Spring-注解方式 IOC/DI

在本知识点中，讲演示如何使用注解的方式完成注入对象中的效果

修改applicationContext.xml

1. 在15行添加

<context:annotation-config/>

表示告诉Spring要用注解的方式进行配置

2. 注入对象的21行注释掉，这个行为在后面将使用注解来完成

<?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:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">

<context:annotation-config/>
<bean name="c" class="com.how2java.pojo.Category">
<property name="name" value="category 1" />
</bean>
<bean name="p" class="com.how2java.pojo.Product">
<property name="name" value="product1" />
<!--         <property name="category" ref="c" /> -->
</bean>

</beans>

@Autowired

在Product.java的category属性前加上@Autowired注解

@Autowired
private Category category;

package com.how2java.pojo;

import org.springframework.beans.factory.annotation.Autowired;

public class Product {

private int id;
private String name;
@Autowired
private Category category;

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 Category getCategory() {
return category;
}

public void setCategory(Category category) {
this.category = category;
}
}

运行测试

package com.how2java.test;

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

import com.how2java.pojo.Product;

public class TestSpring {

public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext(new String[] { "applicationContext.xml" });
Product p = (Product) context.getBean("p");
System.out.println(p.getName());
System.out.println(p.getCategory().getName());
}
}

@Autowired的位置

除了前面的 在属性前加上@Autowired 这种方式外，也可以在setCategory方法前加上@Autowired，这样来达到相同的效果

@Autowired
public void setCategory(Category category)

package com.how2java.pojo;

import org.springframework.beans.factory.annotation.Autowired;

public class Product {

private int id;
private String name;

private Category category;

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 Category getCategory() {
return category;
}
@Autowired
public void setCategory(Category category){
this.category = category;
}
}

@Resource

除了@Autowired之外，@Resource也是常用的手段

@Resource(name="c")
private Category category;

 

package com.how2java.pojo;

import javax.annotation.Resource;

public class Product {

private int id;
private String name;
@Resource(name="c")
private Category category;

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 Category getCategory() {
return category;
}

public void setCategory(Category category) {
this.category = category;
}
}

对Bean的注解

上述例子是对注入对象行为的注解，那么bean对象本身，比如Category,Product可不可以移出applicationContext.xml配置文件，也通过注解进行呢？

接下来就讲解如何对Bean进行注解配置
applicationContext.xml

修改applicationContext.xml，什么都去掉，只新增：

<context:component-scan base-package="com.how2java.pojo"/>

其作用是告诉Spring，bean都放在com.how2java.pojo这个包下

<?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:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">

<context:component-scan base-package="com.how2java.pojo"/>

</beans>

@Component

为Product类加上@Component注解，即表明此类是bean

@Component("p")
public class Product {

为Category 类加上@Component注解，即表明此类是bean

@Component("c")
public class Category {

另外，因为配置从applicationContext.xml中移出来了，所以属性初始化放在属性声明上进行了。

private String name="product 1";
private String name="category 1";

package com.how2java.pojo;

import javax.annotation.Resource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component("p")
public class Product {

private int id;
private String name="product 1";

@Autowired
private Category category;

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 Category getCategory() {
return category;
}

public void setCategory(Category category) {
this.category = category;
}
}

package com.how2java.pojo;

import org.springframework.stereotype.Component;

@Component("c")
public class Category {

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;
}
private int id;
private String name="category 1";
}

运行测试

运行TestSpring，可以发现运行结果是一样的

package com.how2java.test;

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

import com.how2java.pojo.Product;

public class TestSpring {

public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext(new String[] { "applicationContext.xml" });
Product p = (Product) context.getBean("p");
Syst
4000
em.out.println(p.getName());
System.out.println(p.getCategory().getName());
}
}