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spring装配bean的三种方式及其混合装配

在spring容器中装配bean有三种基本方式和混合装配方式：

隐式的bean自动发现机制和自动装配
在java中进行显式配置
在xml中配置
混合装配（在多个java文件中配置、在JavaConfig中引用XML配置、在XML中引用JavaConfig配置）

一、使用自动化方式装配bean示例：

1:创建maven项目并引入依赖：

<?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>com.springinaction.cn</groupId>
  <artifactId>BeanWiring</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>BeanWiring</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-aop</artifactId>
      <version>4.3.1.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>4.3.1.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>4.3.1.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-test</artifactId>
      <version>4.3.5.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-jdbc</artifactId>
      <version>4.3.5.RELEASE</version>
    </dependency>
  </dependencies>

  <build>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-jar-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
        <plugin>
          <artifactId>maven-site-plugin</artifactId>
          <version>3.7.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-project-info-reports-plugin</artifactId>
          <version>3.0.0</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

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2:创建简单java类接口及其实现，并将其实现类增加@Component注解，spring容器将为这个类创建bean：

package com.springinaction.cn;

public interface CompactDisc {
    public void play();
}

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package com.springinaction.cn;

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);
    }
}

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3:创建配置类，启用组件扫描：

package com.springinaction.cn;

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

@Configuration
@ComponentScan
public class CDPlayerConfig {
}

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至此，可被被spring自动装配的bean已经创建好了，用junit测试一下：

package com.springinaction.cn;

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;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = CDPlayerConfig.class)
public class CDPlayerTest {
    @Autowired
    private CompactDisc cd;

    @Test
    public void cdShouldNotBeNull(){
        cd.play();
    }

}

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运行结果：

/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/bin/java -ea -Didea.test.cyclic.buffer.size=10485760 "-javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=60362:/Applications/IntelliJ IDEA.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath "/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar:/Applications/IntelliJ IDEA.app/Contents/plugins/junit/lib/junit-rt.jar:/Applications/IntelliJ IDEA.app/Contents/plugins/junit/lib/junit5-rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/tools.jar:/Users/zhenghongbo/IdeaProjects/BeanWiring/target/test-classes:/Users/zhenghongbo/IdeaProjects/BeanWiring/target/classes:/Users/zhenghongbo/Documents/apache-maven-local-repo/junit/junit/4.12/junit-4.12.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-aop/4.3.1.RELEASE/spring-aop-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-beans/4.3.1.RELEASE/spring-beans-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-core/4.3.1.RELEASE/spring-core-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/commons-logging/commons-logging/1.2/commons-logging-1.2.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-context/4.3.1.RELEASE/spring-context-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-expression/4.3.1.RELEASE/spring-expression-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-test/4.3.5.RELEASE/spring-test-4.3.5.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-jdbc/4.3.5.RELEASE/spring-jdbc-4.3.5.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-tx/4.3.5.RELEASE/spring-tx-4.3.5.RELEASE.jar" com.intellij.rt.execution.junit.JUnitStarter -ideVersion5 -junit4 com.springinaction.cn.CDPlayerTest,cdShouldNotBeNull
Jun 19, 2019 9:35:10 PM org.springframework.test.context.support.DefaultTestContextBootstrapper getDefaultTestExecutionListenerClassNames
INFO: Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
Jun 19, 2019 9:35:10 PM org.springframework.test.context.support.DefaultTestContextBootstrapper instantiateListeners
INFO: Could not instantiate TestExecutionListener [org.springframework.test.context.web.ServletTestExecutionListener]. Specify custom listener classes or make the default listener classes (and their required dependencies) available. Offending class: [javax/servlet/ServletContext]
Jun 19, 2019 9:35:10 PM org.springframework.test.context.support.DefaultTestContextBootstrapper getTestExecutionListeners
INFO: Using TestExecutionListeners: [org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@2d6e8792, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@2812cbfa, org.springframework.test.context.support.DirtiesContextTestExecutionListener@2acf57e3, org.springframework.test.context.transaction.TransactionalTestExecutionListener@506e6d5e, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@96532d6]
Jun 19, 2019 9:35:10 PM org.springframework.context.support.GenericApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.GenericApplicationContext@4590c9c3: startup date [Wed Jun 19 21:35:10 CST 2019]; root of context hierarchy
Playing sgt. pepper's lonely hearts club band by the beatles
Jun 19, 2019 9:35:10 PM org.springframework.context.support.GenericApplicationContext doClose
INFO: Closing org.springframework.context.support.GenericApplicationContext@4590c9c3: startup date [Wed Jun 19 21:35:10 CST 2019]; root of context hierarchy

