1,Set注入 2,构造注入
Set方法注入:
原理:通过类的setter方法完成依赖关系的设置
name属性的取值依setter方法名而定,要求这个类里面这个对应的属性必须有setter方法。
Set方法注入时spring中配置文件:
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<? xml version = "1.0" encoding = "UTF-8" ?>
< beans
xmlns = "http://www.springframework.org/schema/beans"
xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
xmlns:p = "http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
< bean id = "car" class = "org.spring01.Car" >
< constructor-arg value = "奔驰" ></ constructor-arg >
< constructor-arg type = "java.lang.String" >
< value >土豪金</ value >
</ constructor-arg >
< constructor-arg value = "高级轿车" ></ constructor-arg >
</ bean >
< bean id = "person" class = "org.spring01.Person" >
< property name = "name" value = "张三" ></ property >
< property name = "age" value = "11" ></ property >
< property name = "car" ref = "car" ></ property >
</ bean >
</ beans >
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定义Car类:
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package org.spring01;
public class Car {
private String name; //车名
private String color; //颜色
private String clas; //等级
public String getName() {
return name;
}
public void setName(String name) {
this .name = name;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this .color = color;
}
public String getClas() {
return clas;
}
public void setClas(String clas) {
this .clas = clas;
}
public Car(String name, String color, String clas) {
super ();
this .name = name;
this .color = color;
this .clas = clas;
}
public Car() {
super ();
// TODO Auto-generated constructor stub
}
@Override
public String toString() {
return "Car [name=" + name + ", color=" + color + ", clas=" + clas
+ "]" ;
}
}
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定义Person类:
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package org.spring01;
public class Person {
private String name; //名字
private int age; //年龄
private Car car; //他的车
public String getName() {
return name;
}
public void setName(String name) {
this .name = name;
}
public int getAge() {
return age;
}
public void setAge( int age) {
this .age = age;
}
public Car getCar() {
return car;
}
public void setCar(Car car) {
this .car = car;
}
public Person(String name, int age, Car car) {
super ();
this .name = name;
this .age = age;
this .car = car;
}
public Person() {
super ();
// TODO Auto-generated constructor stub
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + ", car=" + car + "]" ;
}
}
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测试类:
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package org.spring01;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class SpringTest{
@Test
public void toGetPerson(){
ApplicationContext context = new ClassPathXmlApplicationContext( "applicationContext.xml" );
Person person = (Person) context.getBean( "person" );
System.out.println(person);
}
@Test
public void toGetCar(){
ApplicationContext context = new ClassPathXmlApplicationContext( "applicationContext.xml" );
Car car = (Car) context.getBean( "car" );
System.out.println(car);
}
}
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使用单元测试(JUnit)测试toGetPerson()方法,结果为:
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Person [name=张三, age=11, car=Car [name=奔驰, color=土豪金, clas=高级轿车]]
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构造方法注入:
原理:通过构造函数完成依赖关系的设定
构造注入指的是在接受注入的类中,定义一个构造方法,并在构造方法的参数中定义需要注入的元素,其中,index表示构造方法中的参数索引(第一个参数索引为0)。
构造方法注入时spring中配置文件:
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<? xml version = "1.0" encoding = "UTF-8" ?>
< beans
xmlns = "http://www.springframework.org/schema/beans"
xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
xmlns:p = "http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
< bean id = "car" class = "org.spring02.Car" >
< constructor-arg value = "大众" ></ constructor-arg >
< constructor-arg type = "java.lang.String" >
< value >白色</ value >
</ constructor-arg >
< constructor-arg value = "中级轿车" ></ constructor-arg >
</ bean >
< bean id = "person" class = "org.spring02.Person" >
< constructor-arg index = "0" value = "李四" ></ constructor-arg >
< constructor-arg index = "1" value = "23" ></ constructor-arg >
< constructor-arg index = "2" ref = "car" ></ constructor-arg >
</ bean >
</ beans >
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定义Car类:
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package org.spring02;
public class Car {
private String name; //车名
private String color; //颜色
private String clas; //等级
public Car(String name, String color, String clas) {
super ();
this .name = name;
this .color = color;
this .clas = clas;
}
public Car() {
super ();
// TODO Auto-generated constructor stub
}
@Override
public String toString() {
return "Car [name=" + name + ", color=" + color + ", clas=" + clas
+ "]" ;
}
}
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定义Person类:
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package org.spring02;
public class Person {
private String name; //名字
private int age; //年龄
private Car car; //他的车
public Person(String name, int age, Car car) {
super ();
this .name = name;
this .age = age;
this .car = car;
}
public Person() {
super ();
// TODO Auto-generated constructor stub
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + ", car=" + car + "]" ;
}
}
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测试类:
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package org.spring02;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class SpringTest{
@Test
public void toGetPerson(){
ApplicationContext context = new ClassPathXmlApplicationContext( "applicationContext01.xml" );
Person person = (Person) context.getBean( "person" );
System.out.println(person);
}
@Test
public void toGetCar(){
ApplicationContext context = new ClassPathXmlApplicationContext( "applicationContext01.xml" );
Car car = (Car) context.getBean( "car" );
System.out.println(car);
}
}
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使用单元测试(JUnit)测试toGetPerson()方法,结果为:
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Person [name=李四, age=23, car=Car [name=大众, color=白色, clas=中级轿车]]
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上面的例子都采用了单元测试的方法检测运行结果,需要导库: JUnit
Demo的大体结构:
我们可以看到,set方法和构造方法都可以设值成功, 实际开发中最常用到的是set方法设值。但这两种依赖注入的方式并没有绝对的好坏,只是使用的场合不同。
使用构造注入可以在构建对象的同时完成依赖关系到的建立,所以如果要建立的对象的关系很多,使用构造注入会在构造方法上留下很多参数,可读性极差,所以当对象的关系比较多的时候采用set方法注入。
使用set方法注入是通过类的setter方法完成依赖关系的设置的,所以不能保证相关的数据在执行时不被更改设定。所以如果想使一些数据变为只读或者私有,就要采用构造注入了。
建议采用以set注入为主,构造注入为辅的注入策略。对于依赖关系无须变化的注入,尽量采用构造注入;而其他的依赖关系的注入,则考虑采用set注入。
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。
原文链接:http://blog.csdn.net/weixin_36380516/article/details/72301260?utm_source=tuicool&utm_medium=referral