Spring基于Java的配置

以下内容引用自http://wiki.jikexueyuan.com/project/spring/java-based-configuration.html：

基于Java的配置选项，可以使你在不用配置XML的情况下编写大多数的Spring配置。

@Configuration和@Bean注解

带有@Configuration的注解类表示这个类可以使用Spring IoC容器作为bean定义的来源。@Bean注解告诉Spring，一个带有@Bean的注解方法将返回一个对象，该对象应该被注册为在Spring应用程序上下文中的bean。最简单可行的@Configuration类如下所示：

@Configuration
public class HelloWorldConfig {
    
    @Bean
    public HelloWorld helloWorld(){
        return new HelloWorld();
    }

}

对应XML配置如下：

<beans>
   <bean id="helloWorld" class="com.jsoft.testspring.testjavaconfiguration.HelloWorld" />
</beans>

在这里，带有@Bean注解的方法名称作为bean的ID，它创建并返回实际的bean。你的配置类可以声明多个@Bean。一旦定义了配置类，你就可以使用AnnotationConfigApplicationContext来加载并把他们提供给Spring容器，如下所示：

public static void main( String[] args )
{
　　ApplicationContext applicationContext = new AnnotationConfigApplicationContext(HelloWorldConfig.class);
　　HelloWorld helloWorld = applicationContext.getBean(HelloWorld.class);
　　helloWorld.setMessage("Hello World!");
　　helloWorld.getMessage();
}

当然，你可以加载各种配置类，如下所示：

public static void main(String[] args) {
   AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();

   ctx.register(AppConfig.class, OtherConfig.class);
   ctx.register(AdditionalConfig.class);
   ctx.refresh();

   MyService myService = ctx.getBean(MyService.class);
   myService.doStuff();
}

例子：

pom.xml：

<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.jsoft.testspring</groupId>
  <artifactId>testjavaconfiguration</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>testjavaconfiguration</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    
    <!-- Spring Core -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-core -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
     
    <!-- Spring Context -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
    
  </dependencies>
</project>

HelloWorld.java：

package com.jsoft.testspring.testjavaconfiguration;

public class HelloWorld {
    private String message;
    
    public void setMessage(String message){
        this.message = message;
    }
    
    public void getMessage(){
        System.out.println(this.message);
    }
}

HelloWorldConfig.java：

package com.jsoft.testspring.testjavaconfiguration;

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

@Configuration
public class HelloWorldConfig {
    
    @Bean
    public HelloWorld helloWorld(){
        return new HelloWorld();
    }

}

App.java：

package com.jsoft.testspring.testjavaconfiguration;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args )
    {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(HelloWorldConfig.class);
        HelloWorld helloWorld = applicationContext.getBean(HelloWorld.class);
        helloWorld.setMessage("Hello World!");
        helloWorld.getMessage();
    }
}

测试结果：

测试工程：https://github.com/easonjim/5_java_example/tree/master/springtest/test13/testjavaconfiguration

Bean的依赖性注入

当Beans依赖对方时，表达这种依赖性非常简单，只要有一个bean方法调用另一个，如下所示：

@Configuration
public class HelloWorldConfig {
    
    @Bean
    public HelloWorld helloWorld(){
        return new HelloWorld(message());
    }
    
    @Bean
    public String message(){
        return new String("Hello World");
    }

}

可以看出，有依赖性时直接在类中调用新建的方法即可。

例子：

pom.xml：

<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.jsoft.testspring</groupId>
  <artifactId>testjavaconfiguration</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>testjavaconfiguration</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    
    <!-- Spring Core -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-core -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
     
    <!-- Spring Context -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
    
  </dependencies>
</project>

HelloWorld.java：

package com.jsoft.testspring.testjavaconfiguration;

public class HelloWorld {
    private String message;
    
    public HelloWorld(String message){
        this.message = message;
    }
    
    public void getMessage(){
        System.out.println(this.message);
    }
}

HelloWorldConfig.java：

package com.jsoft.testspring.testjavaconfiguration;

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

@Configuration
public class HelloWorldConfig {
    
    @Bean
    public HelloWorld helloWorld(){
        return new HelloWorld(message());
    }
    
    @Bean
    public String message(){
        return new String("Hello World");
    }

}

App.java：

package com.jsoft.testspring.testjavaconfiguration;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args )
    {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(HelloWorldConfig.class);
        HelloWorld helloWorld = applicationContext.getBean(HelloWorld.class);
        helloWorld.getMessage();
    }
}

测试结果：

测试工程：https://github.com/easonjim/5_java_example/tree/master/springtest/test13/testjavaconfiguration1

@Import注释

@import注解允许从另一个配置类中加载Bean定义。如下所示：

@Configuration
public class ConfigA {
   @Bean
   public A a() {
      return new A(); 
   }
}

@Configuration
@Import(ConfigA.class)
public class ConfigB {
   @Bean
   public B b() {
      return new B(); 
   }
}

现在，当实例化上下文时，不需要同时指定ConfigA.class和ConfigB.class，只要ConfigB类需要提供，如下所示：

public static void main(String[] args) {
   ApplicationContext ctx = new AnnotationConfigApplicationContext(ConfigB.class);

   A a = ctx.getBean(A.class);
   B b = ctx.getBean(B.class);
}

例子：

pom.xml：

<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.jsoft.testspring</groupId>
  <artifactId>testjavaconfiguration</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>testjavaconfiguration</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    
    <!-- Spring Core -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-core -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
     