Process finished with exit code 0

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4:接下来通过给bean添加注解来实现自动装配：

再创建一个bean，这个bean需要用到上面创建的compactDisc类（依赖这个类）：

package com.springinaction.cn;

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

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

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

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再次测试一下：

package com.springinaction.cn;

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;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = CDPlayerConfig.class)
public class CDPlayerTest {
    @Autowired
    private CompactDisc cd;

    @Test
    public void cdShouldNotBeNull(){
        cd.play();
    }

    @Autowired
    private CDPlayer player;
    @Test
    public void play(){
        player.play();
    }

}

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测试结果：

/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/bin/java -ea -Didea.test.cyclic.buffer.size=10485760 "-javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=64301:/Applications/IntelliJ IDEA.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath "/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar:/Applications/IntelliJ IDEA.app/Contents/plugins/junit/lib/junit-rt.jar:/Applications/IntelliJ IDEA.app/Contents/plugins/junit/lib/junit5-rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/tools.jar:/Users/zhenghongbo/IdeaProjects/BeanWiring/target/test-classes:/Users/zhenghongbo/IdeaProjects/BeanWiring/target/classes:/Users/zhenghongbo/Documents/apache-maven-local-repo/junit/junit/4.12/junit-4.12.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-aop/4.3.1.RELEASE/spring-aop-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-beans/4.3.1.RELEASE/spring-beans-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-core/4.3.1.RELEASE/spring-core-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/commons-logging/commons-logging/1.2/commons-logging-1.2.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-context/4.3.1.RELEASE/spring-context-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-expression/4.3.1.RELEASE/spring-expression-4.3.1.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-test/4.3.5.RELEASE/spring-test-4.3.5.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-jdbc/4.3.5.RELEASE/spring-jdbc-4.3.5.RELEASE.jar:/Users/zhenghongbo/Documents/apache-maven-local-repo/org/springframework/spring-tx/4.3.5.RELEASE/spring-tx-4.3.5.RELEASE.jar" com.intellij.rt.execution.junit.JUnitStarter -ideVersion5 -junit4 com.springinaction.cn.CDPlayerTest,play
Jun 19, 2019 10:02:30 PM org.springframework.test.context.support.DefaultTestContextBootstrapper getDefaultTestExecutionListenerClassNames
INFO: Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
Jun 19, 2019 10:02:30 PM org.springframework.test.context.support.DefaultTestContextBootstrapper instantiateListeners
INFO: Could not instantiate TestExecutionListener [org.springframework.test.context.web.ServletTestExecutionListener]. Specify custom listener classes or make the default listener classes (and their required dependencies) available. Offending class: [javax/servlet/ServletContext]
Jun 19, 2019 10:02:30 PM org.springframework.test.context.support.DefaultTestContextBootstrapper getTestExecutionListeners
INFO: Using TestExecutionListeners: [org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@2812cbfa, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@2acf57e3, org.springframework.test.context.support.DirtiesContextTestExecutionListener@506e6d5e, org.springframework.test.context.transaction.TransactionalTestExecutionListener@96532d6, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@3796751b]
Jun 19, 2019 10:02:30 PM org.springframework.context.support.GenericApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.GenericApplicationContext@32e6e9c3: startup date [Wed Jun 19 22:02:30 CST 2019]; root of context hierarchy
Playing sgt. pepper's lonely hearts club band by the beatles

Process finished with exit code 0

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代码结构：

注解总结：

@Component 使用在类上，表示该类是一个组件类，spring容器将为这个类创建bean，@Component注解常用的属性是设置bean的id：@Component("lonelyHeartsClub")，可以使用@Named注解代替@Component注解；

@Configuration表明该类是一个配置类（用来代替spring的xml形式的配置文件）；

@ComponentScan该注解用于在spring中启用组件扫描，该注解最常用的属性是basePackages，例如：@ComponentScan（basePackages={"soundsystem", "video"}）这种方式指定扫描基础包，另一种类型安全的指定基础扫描包的方式是使用basePackagesClasses，例如@ComponentScan（basePackagesClasses={CDPlayer.class, DVDPlayer.class}）,这些类所在的包将成为扫描的基础包；

@Autowired注解用于实现自动装配，spring将在应用上下文中查找需要注入的bean，@Autowired注解可以用在类的任何方法上（构造器、Setter）或者是用在属性上；@Autowired是spring的注解，可以用@Inject注解代替；

二、使用java代码显式装配bean：

既然是使用显式配置，则需要将上面的代码中的组件扫描注解移除掉：

package com.springinaction.cn;

