Bean的配置方式

基于XML文件的方式
基于注解的方式（基于注解配置Bean，基于注解来装配Bean的属性）

在classpath中扫描组件

组件扫描：Spring能够从classpath下自动扫描、侦测和实例化具有特定注解的组件
特定组件包括：
- @component：基本注解，标识了一个受Spring管理的组件
- @Respositoy：标识持久层组件
- @Service：标识服务层组件
- @Controller：标识表现层组件
对于扫描到的组件，Spring有默认的命名规则，使用非限定类名，第一个字母小写，也可以在注解中通过value属性标识组件的名称

当在组件类中使用了特定的注解后，还需要在Spring的配置文件中声明<context:component-scan>：

TestObject.java

package com.glemontree.spring.annotation;
import org.springframework.stereotype.Component;
@Component
public class TestObject {
}

UserController.java

package com.glemontree.spring.annotation.controller;
import org.springframework.stereotype.Controller;
@Controller
public class UserController {
	public void execute() {
		System.out.println("UserController execute...");
	}
}

UserRepository.java UserRepositoryImpl.java

package com.glemontree.spring.annotation.repository;
public interface UserRepository {
	void save();
}

package com.glemontree.spring.annotation.repository;
import org.springframework.stereotype.Repository;
@Repository("userRepository")
public class UserRepositoryImpl implements UserRepository {
	public void save() {
		// TODO Auto-generated method stub
		System.out.println("UserRepository Save...");
	}
}

UserService.java

package com.glemontree.spring.annotation.sevice;
import org.springframework.stereotype.Service;
@Service
public class UserService {
	public void add() {
		System.out.println("UserService add...");
	}
}

配置文件：

<?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:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
  	<!--扫描com.glemontree.spring.annotation包及其子包-->
	<context:component-scan base-package="com.glemontree.spring.annotation">
	</context:component-scan>
</beans>

测试方法

package com.glemontree.spring.annotation;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.glemontree.spring.annotation.controller.UserController;
import com.glemontree.spring.annotation.repository.UserRepository;
import com.glemontree.spring.annotation.sevice.UserService;
public class Main {
	public static void main(String[] args) {
		ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-annotation.xml");
		TestObject to = (TestObject) ctx.getBean("testObject");
		System.out.println(to);
		
		UserController uc = (UserController) ctx.getBean("userController");
		System.out.println(uc);
		
		UserService us = (UserService) ctx.getBean("userService");
		System.out.println(us);
		
		UserRepository ur = (UserRepository) ctx.getBean("userRepository");
		System.out.println(ur);
	}
}

解析：

base-package：指定一个需要扫描的基类包，Spring将会扫描这个基类包里极其子包里的所有类
当需要扫描多个包时，可以使用逗号分隔

如果仅希望扫描特定的类而非基包下的所有类，可使用resource-pattern属性过滤特定的类：

<!--可以通过resource-pattern指定扫描的资源-->
<context:component-scan
                        base-package="com.glemontree.spring.beans"
                        resource-pattern:"autowire/*.class"/>

<context:include-filter>子结点表示包含哪些指定表达式的组件，该子结点需要use-default-filter配合使用，即设置<context:component-scan>的use-default-filter属性为false；

<?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.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
	<context:component-scan 
		base-package="com.glemontree.spring.annotation"
		use-default-filters="false">
		<context:include-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
	</context:component-scan>
</beans>

<context:exclude-filter>子结点表示排除哪些指定表达式的组件；

<?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:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
	<context:component-scan 
		base-package="com.glemontree.spring.annotation">
      	<!--不包含标注了@Repository的类-->
		<context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
	</context:component-scan>
</beans>

<context:component-scan>下可以包含多个<context:include-filter>和<context:exclude-filter>子结点

<context:include-filter>和<context:exclude-filter>子结点支持多种类型的过滤表达式，常用的有：

annotation：所有标注了xxxAnnotation的类

<?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.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
	<context:component-scan 
		base-package="com.glemontree.spring.annotation">
      	<!--不包含标注了@Repository的类-->
		<context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
	</context:component-scan>
</beans>

assinable：所有继承或扩展xxxService的类

<?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.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
	<!-- <context:component-scan 
		base-package="com.glemontree.spring.annotation"
		use-default-filters="false">
		<context:include-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
	</context:component-scan> -->
	<context:component-scan 
		base-package="com.glemontree.spring.annotation"
		use-default-filters="true">
      	<!--排除所有UserRepository和继承自UserRepository的类-->
		<context:exclude-filter type="assignable" expression="com.glemontree.spring.annotation.repository.UserRepository"/>
	</context:component-scan>
</beans>