    <!-- Spring Context -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
    
  </dependencies>
</project>

HelloWorld.java：

package com.jsoft.testspring.testjavaconfiguration;

public class HelloWorld {
    private String message;
    
    public HelloWorld(String message){
        this.message = message;
    }
    
    public void getMessage(){
        System.out.println(this.message);
    }
}

HelloWorldConfig.java：

package com.jsoft.testspring.testjavaconfiguration;

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

@Configuration
public class HelloWorldConfig {
    
    @Bean
    public HelloWorld helloWorld(){
        return new HelloWorld(message());
    }
    
    @Bean
    public String message(){
        return new String("Hello World");
    }

}

HelloWorldConfigB.java：

package com.jsoft.testspring.testjavaconfiguration;

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

@Configuration
@Import(HelloWorldConfig.class)
public class HelloWorldConfigB {
    
    @Bean
    public String messageB(){
        return new String("Hello B");
    }
}

App.java：

package com.jsoft.testspring.testjavaconfiguration;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args )
    {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(HelloWorldConfigB.class);
        HelloWorld helloWorld = applicationContext.getBean(HelloWorld.class);
        helloWorld.getMessage();
    }
}

可以看出不用再次引用HelloWorldConfig.java类了。

测试结果：

测试工程：https://github.com/easonjim/5_java_example/tree/master/springtest/test13/testjavaconfiguration2

生命周期回调

@Bean注解支持指定任意的初始化和销毁​​回调方法，这与Spring元素中的Spring XML的init-method和destroy-method属性非常相似。如下所示：

public class Foo {
   public void init() {
      
   }
   public void cleanup() {
      
   }
}

@Configuration
public class AppConfig {
   @Bean(initMethod = "init", destroyMethod = "cleanup" )
   public Foo foo() {
      return new Foo();
   }
}

例子：

pom.xml：

<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.jsoft.testspring</groupId>
  <artifactId>testjavaconfiguration</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>testjavaconfiguration</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    
    <!-- Spring Core -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-core -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
     
    <!-- Spring Context -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
    
  </dependencies>
</project>

HelloWorld.java：

package com.jsoft.testspring.testjavaconfiguration;

public class HelloWorld {
    private String message;
    
    public HelloWorld(String message){
        this.message = message;
    }
    
    public void getMessage(){
        System.out.println(this.message);
    }
    
    public void init(){
        System.out.println("HelloWorld init");
    }
    
    public void cleanup(){
        System.out.println("HelloWorld cleanup");
    }
}

HelloWorldConfig.java：

package com.jsoft.testspring.testjavaconfiguration;

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

@Configuration
public class HelloWorldConfig {
    
    @Bean(initMethod="init",destroyMethod="cleanup")
    public HelloWorld helloWorld(){
        return new HelloWorld(message());
    }
    
    @Bean
    public String message(){
        return new String("Hello World");
    }

}

App.java：

package com.jsoft.testspring.testjavaconfiguration;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args )
    {
        AbstractApplicationContext applicationContext = new AnnotationConfigApplicationContext(HelloWorldConfig.class);
        HelloWorld helloWorld = applicationContext.getBean(HelloWorld.class);
        helloWorld.getMessage();
        applicationContext.registerShutdownHook();
    }
}

测试结果：

测试工程：https://github.com/easonjim/5_java_example/tree/master/springtest/test13/testjavaconfiguration3

指定Bean的作用域范围

默认范围是单实例，但是你可以重写带有@Scope注解的方法，如下所示：

@Configuration
public class AppConfig {
   @Bean
   @Scope("prototype")
   public Foo foo() {
      return new Foo();
   }
}

例子：

pom.xml：

<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.jsoft.testspring</groupId>
  <artifactId>testjavaconfiguration</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>testjavaconfiguration</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    
    <!-- Spring Core -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-core -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
     
    <!-- Spring Context -->
    <!-- http://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
    
  </dependencies>
</project>

HelloWorld.java：

package com.jsoft.testspring.testjavaconfiguration;

public class HelloWorld {
    private String message;
    
    public void setMessage(String message){
        this.message = message;
    }
    
    public void getMessage(){
        System.out.println(this.message);
    }
}

HelloWorldConfig.java：

package com.jsoft.testspring.testjavaconfiguration;

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

@Configuration
public class HelloWorldConfig {
    
    @Bean
    @Scope("prototype")
    public HelloWorld helloWorld(){
        return new HelloWorld();
    }
    
}

@Scope的值和xml中配置的保持一致。

App.java：

package com.jsoft.testspring.testjavaconfiguration;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Hello world!
 *
 */
public class App 
{
    public static void main( String[] args )
    {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(HelloWorldConfig.class);
        HelloWorld helloWorld = applicationContext.getBean(HelloWorld.class);
        helloWorld.setMessage("Hello World 1!");
        helloWorld.getMessage();
        HelloWorld helloWorld2 = applicationContext.getBean(HelloWorld.class);
        helloWorld2.getMessage();
    }
}

测试结果：

测试工程：https://github.com/easonjim/5_java_example/tree/master/springtest/test13/testjavaconfiguration4

更多Java配置的官方例子参考：https://docs.spring.io/spring-javaconfig/docs/1.0.0.M4/reference/html/ch02s02.html