:#117700"></</span><span style="color:#117700">property</span><span style="color:#117700">></span>
    

    7. 

  7. 

    

        <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span></span></span>
    

    8.

3 注入 List

3.1 POJO

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">class</span> <span style="color:#0000ff">GirlfriendOYY</span> <span style="color:#770088">implements</span> <span style="color:#000000">Girlfriend</span> {
    

    2. 

  2. 

    

        <span style="color:#770088">private</span> <span style="color:#008855">double</span> <span style="color:#000000">hight</span>;
    

    3. 

  3. 

    

        <span style="color:#770088">private</span> <span style="color:#008855">String</span> <span style="color:#000000">education</span>;
    

    4. 

  4. 

    

        <span style="color:#770088">private</span> <span style="color:#000000">List</span><span style="color:#981a1a"><</span><span style="color:#008855">String</span><span style="color:#981a1a">></span> <span style="color:#000000">hobby</span>;     <span style="color:#aa5500">// 兴趣爱好</span>
    

    5. 

  5. 

    

        <span style="color:#770088">public</span> <span style="color:#000000">List</span><span style="color:#981a1a"><</span><span style="color:#008855">String</span><span style="color:#981a1a">></span> <span style="color:#000000">getHobby</span>() {
    

    6. 

  6. 

    

            <span style="color:#770088">return</span> <span style="color:#000000">hobby</span>;
    

    7. 

  7. 

    

        }
    

    8. 

  8. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">void</span> <span style="color:#000000">setHobby</span>(<span style="color:#000000">List</span><span style="color:#981a1a"><</span><span style="color:#008855">String</span><span style="color:#981a1a">></span> <span style="color:#000000">hobby</span>) {
    

    9. 

  9. 

    

            <span style="color:#770088">this</span>.<span style="color:#000000">hobby</span> <span style="color:#981a1a">=</span> <span style="color:#000000">hobby</span>;
    

    10. 

  10. 

    

        }    
    

    11. 

  11. 

    

        <span style="color:#555555">@Override</span>
    

    12. 

  12. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">String</span> <span style="color:#000000">toString</span>() {
    

    13. 

  13. 

    

            <span style="color:#770088">return</span> <span style="color:#aa1111">"GirlfriendOYY{"</span> <span style="color:#981a1a">+</span>
    

    14. 

  14. 

    

                    <span style="color:#aa1111">"hight="</span> <span style="color:#981a1a">+</span> <span style="color:#000000">hight</span> <span style="color:#981a1a">+</span>
    

    15. 

  15. 

    

                    <span style="color:#aa1111">", education='"</span> <span style="color:#981a1a">+</span> <span style="color:#000000">education</span> <span style="color:#981a1a">+</span> <span style="color:#aa1111">'\''</span> <span style="color:#981a1a">+</span>
    

    16. 

  16. 

    

                    <span style="color:#aa1111">", hobby="</span> <span style="color:#981a1a">+</span> <span style="color:#000000">hobby</span> <span style="color:#981a1a">+</span>
    

    17. 

  17. 

    

                    <span style="color:#aa1111">'}'</span>;
    

    18. 

  18. 

    

        }
    

    19. 

  19. 

    

    }</span></span>
    

    20.

3.2 Spring的xml配置

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333">   <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gf1"</span> <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span>
    

    2. 

  2. 

    

              <span style="color:#0000cc">scope</span>=<span style="color:#aa1111">"prototype"</span> <span style="color:#0000cc">lazy-init</span>=<span style="color:#aa1111">"false"</span><span style="color:#117700">></span>
    

    3. 

  3. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"education"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"本科"</span> <span style="color:#117700">/></span>
    

    4. 

  4. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"hight"</span> <span style="color:#117700">></span>
    

    5. 

  5. 

    

                <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>1.65<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    6. 

  6. 

    

            <span style="color:#117700"></</span><span style="color:#117700">property</span><span style="color:#117700">></span>
    

    7. 

  7. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"hobby"</span><span style="color:#117700">></span>
    

    8. 

  8. 

    

                <span style="color:#117700"><</span><span style="color:#117700">list</span><span style="color:#117700">></span>
    

    9. 

  9. 

    

                    <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>看电影<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    10. 

  10. 

    

                    <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>旅游<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    11. 

  11. 

    

                <span style="color:#117700"></</span><span style="color:#117700">list</span><span style="color:#117700">></span>
    

    12. 

