Spring中Ioc容器的注入方式

1 通过setter方法注入

bean类：

package com.test;

public class UserServiceImplement implements IUserService

{
private IUserDao user;

public IUserDao getUser() {
return user;
}

public void setUser(IUserDao user) {
this.user = user;
}

public void saveUser() {
user.addUser();
}
}

Xml代码：

<?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:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd http://www.springframework.org/schema/mvc  http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd"> <bean id="userdao" class="com.test.UserDaoImplement"/>
<bean id="userservice" class="com.test.UserServiceImplement">
<property name="user" ref="userdao" />
</bean>
</beans>

注：setter方式注入，对应的注入依靠属性，必须要有setter方法。

2 通过构造方法注入

bean类：

package com.test;

public class UserServiceImplement implements IUserService {
private IUserDao user;
int age;

public UserServiceImplement(IUserDao user, int age) {
this.user = user;
this.age = age;
}

public void saveUser() {
user.addUser();
System.out.println(this.age);
}
}

xml代码：

<?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:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd http://www.springframework.org/schema/mvc  http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd"> <bean id="userdao" class="com.test.UserDaoImplement" />
<bean id="userservice" class="com.test.UserServiceImplement">
<constructor-arg index="0" type="com.test.IUserDao" ref="userdao"></constructor-arg>
<constructor-arg index="1" value="24"></constructor-arg>
</bean>
</beans>

注：

对于<construcotr-arg>标签中的index属性，假如构造方法只有一个参数的时候可以不指定；它的下标从0开始，表示构造方法参数的索引；假如构造方法有多个参数必须指定索引。除此之外还有一个type属性，type是一个可选属性，这个属性用来指定被注入的参数的参数类型，一定要跟构造方法中的参数类型一致，假如是一个接口，那么也不应传它的实现类。

假如构造函数的的参数类型是基本数据类型，那么就不用ref属性了，而用value属性设置它的值，而且这些数据类型会自动打包和解包；

要注意bean的作用域问题。

被注入的bean类，一定要有构造方法。

3 通过注解进行注入

@Resource
@Autowired

二者区别：

@Resource标注是由JDK提供的，而@Autowired标注是由Spring提供的，因而@Autowired标注会与Spring紧密耦合，所以推荐使用@Resource标注

@Resource默认是按照名称来装配注入的，当找不到与名称匹配的bean才会按照类型来装配注入

@Autowired默认是按照类型装配注入的，假如想按照名称来转配注入，则需要结合@Qualifier一起使用

@Resource和@Autowired都可以用来标注字段或者setter方法

@Resource注入方式代码：

package com.test;

import javax.annotation.Resource;

public class UserServiceImplement implements IUserService {

@Resource
private IUserDao user;

private IUserDao user1;

public IUserDao getUser1() {
return user1;
}

@Resource
public void setUser1(IUserDao user1) {
this.user1 = user1;
}

public void saveUser() {
user.addUser();
System.out.println("user注入成功");
user1.addUser();
System.out.println("user1注入成功");
}
}

xml文件：

<?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:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd http://www.springframework.org/schema/mvc  http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd"> <context:annotation-config />
<bean id="user" class="com.test.UserDaoImplement"/>
<bean id="user1" class="com.test.UserDaoImplement"/>
<bean id="userservice" class="com.test.UserServiceImplement"/>
</beans>

@Autowired注入方式代码：

package com.test;

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

public class UserServiceImplement implements IUserService {

@Autowired
private IUserDao user;

public IUserDao getUser() {
return user;
}

public void setUser(IUserDao user) {
this.user = user;
}

public void saveUser() {
user.addUser();
System.out.println("user注入成功");
}
}

xml文件：

<?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:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd http://www.springframework.org/schema/mvc  http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd"> <context:annotation-config />
<bean id="user" class="com.test.UserDaoImplement"/>
<bean id="userservice" class="com.test.UserServiceImplement"/>
</beans>