在 classpath 中扫描组件
•组件扫描(component scanning): 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
–@Respository: 标识持久层组件
–@Service: 标识服务层(业务层)组件
–@Controller: 标识表现层组件
•对于扫描到的组件, Spring 有默认的命名策略: 使用非限定类名, 第一个字母小写. 也可以在注解中通过 value 属性值标识组件的名称
•当在组件类上使用了特定的注解之后, 还需要在 Spring 的配置文件中声明 <context:component-scan> :
–base-package 属性指定一个需要扫描的基类包,Spring 容器将会扫描这个基类包里及其子包中的所有类.
–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,示例:
–
–
–
–<context:include-filter> 子节点表示要包含的目标类
–<context:exclude-filter> 子节点表示要排除在外的目标类
–<context:component-scan> 下可以拥有若干个 <context:include-filter> 和 <context:exclude-filter> 子节点
•<context:include-filter> 和 <context:exclude-filter> 子节点支持多种类型的过滤表达式:
testObject.java
package com.hzyc.spring.bean.annotation;
import org.springframework.stereotype.Component;
/**
* @author xuehj2016
* @Title: TestObject
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:30
*/
@Component
public class TestObject {
}
userController.java
package com.hzyc.spring.bean.annotation.controller;
import org.springframework.stereotype.Controller;
/**
* @author xuehj2016
* @Title: UserController
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:39
*/
@Controller
public class UserController {
public void execute(){
System.out.println("UserController Execute...");
}
}
userRepository.java
package com.hzyc.spring.bean.annotation.repository;
/**
* @author xuehj2016
* @Title: UserRepository
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:34
*/
public interface UserRepository {
void save();
}
userRepositoryImpl.java
package com.hzyc.spring.bean.annotation.repository;
import org.springframework.stereotype.Repository;
/**
* @author xuehj2016
* @Title: UserRepositoryImpl
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:35
*/
@Repository("userRepository")
public class UserRepositoryImpl implements UserRepository {
@Override
public void save() {
System.out.println("UserRepository Save...");
}
}
userService.java
package com.hzyc.spring.bean.annotation.service;
import org.springframework.stereotype.Service;
/**
* @author xuehj2016
* @Title: UserService
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:37
*/
@Service
public class UserService {
public void add() {
System.out.println("UserService Add...");
}
}
bean-annotation.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.xsd">
<!--指定 Spring IOC 容器扫描的包-->
<!--可以通过 resource-pattern 指定扫描的资源-->
<!--
<context:component-scan
base-package="com.hzyc.spring.bean.annotation"
resource-pattern="repository/*.class"/>
-->
<!--context:exclude-filter : 子节点指定排除哪些指定表达式的组件-->
<!--context:include-filter : 子节点指定包含哪些表达式的组件,该节点需要 use-default-filters="false" 配合使用-->
<!---->
<context:component-scan
base-package="com.hzyc.spring.bean.annotation"
use-default-filters="false">
<!--
<context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
-->
<!--
<context:include-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
-->
<!--
<context:exclude-filter type="assignable"
expression="com.hzyc.spring.bean.annotation.repository.UserRepository"/>
-->
<context:include-filter type="assignable"
expression="com.hzyc.spring.bean.annotation.repository.UserRepository"/>
</context:component-scan>
</beans>
Main.java
package com.hzyc.spring.bean.annotation;
import com.hzyc.spring.bean.annotation.controller.UserController;
import com.hzyc.spring.bean.annotation.repository.UserRepository;
import com.hzyc.spring.bean.annotation.repository.UserRepositoryImpl;
import com.hzyc.spring.bean.annotation.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
/**
* @author xuehj2016
* @Title: Main
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:44
*/
public class Main {
public static void main(String[] args) {
ApplicationContext applicationContext=new ClassPathXmlApplicationContext("bean-annotation.xml");
TestObject testObject= (TestObject) applicationContext.getBean("testObject");
System.out.println(testObject);
UserController userController= (UserController) applicationContext.getBean("userController");
System.out.println(userController);
UserService userService= (UserService) applicationContext.getBean("userService");
System.out.println(userService);
UserRepositoryImpl userRepository= (UserRepositoryImpl) applicationContext.getBean("userRepository");
System.out.println(userRepository);
}
}
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.
使用 @Autowired 自动装配 Bean
•@Autowired 注解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), 一切具有参数的方法都可以应用@Authwired 注解
–默认情况下, 所有使用 @Authwired 注解的属性都需要被设置. 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 @Authwired 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的 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 @Qualifiter 已指定注入 Bean 的名称
– @Authwired 注解也可以应用在数组类型的属性上, 此时 Spring 将会把所有匹配的 Bean 进行自动装配.
–@Authwired 注解也可以应用在集合属性上, 此时 Spring 读取该集合的类型信息, 然后自动装配所有与之兼容的 Bean.