  12. 

    

            <span style="color:#117700"></</span><span style="color:#117700">property</span><span style="color:#117700">></span>
    

    13. 

  13. 

    

        <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span></span></span>
    

    14.

3.3 测试

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">class</span> <span style="color:#0000ff">TestGirlfriend</span> {
    

    2. 

  2. 

    

        <span style="color:#770088">public</span> <span style="color:#770088">static</span> <span style="color:#008855">void</span> <span style="color:#000000">main</span>(<span style="color:#008855">String</span>[] <span style="color:#000000">args</span>) {
    

    3. 

  3. 

    

            <span style="color:#000000">ApplicationContext</span> <span style="color:#000000">ac</span> <span style="color:#981a1a">=</span> <span style="color:#770088">new</span> <span style="color:#000000">ClassPathXmlApplicationContext</span>(<span style="color:#aa1111">"application_context.xml"</span>);
    

    4. 

  4. 

    

            <span style="color:#000000">Girlfriend</span> <span style="color:#000000">gf</span> <span style="color:#981a1a">=</span> (<span style="color:#000000">Girlfriend</span>) <span style="color:#000000">ac</span>.<span style="color:#000000">getBean</span>(<span style="color:#aa1111">"gf1"</span>);
    

    5. 

  5. 

    

            <span style="color:#000000">System</span>.<span style="color:#000000">out</span>.<span style="color:#000000">println</span>(<span style="color:#000000">gf</span>);
    

    6. 

  6. 

    

        }
    

    7. 

  7. 

    

    }</span></span>
    

    8.

运行结果：

4 注入 Set

同上。

5 注入 Map

5.1 POJO修改

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333"><span style="color:#770088">public</span> <span style="color:#770088">class</span> <span style="color:#0000ff">GirlfriendOYY</span> <span style="color:#770088">implements</span> <span style="color:#000000">Girlfriend</span> {
    

    2. 

  2. 

    

        <span style="color:#770088">private</span> <span style="color:#008855">double</span> <span style="color:#000000">hight</span>;
    

    3. 

  3. 

    

        <span style="color:#770088">private</span> <span style="color:#008855">String</span> <span style="color:#000000">education</span>;
    

    4. 

  4. 

    

        <span style="color:#770088">private</span> <span style="color:#000000">List</span><span style="color:#981a1a"><</span><span style="color:#008855">String</span><span style="color:#981a1a">></span> <span style="color:#000000">hobby</span>;
    

    5. 

  5. 

    

        <span style="color:#770088">private</span> <span style="color:#000000">Map</span><span style="color:#981a1a"><</span><span style="color:#008855">String</span>, <span style="color:#008855">String</span><span style="color:#981a1a">></span> <span style="color:#000000">parents</span>;    <span style="color:#aa5500">// 父母情况</span>
    

    6. 

  6. 

    

        <span style="color:#770088">public</span> <span style="color:#000000">Map</span><span style="color:#981a1a"><</span><span style="color:#008855">String</span>, <span style="color:#008855">String</span><span style="color:#981a1a">></span> <span style="color:#000000">getParents</span>() {
    

    7. 

  7. 

    

            <span style="color:#770088">return</span> <span style="color:#000000">parents</span>;
    

    8. 

  8. 

    

        }
    

    9. 

  9. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">void</span> <span style="color:#000000">setParents</span>(<span style="color:#000000">Map</span><span style="color:#981a1a"><</span><span style="color:#008855">String</span>, <span style="color:#008855">String</span><span style="color:#981a1a">></span> <span style="color:#000000">parents</span>) {
    

    10. 

  10. 

    

            <span style="color:#770088">this</span>.<span style="color:#000000">parents</span> <span style="color:#981a1a">=</span> <span style="color:#000000">parents</span>;
    

    11. 

  11. 

    

        }
    

    12. 

  12. 

    

    ​
    

    13. 

  13. 

    

        <span style="color:#555555">@Override</span>
    

    14. 

  14. 

    

        <span style="color:#770088">public</span> <span style="color:#008855">String</span> <span style="color:#000000">toString</span>() {
    

    15. 

  15. 

    

            <span style="color:#770088">return</span> <span style="color:#aa1111">"GirlfriendOYY{"</span> <span style="color:#981a1a">+</span>
    

    16. 

  16. 

