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

1. @Resource
2. @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>