第五章诠释的注入

第五章注释的注入

一：注释的方法注入

1.XML配置文件的改动：

<?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/>     
</beans>

2.依赖包的导入：

aopalliance.jar

asm-2.2.3.jar

asm-commons-2.2.3.jar

asm-util-2.2.3.jar

aspectjlib.jar

aspectjrt.jar

aspectjweaver.jar

cglib-nodep-2.1_3.jar

commons-attributes-api.jar

commons-attributes-compiler.jar

commons-logging.jar

log4j-1.2.15.jar

persistence.jar

spring-agent.jar

spring-aop.jar

spring-aspects.jar

spring-beans.jar

spring-context.jar

spring-core.jar

spring-jdbc.jar

spring-jms.jar

spring-orm.jar

spring-tomcat-weaver.jar

spring-tx.jar

二：@Autowired或 @Resource注释方式进行装配

@Autowired是默认按类型装配。

@Resource是默认按名称装配，找不到与名称匹配的bean时，再按类型装配。

(1).@Resource: JDK提供,移植性强,推荐使用, 可以看到支撑类是: import javax.annotation.Resource; 只要是JDK1.5以上版本,JDK内置了此注释支撑类.

(2).用法：

用在属性上

示例：

//dao层接口：

package com.spring.chapter5.dao;

public interface FruitDao {
	public void create();
}

//dao层实现类

package com.spring.chapter5.dao.impl;

import com.spring.chapter5.dao.FruitDao;

public class FruitDaoImpl implements FruitDao {
	public void create() {
		System.out.println("Dao层方法create被调用");
	}
}

//service层接口

package com.spring.chapter5.service;

public interface FruitService {
	public void create();
}

//service层实现类

package com.spring.chapter5.service.impl;

import javax.annotation.Resource;
import com.spring.chapter5.dao.FruitDao;
import com.spring.chapter5.service.FruitService;

public class FruitServiceImpl implements FruitService {
	@Resource
	private FruitDao fruitDao;

	public void create() {
		fruitDao.create();
	}

	public void setFruitDao(FruitDao fruitDao) {
		this.fruitDao = fruitDao;
	}
}

//配置文件(chapter5.xml)

<?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="fruitDao" class="com.spring.chapter5.dao.impl.FruitDaoImpl" />
	<bean id="fruitService" class="com.spring.chapter5.service.impl.FruitServiceImpl" />
</beans>

注意：我们只在xml中配置了两个bean对象，它们之间并没有关系，但是在Java中我们采用注释语法，这个时候@Resource注释语法会根据属性名称在spring容器中去寻找和属性名称同名id的bean对象，然后将其注入到属性中。

//测试类

package com.spring.chapter5.service.impl;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.spring.chapter5.service.FruitService;

public class Test {
	public static void main(String[] args) {
		ApplicationContext act = new ClassPathXmlApplicationContext("chapter5.xml");
		FruitService fruitService = (FruitService) act.getBean("fruitService");
		fruitService.create();
	}
}

(3).更改配置文件

将<bean id="fruitDao" class="com.spring.chapter5.dao.impl.FruitDaoImpl" />改为<bean id="myFruitDao" class="com.spring.chapter5.dao.impl.FruitDaoImpl" />

这个时候可以看到myFruitDao和属性名称并没有对应，但执行Test文件后，可以看到执行成功。这因为如果名称上没有对应，就会按类型自动对性，所以会执行成功。

(4).我们还可以给@Resource加上name,请看下面的语法

//service层实现类

public class FruitServiceImpl implements FruitService {
	@Resource(name="myFruitDao")
	private FruitDao fruitDao;

	public void create() {
		fruitDao.create();
	}

	public void setFruitDao(FruitDao fruitDao) {
		this.fruitDao = fruitDao;
	}
}

再次执行Test,同样可以执行成功.

(5).用上属性的set方法上

//service层实现类

public class FruitServiceImpl implements FruitService {	
	private FruitDao fruitDao;

	public void create() {
		fruitDao.create();
	}

	@Resource(name="myFruitDao")
	public void setFruitDao(FruitDao fruitDao) {
		this.fruitDao = fruitDao;
	}
}

可以看到,用在属性上,或者用上属性的set方法上,效果是一模一样的,没有任何区别.

三：@Autowired

//service层实现类

public class FruitServiceImpl implements FruitService {	
	private FruitDao fruitDao;

	public void create() {
		fruitDao.create();
	}

	@Autowired
	public void setFruitDao(FruitDao fruitDao) {
		this.fruitDao = fruitDao;
	}
}

运行Test文件,可以看到效果一样

同样,我们也可以把@Autowired改成按名称装配

//service层实现类

public class FruitServiceImpl implements FruitService {
	@Autowired()
	@Qualifier("myFruitDao")
	private FruitDao fruitDao;
		
	public void create() {
		fruitDao.create();
	}

	public void setFruitDao(FruitDao fruitDao) {
		this.fruitDao = fruitDao;
	}
}

这里需要注意的是:

   @Autowired()
   @Qualifier("myaFruitDao")
   private FruitDao fruitDao;
   这两句只能用在属性上,不能用上方法上.

