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Spring2.5依赖注入方式(DI)

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Spring2.5依赖注入的方式有三种:

  1. 通过setter方法注入;
  2. 通过构造方法注入;
  3. 通过注解进行注入;

第一种方式:通过setter方法注入

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 version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:lang="http://www.springframework.org/schema/lang"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-2.0.xsd">
	<bean id="userdao" class="com.test.UserDaoImplement"></bean>
	<bean id="userservice" class="com.test.UserServiceImplement">
		<property name="user" ref="userdao"></property>
	</bean>
</beans>

 

 注意这种方法还可以把XML改成以下方式:

 

<?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:lang="http://www.springframework.org/schema/lang"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-2.0.xsd">
	<bean id="userservice" class="com.test.UserServiceImplement"> <!-- <property name="user" ref="userdao"></property>-->
		<property name="user">
			<bean class="com.test.UserDaoImplement"></bean>
		</property>
	</bean>
</beans>

 

这两者的区别在于,第二种方式只会注入到当前这个Bean实例中,而不能再注入到其它的Bean中,第一种方式被注入的Bean可以注入到多个Bean当中,这可能会有一些线程安全的问题,因此在最好指定被注入的Bean的作用域。

 

另外通过setter方式注入,对应的注入依赖属性,必须要有setter方法。

 

 

 

测试代码:

package com.test;

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

public class Test {
	public static void main(String[] args) {
		ApplicationContext ctx = new ClassPathXmlApplicationContext(
				"com/test/bean.xml");
		IUserService us = (IUserService) ctx.getBean("userservice");
		us.saveUser();
	}
}

 

第二种方式:通过构造方法进行注入

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);
	}
}

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:lang="http://www.springframework.org/schema/lang"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-2.0.xsd">
	<bean id="userdao" class="com.test.UserDaoImplement"></bean>
	<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>

 

 

 

 

注意

  • <construcotr-arg>标签中的index属性如果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,如果有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,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,如果是一个接口,那么也不允许传它的实现类,这是一个可选属性;
  • 如果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;
  • 同样要注意bean的作用域问题。

 测试代码同上......

 

第三种方式:通过java注解进行注入

 

使用这种方式进行注入可以用两个标注:

  • @Resource
  • @Autowired

两者的区别:1. @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;

                  2. @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;

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

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

 

I.使用@Resource标注进行注入

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 version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans 
           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-2.5.xsd">
	<context:annotation-config />

	<bean id="user" class="com.test.UserDaoImplement"></bean>
	<bean id="user1" class="com.test.UserDaoImplement"></bean>
	<bean id="userservice" class="com.test.UserServiceImplement"></bean>
</beans>

 

 测试类:

package com.test;

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

public class Test {

	public static void main(String[] args) {
		ApplicationContext ctx = new ClassPathXmlApplicationContext(
				"com/test/bean.xml");
		IUserService us = (IUserService) ctx.getBean("userservice");
		us.saveUser();
	}
}

 

II.使用@Autowired

 

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 version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans 
           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-2.5.xsd">
	<context:annotation-config />

	<bean id="user" class="com.test.UserDaoImplement"></bean>
	<bean id="userservice" class="com.test.UserServiceImplement"></bean>
</beans>

 测试类:

package com.test;

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

public class Test {

	public static void main(String[] args) {
		ApplicationContext ctx = new ClassPathXmlApplicationContext(
				"com/test/bean.xml");
		IUserService us = (IUserService) ctx.getBean("userservice");
		us.saveUser();
	}
}

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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