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

@Configuration
public class CDPlayerConfig {
}

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这时候如果再次运行测试，会直接失败：

SEVERE: Caught exception while allowing TestExecutionListener [org.springframework.test.context.support.DependencyInjectionTestExecutionListener@2acf57e3] to prepare test instance [com.springinaction.cn.CDPlayerTest@7c0c77c7]
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'com.springinaction.cn.CDPlayerTest': Unsatisfied dependency expressed through field 'cd': No qualifying bean of type [com.springinaction.cn.CompactDisc] found for dependency [com.springinaction.cn.CompactDisc]: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.springinaction.cn.CompactDisc] found for dependency [com.springinaction.cn.CompactDisc]: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:569)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
。。。

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此时需要在JavaConfig中显示声明Bean并组装Bean：

package com.springinaction.cn;

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

@Configuration
public class CDPlayerConfig {

    @Bean(name = "lonelyHeartsClubBand")
    public CompactDisc sgtPeppers(){
        return new SgtPeppers();
    }

    @Bean
    public CDPlayer cdPlayer(CompactDisc compactDisc){
        return new CDPlayer(compactDisc);
    }
}

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再次运行测试程序，测试通过：

INFO: Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
Jun 19, 2019 10:42:32 PM org.springframework.test.context.support.DefaultTestContextBootstrapper instantiateListeners
INFO: Could not instantiate TestExecutionListener [org.springframework.test.context.web.ServletTestExecutionListener]. Specify custom listener classes or make the default listener classes (and their required dependencies) available. Offending class: [javax/servlet/ServletContext]
Jun 19, 2019 10:42:32 PM org.springframework.test.context.support.DefaultTestContextBootstrapper getTestExecutionListeners
INFO: Using TestExecutionListeners: [org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@2812cbfa, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@2acf57e3, org.springframework.test.context.support.DirtiesContextTestExecutionListener@506e6d5e, org.springframework.test.context.transaction.TransactionalTestExecutionListener@96532d6, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@3796751b]
Jun 19, 2019 10:42:32 PM org.springframework.context.support.GenericApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.GenericApplicationContext@32e6e9c3: startup date [Wed Jun 19 22:42:32 CST 2019]; root of context hierarchy
Playing sgt. pepper's lonely hearts club band by the beatles

Process finished with exit code 0

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注解总结：

@Bean注解：带有Bean注解的方法用于产生Bean的实例，@Bean注解可使用name属性指定别名。与@Bean注解配合使用的注解包括@Scope注解（singleton单例模式（spring默认），prototype多例，request、session、global session作用域）

三、使用XML装配Bean

（一）使用构造器注入

1:在xml中声明一个Bean：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       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">

    <bean id="compactDisc" class="com.springinaction.cn.SgtPeppers"/>
    
</beans>

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与JavaConfig不同的是，使用XML声明Bean不需要显式创建SgtPeppers的实例了，spirng发现这个Bean元素时，会调用SgtPeppers的默认构造函数来创建Bean。另外注意，Bean的类型声明是放在字符串中的，这是类型不安全的，无法在编译期的类型检查过程中发现字符串拼写错误。

2:将SgtPeppers注入到CDPlayer中(注入初始化Bean)：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       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">

    <bean id="compactDisc" class="com.springinaction.cn.SgtPeppers"/>

    <bean id="cdPlayer" class="com.springinaction.cn.CDPlayer" c:cd-ref="compactDisc"/>

</beans>

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上面的代码中使用了c命名空间来声明构造器参数。

DI依赖注入除了类之间的装配，还有需要将基本的字面值来配置对象（将字面量注入到构造器中），示例如下：

创建一个新的类BlankDisc，这个类有个构造函数接受两个字面量：

package com.springinaction.cn;

public class BlankDisc implements CompactDisc {
    private String title;
    private String artist;
    public BlankDisc(String title, String artist){
        this.title = title;
        this.artist = artist;
    }
    public void play(){
        System.out.println("Playing " + title + " by " + artist);
    }
}

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在XML文件中装配这个Bean

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       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">

    <!--
    <bean id="compactDisc" class="com.springinaction.cn.SgtPeppers"/>
    -->
    <bean id="compactDisc" class="com.springinaction.cn.BlankDisc">
        <constructor-arg value="Sgt Peppers Lonely Hearts Club Band"/>
        <constructor-arg value="The Beatles"/>
    </bean>

    <bean id="cdPlayer" class="com.springinaction.cn.CDPlayer" c:cd-ref="compactDisc"/>

</beans>

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如果类的构造方法参数中有List类型的参数时，XML配置方法如下：