    

                    <span style="color:#aa1111">"hight="</span> <span style="color:#981a1a">+</span> <span style="color:#000000">hight</span> <span style="color:#981a1a">+</span>
    

    17. 

  17. 

    

                    <span style="color:#aa1111">", education='"</span> <span style="color:#981a1a">+</span> <span style="color:#000000">education</span> <span style="color:#981a1a">+</span> <span style="color:#aa1111">'\''</span> <span style="color:#981a1a">+</span>
    

    18. 

  18. 

    

                    <span style="color:#aa1111">", hobby="</span> <span style="color:#981a1a">+</span> <span style="color:#000000">hobby</span> <span style="color:#981a1a">+</span>
    

    19. 

  19. 

    

                    <span style="color:#aa1111">", parents="</span> <span style="color:#981a1a">+</span> <span style="color:#000000">parents</span> <span style="color:#981a1a">+</span>
    

    20. 

  20. 

    

                    <span style="color:#aa1111">'}'</span>;
    

    21. 

  21. 

    

        }
    

    22. 

  22. 

    

    }</span></span>
    

    23.

5.2 Spring的xml配置修改

    

  1. 

    

    <span style="background-color:#f8f8f8"><span style="color:#333333">    <span style="color:#117700"><</span><span style="color:#117700">bean</span> <span style="color:#0000cc">id</span>=<span style="color:#aa1111">"gf1"</span> <span style="color:#0000cc">class</span>=<span style="color:#aa1111">""</span>
    

    2. 

  2. 

    

              <span style="color:#0000cc">scope</span>=<span style="color:#aa1111">"prototype"</span> <span style="color:#0000cc">lazy-init</span>=<span style="color:#aa1111">"false"</span><span style="color:#117700">></span>
    

    3. 

  3. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"education"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"本科"</span> <span style="color:#117700">/></span>
    

    4. 

  4. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"hight"</span> <span style="color:#117700">></span>
    

    5. 

  5. 

    

                <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>1.65<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    6. 

  6. 

    

            <span style="color:#117700"></</span><span style="color:#117700">property</span><span style="color:#117700">></span>
    

    7. 

  7. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"hobby"</span><span style="color:#117700">></span>
    

    8. 

  8. 

    

                <span style="color:#117700"><</span><span style="color:#117700">list</span><span style="color:#117700">></span>
    

    9. 

  9. 

    

                    <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>看电影<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    10. 

  10. 

    

                    <span style="color:#117700"><</span><span style="color:#117700">value</span><span style="color:#117700">></span>旅游<span style="color:#117700"></</span><span style="color:#117700">value</span><span style="color:#117700">></span>
    

    11. 

  11. 

    

                <span style="color:#117700"></</span><span style="color:#117700">list</span><span style="color:#117700">></span>
    

    12. 

  12. 

    

            <span style="color:#117700"></</span><span style="color:#117700">property</span><span style="color:#117700">></span>
    

    13. 

  13. 

    

            <span style="color:#117700"><</span><span style="color:#117700">property</span> <span style="color:#0000cc">name</span>=<span style="color:#aa1111">"parents"</span> <span style="color:#117700">></span>
    

    14. 

  14. 

    

                <span style="color:#117700"><</span><span style="color:#117700">map</span><span style="color:#117700">></span>
    

    15. 

  15. 

    

                    <span style="color:#117700"><</span><span style="color:#117700">entry</span> <span style="color:#0000cc">key</span>=<span style="color:#aa1111">"father"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"zs"</span> <span style="color:#117700">/></span>
    

    16. 

  16. 

    

                    <span style="color:#117700"><</span><span style="color:#117700">entry</span> <span style="color:#0000cc">key</span>=<span style="color:#aa1111">"mother"</span> <span style="color:#0000cc">value</span>=<span style="color:#aa1111">"ls"</span> <span style="color:#117700">/></span>
    

    17. 

  17. 

    

                <span style="color:#117700"></</span><span style="color:#117700">map</span><span style="color:#117700">></span>
    

    18. 

  18. 

    

            <span style="color:#117700"></</span><span style="color:#117700">property</span><span style="color:#117700">></span>
    

    19. 

  19. 

    

         <span style="color:#117700"></</span><span style="color:#117700">bean</span><span style="color:#117700">></span></span></span>
    

    20.

测试类不用修改，运行结果：

6 注入Properties

略。

总结

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