Spring in action读书笔记（一） 自动化装配bean

需要引入的ja包

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.1.9.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>5.1.9.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>

1、自动注入属性

定义CD播放器对CD所能进行的操作接口类

package test.aop;

public interface CompactDisc {
    void play();
}

定义CompactDisc接口的实现类SgtPeppers，增加component注解，将SgtPeppers类作为组件类

package test.aop;

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);
    }
}

Spring中组件扫描默认是不启用的，需要显示配置Spring，让其去寻找带有@Component注解的类， @ComponentScan在没有显示指定参数情况会默认扫描与配置类相同的包test.aop，

即Spring会扫描这个包以及这个包下的所有子包，查找带有@Component注解的类。这样就能发现CompactDisc接口及其实现类，并为其创建一个bean。

package test.aop;

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

@Configuration
@ComponentScan
public class CDPlayerConfig {

}

测试扫描组件能够发现CompactDisc

package test.aop;

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 static junit.framework.TestCase.assertNotNull;

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

    @Autowired
    private CompactDisc cd;

    @Test
    public void dcShouldNotBeNull() {
        assertNotNull(cd);
    }

}

2、 自动注入方法

创建MediaPlayer接口及其实现类CDPlayer，实现类CDPlayer需要注入CompactDisc

package test.aop;

public interface MediaPlayer {

    void play();
}

package test.aop;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class CDPlayer implements MediaPlayer {

    private CompactDisc cd;

    @Autowired
    public CDPlayer(CompactDisc cd) {
        this.cd = cd;
    }

    public void play() {
        cd.play();
    }
}

测试类

package test.aop;

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;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

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

    @Rule
    public final StandardOutputStreamLog log = new StandardOutputStreamLog();

    @Autowired
    private CompactDisc cd;

    @Autowired
    private MediaPlayer player;

    @Test
    public void dcShouldNotBeNull() {
        assertNotNull(cd);
    }

    @Test
    public void player() {
        player.play();
        assertEquals("PlayingSgt. Pepper's Lonely Hearts Club Band by The Beatles\r\n", log.getLog());
    }

}

需要引入jar包

        <!-- https://mvnrepository.com/artifact/com.github.stefanbirkner/system-rules -->
        <dependency>
            <groupId>com.github.stefanbirkner</groupId>
            <artifactId>system-rules</artifactId>
            <version>1.16.0</version>
        </dependency>