Spring-组件扫描

spring会自动发现应用上下文中所创建的bean。

创建一个CDPleaer类，让Spring发现它，并将CompactDisc bean注入进来。

SgtPeppers.java
主要是用@Component注解，表明该类会作为一个组件类。

package soundsystem;
import org.springframework.stereotype.Component;

@Component
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);
  }
  
}

不过组件扫描默认是不启用的，得配置一下Spring，让他去寻找带有@Component的组件，如下:
CDPlayerConfig.java

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

@Configuration
@ComponentScan
public class CDPlayerConfig { 
}

然后通过CDPlayerTest.java类来测试。

package soundsystem;

import static org.junit.Assert.*;

import org.junit.Rule;
import org.junit.Test;
import org.junit.contrib.java.lang.system.StandardOutputStreamLog;
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;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=CDPlayerConfig.class)
public class CDPlayerTest {


  
  @Autowired
  private CompactDisc cd;
  
  @Test
  public void cdShouldNotBeNull() {
    assertNotNull(cd);
  }


}

:compileJava UP-TO-DATE
:processResources UP-TO-DATE
:classes UP-TO-DATE
:compileTestJava
:processTestResources UP-TO-DATE
:testClasses
:test

BUILD SUCCESSFUL

Total time: 16.894 secs

gradle测试通过，说明SgtPeppers被很好的创建出来了,不为空。