【Spring】装配Bean 组件扫描

实现自动装配需要用注解：注解分为 spring规范和java规范 ，java规范需要引入javax.inject 包 ，使用maven，直接引入。

从中可以看到 @Named @Inject属于java规范，@Component  @Autowired @Resource属于spring注解

@Named大致等效于@Component 而@Inject和@Autowired也相似，但是@Inject要强制注入，@Autowired(required=false)可以选择略过不报异常

实例：

1.写个bean接口

package test.soundsystem;

public interface CompactDisc {
  void play();
}

2.实现接口

package test.soundsystem;

import javax.inject.Named;

@Named
public class SgtPeppers implements CompactDisc {

  private String title="Sgt. Pepper's Lonely Hearts Club Band";
  private String artist = "The Beatles";
  public void play() {
    System.out.println("Playing "+title+" by "+artist);
  }
}

3.自动装配类

package test.soundsystem;

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

import test.voice.Book;

@Configuration
@ComponentScan(basePackageClasses={Book.class,CompactDisc.class})
public class CDPlayerConfig {
}

4.测试类：

package test.soundsystem;

import javax.inject.Inject;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import test.voice.Book;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=CDPlayerConfig.class)
public class CDPlayerTest {
  @Autowired
  private CompactDisc cd;
  
  @Inject
  private Book book;
  
  @Test
  public void cdShouldNotBeNull(){
    cd.play();
    book.read();
  }
}

测试结果：