spring学习笔记

为了更全面的了解spring，买了本spring实战，在这里记录自己学习的笔记

• 首先创建一个Maven工程，pom.xml如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>top.itreatment</groupId>
    <artifactId>springbootTest</artifactId>
    <version>1.0-SNAPSHOT</version>


    <dependencies>
// 这里只导入了一个核心依赖，但是Maven会根据依赖传递，加入其它核心依赖
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.1.8.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>5.1.8.RELEASE</version>
        </dependency>
    </dependencies>
</project>

• 具体导入的依赖：

  
  

• 为了演示组件扫描和自动装配，这里创建三个类：

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

@Component
public class CompartDisc {

    @Value("author")
    private String author;
    @Value("title")
    private String title;
    @Value("msg")
    private String msg;

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    @Override
    public String toString() {
        return "CompartDisc{" +
                "author='" + author + '\'' +
                ", title='" + title + '\'' +
                ", msg='" + msg + '\'' +
                '}';
    }
}

public interface MediaPlayer {

    void play();
}

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

@Component
public class CDPlayer implements MediaPlayer {

    private CompartDisc disc;

    @Autowired
    public CDPlayer(CompartDisc disc) {
        this.disc = disc;
    }

    public void play() {
        System.out.println(disc.toString());
    }
}

• 配置类：

package top.itreatment.config;

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

@Configuration
@ComponentScan(basePackages = {"top.itreatment"})
public class MyConfig {
}

• 通过组件扫描和依赖注入，上面会将CompartDisc实例加入到CDPlayer实例中，编写测试进行检验如下：

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 top.itreatment.beans.CompartDisc;
import top.itreatment.beans.MediaPlayer;
import top.itreatment.config.MyConfig;

import static org.junit.Assert.assertNotNull;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = MyConfig.class)
public class Test {

    @Autowired
    private MediaPlayer mediaPlayer;

    @Autowired
    private CompartDisc disc;

    @org.junit.Test
    public void isNull(){
        assertNotNull(disc);
        assertNotNull(mediaPlayer);
    }

    @org.junit.Test
    public void play(){
        mediaPlayer.play();
    }
}

下面将扫描方式改一下，只用显示javaConfig的方式装配bean对象：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import top.itreatment.beans.CDPlayer;
import top.itreatment.beans.CompartDisc;

@Configuration
public class MyConfig {

    @Bean
    CDPlayer cdPlayer(CompartDisc disc){
        return new CDPlayer(disc);
    }

    @Bean
    CompartDisc compartDisc(){
        CompartDisc compartDisc = new CompartDisc();
        compartDisc.setAuthor("author");
        compartDisc.setTitle("title");
        compartDisc.setMsg("msg");
        return compartDisc;
    }
}

为了将不同的业务的Bean实例在配置中分开，防止修改的时候太过于复杂。我们可以编写多个配置类，比如：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import top.itreatment.beans.CompartDisc;

@Configuration
@Import(MyConfig1.class)
public class MyConfig {

    @Bean
    CompartDisc compartDisc() {
        CompartDisc compartDisc = new CompartDisc();
        compartDisc.setAuthor("author");
        compartDisc.setTitle("title");
        compartDisc.setMsg("msg");
        return compartDisc;
    }
}

import org.springframework.context.annotation.Bean;
import top.itreatment.beans.CDPlayer;
import top.itreatment.beans.CompartDisc;

public class MyConfig1 {
    @Bean
    CDPlayer cdPlayer(CompartDisc disc) {
        return new CDPlayer(disc);
    }
}

只需要一个Import将其他的配置类导入进来就可以。不需要在其他的配置类上标Configuration注解

• 下面用xml配置文件的形式实现上面的 JavaConfig

<?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:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="http://www.springframework.org/schema/beans 
http://www.springframework.org/schema/beans/spring-beans.xsd 
http://www.springframework.org/schema/util https://www.springframework.org/schema/util/spring-util.xsd">


    <bean class="top.itreatment.beans.CDPlayer" id="cdPlayer"/>
    <bean class="top.itreatment.beans.CompartDisc" id="disc">
        <property name="author" value="作者"/>
        <property name="title" value="标题"/>
        <property name="msg" value="信息"/>
    </bean>
</beans>

• 然后将配置JavaConfig也要进行一点修改：

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

@Configuration
@ImportResource("classpath:application.xml")
public class MyConfig {

}

高级装配