8Spring初步----青软S2SH(笔记)

例子:

bean.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans
    xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
          http://www.springframework.org/schema/beans/spring-beans-4.1.xsd">
    <bean id="book" class="com.qst.chapter08.Book">
        <property name="name" value="SSH开发" />
        <property name="author" value="qst" />
        <property name="publishHouse" value="某出版社" />
        <property name="price" value="70.25" />
    </bean>
</beans>

测试代码

import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
import org.springframework.core.io.ClassPathResource;

public class BeanFactoryExample {

    public static void main(String[] args) {
        // 根据配置文件创建ClassPathResource对象
        ClassPathResource resource = new ClassPathResource("com/qst/chapter08/bean.xml");
        // 创建BeanFactory对象
        DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
        XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
        reader.loadBeanDefinitions(resource);
        // 从BeanFactory对象中，根据id获取具体对象
        Book book = (Book) factory.getBean("book");

        System.out.println(book.getName());
        System.out.println(book.getAuthor());
        System.out.println(book.getPublishHouse());
        System.out.println(book.getPrice());
    }
}

ApplicationContext的例子

public class ApplicationContextExample {

    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("com/qst/chapter08/bean.xml");
        Book book = (Book) context.getBean("book");

        System.out.println(book.getName());
        System.out.println(book.getAuthor());
        System.out.println(book.getPublishHouse());
        System.out.println(book.getPrice());

        context.close();
    }
}

例如

<?xml version="1.0" encoding="UTF-8"?>
<beans
    xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
          http://www.springframework.org/schema/beans/spring-beans-4.1.xsd">
　　<!--配置bean-->
</beans>

测试类不变,需要改变bean和配置文件,测试类里的调用方法不变:

bean中加一个构造方法,配置文件中加入这个构造方法的相关配置

public class Order {
    private int id;
    private String orderNo; // 订单编号
    private double amount; // 订单金额

    private Object[] myArray;
    private List<?> myList;
    private Set<?> mySet;
    private Map<?, ?> myMap;
    private Properties myProp;

    public Order(int id, String orderNo) {
        this.id = id;
        this.orderNo = orderNo;
    }
　　//其他省略

}

   <bean id="order" class="com.qst.chapter08.config.Order">
<constructor-arg name="id" value="100" />
        <constructor-arg name="orderNo">
            <value>ABCDEF</value>
        </constructor-arg>
        <property name="amount">
            <value>5678.123</value>
        </property>

        <!--其他省略-->
    </bean>    

示例如下:

public class Order {
    private int id;
    private String orderNo; // 订单编号
    private double amount; // 订单金额

    private Object[] myArray;
    private List<?> myList;
    private Set<?> mySet;
    private Map<?, ?> myMap;
    private Properties myProp;

    public Order(int id, String orderNo) {
        this.id = id;
        this.orderNo = orderNo;
    }

    public int getId() {
        return id;
    }

    public String getOrderNo() {
        return orderNo;
    }

    public void setOrderNo(String orderNo) {
        this.orderNo = orderNo;
    }

    public double getAmount() {
        return amount;
    }

    public void setAmount(double amount) {
        this.amount = amount;
    }

    public Object[] getMyArray() {
        return myArray;
    }

    public void setMyArray(Object[] myArray) {
        this.myArray = myArray;
    }

    public List<?> getMyList() {
        return myList;
    }

    public void setMyList(List<?> myList) {
        this.myList = myList;
    }

    public Set<?> getMySet() {
        return mySet;
    }

    public void setMySet(Set<?> mySet) {
        this.mySet = mySet;
    }

    public Map<?, ?> getMyMap() {
        return myMap;
    }

    public void setMyMap(Map<?, ?> myMap) {
        this.myMap = myMap;
    }

    public Properties getMyProp() {
        return myProp;
    }

    public void setMyProp(Properties myProp) {
        this.myProp = myProp;
    }

}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
          http://www.springframework.org/schema/beans/spring-beans-4.1.xsd">
    <bean id="order" class="com.qst.chapter08.config.Order">
        <constructor-arg name="id" value="100" />
        <constructor-arg name="orderNo">
            <value>ABCDEF</value>
        </constructor-arg>
        <property name="amount">
            <value>5678.123</value>
        </property>

        <property name="myArray">
            <array>
                <value>1234</value>
                <ref bean="orderItem1" />
            </array>
        </property>

        <property name="myList">
            <list>
                <value>1234</value>
                <ref bean="orderItem1" />
            </list>
        </property>

        <property name="mySet">
            <set>
                <value>1234</value>
                <ref bean="orderItem1" />
            </set>
        </property>

        <property name="myMap">
            <map>
                <entry key="1" value="1234" />
                <entry key="2" value-ref="orderItem1" />
            </map>
        </property>

        <property name="myProp">
            <props>
                <prop key="aaa">AAA</prop>
                <prop key="bbb">BBBBB</prop>
            </props>
        </property>
    </bean>

    <bean id="orderItem1" class="com.qst.chapter08.config.OrderItem" >
        <property name="id" value="1" />
        <property name="product" value="电视机" />
        <property name="price" value="3000" />
        <property name="count" value="4" />
    </bean>

</beans>

这里的继承指的是配置信息的重用,跟面向对象里的继承毫无关系.

前置依赖是指,有时要求Bean A的初始化必须在Bean B的初始化之后,而B并不是A的属性.这种情况下,无法通过ref来保证B先初始化,所以Spring提供了depends-on.

这里重点说一下by Type,by Type方式只根据类型与否匹配来决定是否注入依赖关系,加入A实例有setB(B b)方法,而Spring配置文件中恰好有一个类型B的Bean实例,则Spring会注入此实例,如果容器总没有一个类型为B的实例或多于一个的B实例,则都会抛出异常.