–@Authwired 注解用在 java.util.Map 上时, 若该 Map 的键值为 String, 那么 Spring 将自动装配与之 Map 值类型兼容的 Bean, 此时 Bean 的名称作为键值
•
使用 @Resource 或 @Inject
自动装配 Bean
•Spring 还支持 @Resource 和 @Inject 注解,这两个注解和 @Autowired 注解的功用类似
•@Resource 注解要求提供一个 Bean 名称的属性,若该属性为空,则自动采用标注处的变量或方法名作为 Bean 的名称
•@Inject 和 @Autowired 注解一样也是按类型匹配注入的 Bean, 但没有 reqired 属性
•建议使用 @Autowired 注解
testObject.java
package com.hzyc.spring.bean.annotation;
import org.springframework.stereotype.Component;
/**
* @author xuehj2016
* @Title: TestObject
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:30
*/
@Component
public class TestObject {
}
userController.java
package com.hzyc.spring.bean.annotation.controller;
import com.hzyc.spring.bean.annotation.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
/**
* @author xuehj2016
* @Title: UserController
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:39
*/
@Controller
public class UserController {
@Autowired
private UserService userService;
public void execute() {
System.out.println("UserController Execute...");
userService.add();
}
}
userRepository.java
package com.hzyc.spring.bean.annotation.repository;
/**
* @author xuehj2016
* @Title: UserRepository
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:34
*/
public interface UserRepository {
void save();
}
userRepositoryImpl.java
package com.hzyc.spring.bean.annotation.repository;
import com.hzyc.spring.bean.annotation.TestObject;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
/**
* @author xuehj2016
* @Title: UserRepositoryImpl
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:35
*/
@Repository
/*("userRepository")*/
public class UserRepositoryImpl implements UserRepository {
@Autowired(required = false)
private TestObject testObject;
@Override
public void save() {
System.out.println("UserRepository Save...");
System.out.println(testObject);
}
}
userService.java
package com.hzyc.spring.bean.annotation.service;
import com.hzyc.spring.bean.annotation.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
/**
* @author xuehj2016
* @Title: UserService
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:37
*/
@Service
public class UserService {
@Autowired
@Qualifier("userRepositoryImpl")
private UserRepository userRepository;
public void add() {
System.out.println("UserService Add...");
userRepository.save();
}
@Autowired
public void setUserRepository(@Qualifier("userRepositoryImpl")
UserRepository userRepository) {
this.userRepository = userRepository;
}
}
UserJdbcRepository.java
package com.hzyc.spring.bean.annotation.repository;
import org.springframework.stereotype.Repository;
/**
* @author xuehj2016
* @Title: UserJdbcRepository
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 22:45
*/
@Repository
public class UserJdbcRepository implements UserRepository {
@Override
public void save() {
System.out.println("UserJdbcRepository save...");
}
}
bean-annotation.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.xsd">
<!--指定 Spring IOC 容器扫描的包-->
<!--可以通过 resource-pattern 指定扫描的资源-->
<!--
<context:component-scan
base-package="com.hzyc.spring.bean.annotation"
resource-pattern="repository/*.class"/>
-->
<!--context:exclude-filter : 子节点指定排除哪些指定表达式的组件-->
<!--context:include-filter : 子节点指定包含哪些表达式的组件,该节点需要 use-default-filters="false" 配合使用-->
<!---->
<context:component-scan
base-package="com.hzyc.spring.bean.annotation">
<!--
<context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
-->
<!--
<context:include-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
-->
<!--
<context:exclude-filter type="assignable"
expression="com.hzyc.spring.bean.annotation.repository.UserRepository"/>
-->
<!--
<context:include-filter type="assignable"
expression="com.hzyc.spring.bean.annotation.repository.UserRepository"/>
-->
</context:component-scan>
</beans>
Main.java
package com.hzyc.spring.bean.annotation;
import com.hzyc.spring.bean.annotation.controller.UserController;
import com.hzyc.spring.bean.annotation.repository.UserRepository;
import com.hzyc.spring.bean.annotation.repository.UserRepositoryImpl;
import com.hzyc.spring.bean.annotation.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
/**
* @author xuehj2016
* @Title: Main
* @ProjectName Spring
* @Description: TODO
* @date 2018/12/18 20:44
*/
public class Main {
public static void main(String[] args) {
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean-annotation.xml");
// TestObject testObject= (TestObject) applicationContext.getBean("testObject");
// System.out.println(testObject);
UserController userController = (UserController) applicationContext.getBean("userController");
System.out.println(userController);
userController.execute();
//
// UserService userService= (UserService) applicationContext.getBean("userService");
// System.out.println(userService);
//
// UserRepositoryImpl userRepository= (UserRepositoryImpl) applicationContext.getBean("userRepository");
// System.out.println(userRepository);
}
}