类：

package com.springinaction.cn;

import java.util.List;

public class BlankDisc implements CompactDisc {
    private String title;
    private String artist;
    private List<String> tracks;
    
    public BlankDisc(String title, String artist){
        this.title = title;
        this.artist = artist;
    }
    
    public BlankDisc(String title, String artist, List<String> tracks){
        this.title = title;
        this.artist = artist;
        this.tracks = tracks;
    }
    
    public void play(){
        System.out.println("Playing " + title + " by " + artist);
    }
}

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XML配置：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       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">

    <!--
    <bean id="compactDisc" class="com.springinaction.cn.SgtPeppers"/>
    -->
    <bean id="compactDisc" class="com.springinaction.cn.BlankDisc">
        <constructor-arg value="Sgt Peppers Lonely Hearts Club Band"/>
        <constructor-arg value="The Beatles"/>
        <constructor-arg>
            <list>
                <value>Sgt Peppers Lonely Hearts Club Band</value>
                <value>With a Little Help From My Friends</value>
                <value>Lucy In The Sky With Diamonds</value>
            </list>
        </constructor-arg>
    </bean>

    <bean id="cdPlayer" class="com.springinaction.cn.CDPlayer" c:cd-ref="compactDisc"/>

</beans>

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（二）使用属性注入

类：

package com.springinaction.cn;

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

@Component
public class CDPlayer {
    private CompactDisc compactDisc;
    @Autowired
    public void setCompactDisc(CompactDisc compactDisc){
        this.compactDisc = compactDisc;
    }

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

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这时候既可以选择构造器注入，也可以使用属性注入，通常的规则是：对于强依赖，使用构造器注入，对于可选的属性使用属性注入。

XML配置（使用P命名空间代替property元素）：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       xmlns:p="http://www.springframework.org/schema/p"
       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">

    <!--
    <bean id="compactDisc" class="com.springinaction.cn.SgtPeppers"/>
    -->
    <bean id="compactDisc" class="com.springinaction.cn.BlankDisc">
        <constructor-arg value="Sgt Peppers Lonely Hearts Club Band"/>
        <constructor-arg value="The Beatles"/>
        <constructor-arg>
            <list>
                <value>Sgt Peppers Lonely Hearts Club Band</value>
                <value>With a Little Help From My Friends</value>
                <value>Lucy In The Sky With Diamonds</value>
            </list>
        </constructor-arg>
    </bean>

    <bean id="cdPlayer" class="com.springinaction.cn.CDPlayer" p:compactDisc-ref="compactDisc"/>

</beans>

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将字面量注入到属性的方法与构造器注入字面量方式类似，示例如下：

类：

package com.springinaction.cn;

import java.util.List;

public class BlankDisc implements CompactDisc {
    private String title;
    private String artist;
    private List<String> tracks;

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

    public void setArtist(String artist) {
        this.artist = artist;
    }

    public void setTracks(List<String> tracks) {
        this.tracks = tracks;
    }

    public void play(){
        System.out.println("Playing " + title + " by " + artist);
    }
}

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XML配置（使用p命名空间）：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       xmlns:p="http://www.springframework.org/schema/p"
       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">

    <!--
    <bean id="compactDisc" class="com.springinaction.cn.SgtPeppers"/>
    -->
    <bean id="compactDisc" class="com.springinaction.cn.BlankDisc" 
          p:title="Sgt Peppers Lonely Heart Club Band"
    p:artist="The Beatles">
        <property name="tracks">
            <list>
                <value>Sgt Peppers Lonely Heart Club Band</value>
                <value>Lucy In The Sky With Diamonds</value>
                <!-- ... more-->
            </list>
        </property>
    </bean>

    <bean id="cdPlayer" class="com.springinaction.cn.CDPlayer" p:compactDisc-ref="compactDisc"/>

</beans>

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四、使用混合装配

（一）多个JavaConfig类进行配置：

在每个配置类上使用@Configuration注解；
在其中一个配置类上使用@Import(AnotherJavaConfigClass.class)即可实现导入；

【也可以在一个统一的JavaConfig类上使用@Import注解导入其他的所有JAVA配置类：@Import(AnotherJavaConfigClass.class, SomeElseJavaConfigClass.class)】

（二）在JavaConfig类中导入在XML中配置的Bean：

在Java配置类上增加一个@ImportResource注解：@ImportResource("classpath:cd-config.xml")

（三）在XML中导入另一个XML配置文件：

在目标XML文件中使用<import>元素：<import resource="cd-config.xml"

（四）没有一个直接的方法能将JavaConfig类导入到xml文件，间接的，通过声明一个配置累的Bean来导入：

注：此文参照中国工信出版社的《Spring实战》第四版一书整理，仅供个人学习记录。

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原文地址：https://www.cnblogs.com/zheng-hong-bo/p/11055285.html