Spring注解管理bean

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Spring针对Bean管理中创建对象提供注解

(1) @Component

(2) @Service

(3) @Controller

(4)@Repository

上面的4个注解功能是一样的，都可以用来创建bean的实例

• 第一步引入依赖

  spring-aop.jar

• 开启组件扫描

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans"
         xmlns:context="http://www.springframework.org/schema/context"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         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">
      <!--  开启组件扫描  -->
      <context:component-scan base-package="com.company.user"></context:component-scan>
  </beans>
  

  测试：

  package com.company.user;
  
  import org.springframework.stereotype.Component;
  
  @Component(value = "user")
  public class User {
      private String name;
      private int age;
  
      public User() {
      }
  
      public void setName(String name) {
          this.name = name;
      }
  
      public void setAge(int age) {
          this.age = age;
      }
  
      @Override
      public String toString() {
          return "User{" +
                  "name='" + name + '\'' +
                  ", age=" + age +
                  '}';
      }
  
      public void show() {
          System.out.println("add.....");
      }
  }
  

  package com.company.test;
  
  import com.company.user.User;
  import org.junit.Test;
  import org.springframework.context.ApplicationContext;
  import org.springframework.context.support.ClassPathXmlApplicationContext;
  
  public class SpringTest {
  
  
      @Test
      public void test() {
          ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
          User user = context.getBean("user", User.class);
          System.out.println(user);
          user.show();
      }
  
  }
  

  • 组件扫描细节配置

    <context:component-scan base-package="com.company.user" use-default-filters="false">
        <context:include-filter type="annotation" expression="org.springframework.stereotype.Component"/>
    </context:component-scan>
    

• 基于注解方式实现属性注解

  @AutoWired 根据属性类型自动装配

  1. 把service和dao对象创建，在service和dao类添加创建对象注解
  2. 在service注入dao对象，在service类添加dao类型属性，在属性上面使用注解

  @Qualifier 根据属性名称注入

  这个@Qualifier注解需要跟！@AutoWired一起使用

package com.company.dao;
 
import org.springframework.stereotype.Repository;
 
@Repository(value = "userDaoImpl")
 public class UserDaoImpl implements UserDao{
     @Override
     public void add() {
         System.out.println("dao add。。。");
     }
 }

package com.company.service;

import com.company.dao.UserDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;

@Service
public class UserService {


    @Autowired
    @Qualifier(value = "userDaoImpl")
    private UserDao userDao;

    public void add() {
        System.out.println("service add....");
        userDao.add();
    }

}

@Resource 可以根据类型，可以根据名称

package com.company.service;

import com.company.dao.UserDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;

@Service
public class UserService {


//    @Autowired
//    @Qualifier(value = "userDaoImpl")
//    private UserDao userDao;

    @Resource(name = "userDaoImpl")
    private UserDao userDao;

    public void add() {
        System.out.println("service add....");
        userDao.add();
    }

}

@Value

@Value(value = "abc")
private String name;

完全注解来发

1. 创建配置类，替代xml配置文件

package com.company.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan(basePackages = "com.company")
public class SpringConfig {



}

@Test
public void test3() {
    ApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
    UserService userService = context.getBean("userService", UserService.class);
    userService.add();
}