@Autowired的required属性

   @Autowired(required=true)
   @Qualifier("myFruitDao")
   required=true : 必须为属性注入值,
   required=false: 不是必须注入值,如果找不到对应的值注入,会注入null

四：通过在classpath自动扫描方式把组件纳入到spring容器中管理.

Spring2.5引入了组件自动扫描机制,他可以在类路径下寻找标注了@Component, @Service, @Controller, @Repository注解的类, 并把这些类纳入进Spring容器中管理,它的作用,和在XML文件中使用Bean节点配置组件是一样的,要使用自动扫描机制。

<?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:component-scan base-package="com.spring.chapter5" />
</beans>

<context:component-scan base-package="com.spring.chapter5" />这一项配置了需要扫描的包,包含子包.

    @Service: 用于标注业务层的类
    @Controller: 用于标注控制层,如Action
    @Repository: 用于标注Dao层
    @Component: 用于标注组件层, 当组件不好归类的时候,可以用此标注

通过扫描机制, 基本上可以达到配置文件基本为空的效果, 这是Spring2.5新推出的功能, 老系统不能运用, 但是新系统中, 此功能运用的非常多。

示例：

//dao层实现类

package com.spring.chapter5.dao.impl;

import org.springframework.stereotype.Repository;
import com.spring.chapter5.dao.FruitDao;

@Repository
public class FruitDaoImpl implements FruitDao{	
	public void create() {
		System.out.println("Dao层方法create被调用");
	}		
}

//service层实现类

package com.spring.chapter5.service.impl;

import org.springframework.stereotype.Service;
import com.spring.chapter5.dao.FruitDao;
import com.spring.chapter5.service.FruitService;

@Service
public class FruitServiceImpl implements FruitService {
	private FruitDao fruitDao;
	
	public void create() {
		fruitDao.create();
	}
	public void setFruitDao(FruitDao fruitDao) {
		this.fruitDao = fruitDao;
	}	
}

这个时候,我将Dao层,服务层的两个实现类交给Spring管理了,相当于以前配置了两个Bean,这个时候我们可以验证一下,我们是否可以从容器中获取对象。

//xml配置

<?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:component-scan base-package="com.spring.chapter5" />
</beans>

//测试类

package com.spring.chapter5.service.impl;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.spring.chapter5.dao.FruitDao;
import com.spring.chapter5.service.FruitService;

public class Test {
	public static void main(String[] args) {
		ApplicationContext acx = new ClassPathXmlApplicationContext(
				"chapter5.xml");
		FruitDao fruitDao = (FruitDao) acx.getBean("fruitDaoImpl");
		FruitService fruitService = (FruitService) acx
				.getBean("fruitServiceImpl");
		System.out.println(fruitDao);
		System.out.println(fruitService);
	}
}

这里需要注意的是,当对象交给Spring管理后,Spring给对象起的ID名称是类的简单名称, 即类全名,但是首字母小写。

自定义名称:

//dao层实现类

package com.spring.chapter5.dao.impl;

import org.springframework.stereotype.Repository;
import com.spring.chapter5.dao.FruitDao;

@Repository("fruitDao")
public class FruitDaoImpl implements FruitDao {
	public void create() {
		System.out.println("Dao层方法create被调用");
	}
}

//service层实现类

package com.spring.chapter5.service.impl;

import org.springframework.stereotype.Service;
import com.spring.chapter5.dao.FruitDao;
import com.spring.chapter5.service.FruitService;

@Service("fruitService")
public class FruitServiceImpl implements FruitService {
	
	private FruitDao fruitDao;

	public void create() {
		fruitDao.create();
	}

	public void setFruitDao(FruitDao fruitDao) {
		this.fruitDao = fruitDao;
	}
}

//测试类

package com.spring.chapter5.service.impl;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.spring.chapter5.dao.FruitDao;
import com.spring.chapter5.service.FruitService;

public class Test {
	public static void main(String[] args) {
		ApplicationContext acx = new ClassPathXmlApplicationContext(
				"chapter2.xml");
		FruitDao fruitDao = (FruitDao)acx.getBean("fruitDao");
		FruitService fruitService = (FruitService) acx.getBean("fruitService");
		System.out.println(fruitDao);
		System.out.println(fruitService);
	}
}

五：改变对象的范围(单例或非单例)

    @Repository("fruitDao")
    @Scope("prototype")
    加上@Scope("prototype")此注释即可,这个时候每次获取对象都会是一个新对象

六：对象初始化方法和销毁方法的配置

@Repository("fruitDao")
@Scope("prototype")
public class FruitDaoImpl implements FruitDao {
	public void create() {
		System.out.println("Dao层方法create被调用");
	}
	
	@PostConstruct
	public void init(){
		System.out.println("调用init");
	}
	
	@PreDestroy
	public void destory(){
		System.out.println("调用destory");
	}
}

如果对象是非单例模式,这个时候可以看到init方法会调用两次,而destroy方法不会调用.

将Dao层注入到服务层:

@Service("fruitService")
public class FruitServiceImpl implements FruitService {
	@Resource(name="fruitDao")
	private FruitDao fruitDao;

	public void create() {
		fruitDao.create();
	}

	public void setFruitDao(FruitDao fruitDao) {
		this.fruitDao = fruitDao;
	}
}

第五章 诠释的注入

相关推荐

第五章诠释的注入