J2EE系列之Spring4学习笔记（三）--IOC详解（依赖注入）

现在讲一下如何通过Spring装配一个对象实例，并给对象中的属性赋值。

1.新建一个工程：Spring402-02

2.新建一个类People：

package com.test.entity;

public class People {

private int id;
private String name;
private int age;

public People() {
super();
// TODO Auto-generated constructor stub
}

public People(int id, String name, int age) {
super();
this.id = id;
this.name = name;
this.age = age;
}

public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
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;
}
@Override
public String toString() {
return "People [id=" + id + ", name=" + name + ", age=" + age + "]";
}

}

这里定义了几个属性，并生成了People类的两个构造函数。
3.装配一个bean，Spring配置文件为：

<?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.xsd">
<bean id="people" class="com.test.entity.People"></bean>

</beans>
4.写测试方法：
package com.test.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.test.entity.People;

public class Test {

public static void main(String[] args) {

ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
People people = (People) ac.getBean("people");
System.out.println(people);

}
}


运行这个测试方法：



这里我们在配置文件中只是生成了一个简单的People类对象，并没有给对象中的属性赋值。

下面通过几种不同的方法给People对象的属性注入值。

1.属性注入方法

修改Spring配置文件，里面生成一个新的People对象：

<bean id="people2" class="com.test.entity.People">
<property name="id" value="1"></property>
<property name="name" value="张三"></property>
<property name="age" value="11"></property>
</bean>这里使用了属性注入方法来生成一个新的People对象实例，使用<property>标签给各个属性赋值。
修改测试方法：

public class Test {

public static void main(String[] args) {

ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
People people = (People) ac.getBean("people");
System.out.println(people);

People people2 = (People) ac.getBean("people2");
System.out.println(people2);

}
}

运行测试方法：



可以看到这里的第二个对象people2中各个属性已经有值了。

2.构造函数注入（通过类型）

People类中我们生成了有参的构造函数，这里通过构造函数中各个形参的类型类给对象注入值。修改Spring配置文件，添加一个新的bean：

<bean id="people3" class="com.test.entity.People">
<constructor-arg type="int" value="2"></constructor-arg>
<constructor-arg type="String" value="李四"></constructor-arg>
<constructor-arg type="int" value="22"></constructor-arg>
</bean>这里我们通过有参的构造函数来给各个属性赋值。
修改测试方法为：

public static void main(String[] args) {

ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
People people = (People) ac.getBean("people");
System.out.println(people);

People people2 = (People) ac.getBean("people2");
System.out.println(people2);

People people3 = (People) ac.getBean("people3");
System.out.println(people3);

}

运行测试方法：



可以看到这里生成的新的People对象people3中的各个属性也是有值的。

3.构造方法注入（通过索引）

上面的注入方法是通过构造函数中各个形参的类型完成的，现在来通过各个形参的索引完成注入。修改Spring配置文件，生成一个新的bean：

<bean id="people4" class="com.test.entity.People">
<constructor-arg index="0" value="3"></constructor-arg>
<constructor-arg index="1" value="王五"></constructor-arg>
<constructor-arg index="2" value="33"></constructor-arg>
</bean>

这里通过构造函数中各个形参的索引值来注入值。
修改测试方法：

public static void main(String[] args) {

ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
People people = (People) ac.getBean("people");
System.out.println(people);

People people2 = (People) ac.getBean("people2");
System.out.println(people2);

People people3 = (People) ac.getBean("people3");
System.out.println(people3);

People people4 = (People) ac.getBean("people4");
System.out.println(people4);

}

运行测试方法：



这里通过索引注入了值。

4.构造函数注入（联合使用）

所谓的联合使用就是把类型和索引两者联合在一起。修改Spring配置文件，生成一个新的bean：

<bean id="people5" class="com.test.entity.People">
<constructor-arg index="0" type="int" value="4"></constructor-arg>
<constructor-arg index="1" type="String" value="赵六"></constructor-arg>
<constructor-arg index="2" type="int" value="44"></constructor-arg>
</bean>

修改测试方法为：
public static void main(String[] args) {

ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
People people = (People) ac.getBean("people");
System.out.println(people);

People people2 =
4000
(People) ac.getBean("people2");
System.out.println(people2);

People people3 = (People) ac.getBean("people3");
System.out.println(people3);

People people4 = (People) ac.getBean("people4");
System.out.println(people4);

People people5 = (People) ac.getBean("people5");
System.out.println(people5);

}

运行测试方法：



5.使用非静态工厂注入

这种方式首先要建一个工厂类负责生成People类的对象。新建一个工厂类PeopleFactory：

package com.test.factory;

import com.test.entity.People;

public class PeopleFactory {

public People createPeople(){
People p = new People();
p.setId(5);
p.setName("七七");
p.setAge(55);
return p;
}
}

这个工厂类中有个非静态的方法createPeople来生成一个people对象，因为生成方法是非静态的，所以这个注入方法叫非静态工厂注入。

修改Spring配置文件，生成一个新的bean：

<bean id="peopleFactory" class="com.test.factory.PeopleFactory">
</bean>

<bean id="people7" factory-bean="peopleFactory" factory-method="createPeople"></bean>

这里第一个<bean>生成了一个造人工厂类的实例对象，第二个<bean>表示使用造人工厂中的createPeople方法返回的结果。
修改测试方法：

public static void main(String[] args) {

ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
People people = (People) ac.getBean("people");
System.out.println(people);

People people2 = (People) ac.getBean("people2");
System.out.println(people2);

People people3 = (People) ac.getBean("people3");
System.out.println(people3);

People people4 = (People) ac.getBean("people4");
System.out.println(people4);

People people5 = (People) ac.getBean("people5");
System.out.println(people5);

People people7 = (People) ac.getBean("people7");
System.out.println(people7);

}运行测试方法：



这里通过非静态工厂方法给新的People对象注入了值。

6.使用静态工厂方法注入

这里所谓的静态工厂就是指生成People对象的方法为静态方法。

新建一个造人工厂类：

package com.test.factory;

import com.test.entity.People;

public class PeopleFactory2 {

public static People createPeople(){
People p = new People();
p.setId(6);
p.setName("八");
p.setAge(66);
return p;
}
}

这里的createPeople方法为静态方法。
修改Spring配置文件，使用静态工厂方法给一个新的bean赋值：

<bean id="people8" class="com.test.factory.PeopleFactory2" factory-method="createPeople"></bean>

这里的方法为静态方法，直接使用类名.方法名的方式调用该静态方法。这里使用people8代表静态方法createPeople返回的结果。
修改测试方法：

public static void main(String[] args) {

ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
People people = (People) ac.getBean("people");
System.out.println(people);

People people2 = (People) ac.getBean("people2");
System.out.println(people2);

People people3 = (People) ac.getBean("people3");
System.out.println(people3);

People people4 = (People) ac.getBean("people4");
System.out.println(people4);

People people5 = (People) ac.getBean("people5");
System.out.println(people5);

People people7 = (People) ac.getBean("people7");
System.out.println(people7);

People people8 = (People) ac.getBean("people8");
System.out.println(people8);
}

运行测试方法：



这里通过静态工厂方法给People对象的属性进行了赋值。