<?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.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
	<!-- <context:component-scan 
		base-package="com.glemontree.spring.annotation"
		use-default-filters="false">
		<context:include-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
	</context:component-scan> -->
	<context:component-scan 
		base-package="com.glemontree.spring.annotation"
		use-default-filters="false">
		<context:include-filter type="assignable" expression="com.glemontree.spring.annotation.repository.UserRepository"/>
	</context:component-scan>
</beans>

组件装配

<context:component-scan>元素还会自动注册AutowiredAnnotationBeanPostProcessor实例，该实例可以自动装配具有@Autowired和@Resource、@Inject注解的属性。

Autowired：可以自动装配具有兼容类型的单个Bean属性

构造器、普通字段（即使是非public）以及一切具有参数的方法都可以应用@Autowired注解
默认情况下，所有使用@Autowired注解的属性都要被设置，当Spring找不到匹配的Bean装配属性时，会抛出异常，若某一属性允许不被设置，可以设置@Autowired注解的required属性为false

默认情况下，当IOC容器里存在多个类型兼容Bean时，通过类型的自动装配将无法工作，此时可以在@Qualifier注解里提供Bean的名称，Spring允许对方法的入参标注@Qualifier以指定注入Bean的名称：

package com.glemontree.spring.annotation.sevice;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
import com.glemontree.spring.annotation.repository.UserRepository;
@Service
public class UserService {
	
	private UserRepository userRepository;
	
	@Autowired
	@Qualifier("userRepositoryImpl") // 通过@Qualifier指定Bean的名称，注意是bean的名称而不是类的名称
	public void setUserRepository(UserRepository userRepository) {
		this.userRepository = userRepository;
	}
	public void add() {
		System.out.println("UserService add...");
		userRepository.save();
	}
}

另外一种写法如下：

package com.glemontree.spring.annotation.sevice;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
import com.glemontree.spring.annotation.repository.UserRepository;
@Service
public class UserService {
	
	private UserRepository userRepository;
	
  	// 将@Qualifier写在入参的前面
	@Autowired
	public void setUserRepository(@Qualifier("userRepositoryImpl")UserRepository userRepository) {
		this.userRepository = userRepository;
	}
	public void add() {
		System.out.println("UserService add...");
		userRepository.save();
	}
}

泛型依赖注入

BaseRepository.java

package com.glemontree.spring.generic.di;
public class BaseRepository<T> {
}

BaseService.java

package com.glemontree.spring.generic.di;
import org.springframework.beans.factory.annotation.Autowired;
public class BaseService<T> {
  	// BaseService依赖于BaseRepository，通过@Autowired建立关系
	@Autowired
	protected BaseRepository<T> repository;
	public void add() {
		System.out.println("add...");
		System.out.println(repository);
	}
}

User.java

package com.glemontree.spring.generic.di;
public class User {
}

UserRepositpry.java

package com.glemontree.spring.generic.di;
import org.springframework.stereotype.Repository;
// 通过@Repository注解注册bean
@Repository
public class UserRepository extends BaseRepository<User>{
}

UserService.java

package com.glemontree.spring.generic.di;
import org.springframework.stereotype.Service;
// 通过@Service注解注册bean
@Service
public class UserService extends BaseService<User>{
	
}

beans-generic-di.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.xsd
                           http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
// 通过下面这段话UserRepository和UserService两个bean会被注册
<context:component-scan base-package="com.glemontree.spring.generic.di"></context:component-scan>
</beans>

虽然UserService和UserRepository之间并没有建立直接的联系，但是两个泛型类BaseService<T>和BaseRepository<T>之间通过@Autowired建立了联系，因此它们的两个子类UserService和UserRepository也建立了联系。

[Spring] 基于注解来配置Bean

2017-06-28
Spring

[Spring] 基于注解来配置Bean

Bean的配置方式

在classpath中扫描组件

组件装配

泛型依赖注入

[Spring] 基于注解来配置Bean

Bean的配置方式

在classpath中扫描组件

组件装配

泛型依赖注入

谢谢打赏