Spring @Configuration详解

@Configuration用于定义配置类，可替换xml配置文件，被注解的类内部包含有一个或多个被@Bean注解的方法，这些方法将会被AnnotationConfigApplicationContext或AnnotationConfigWebApplicationContext类进行扫描，并用于构建bean定义，初始化Spring容器。

注意：@Configuration注解的配置类有如下要求：

1. @Configuration不可以是final类型；
2. @Configuration不可以是匿名类；
3. 嵌套的configuration必须是静态类。

一、@Configuation加载Spring方法

1.1、@Configuration配置spring并启动spring容器

@Configuration标注在类上，相当于把该类作为spring的xml配置文件中的<beans>，作用为：配置spring容器(应用上下文)

package com.ahies.ija.management.util;

/**
 * @Description TODO
 * @Date 2019/3/8 9:59
 * @Author zsj
 */
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.awt.*;
import java.io.File;

@Configuration
public class TestConfiguration {
    public TestConfiguration() {
        System.out.println("TestConfiguration容器启动初始化。。。");
    }

  
}

测试方法

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

public class TestMain {
    public static void main(String[] args) {

        // @Configuration注解的spring容器加载方式，用AnnotationConfigApplicationContext替换ClassPathXmlApplicationContext
        ApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);

        // 如果加载spring-context.xml文件：
        // ApplicationContext context = new
        // ClassPathXmlApplicationContext("spring-context.xml");
    }
}

1.2、@Configuration启动容器+@Bean注册Bean，@Bean下管理bean的生命周期

@Bean标注在方法上(返回某个实例的方法)，等价于spring的xml配置文件中的<bean>，作用为：注册bean对象

bean类：

package com.ahies.ija.management.util;

/**
 * @Description TODO
 * @Date 2019/3/8 10:00
 * @Author zsj
 */

public class TestBean {

    private String username;
    private String url;
    private String password;

    public void sayHello() {
        System.out.println("TestBean sayHello...");
    }

    public String toString() {
        return "username:" + this.username + ",url:" + this.url + ",password:" + this.password;
    }

    public void start() {
        System.out.println("TestBean 初始化。。。");
    }

    public void cleanUp() {
        System.out.println("TestBean 销毁。。。");
    }
}

配置类：

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

@Configuration
public class TestConfiguration {
    public TestConfiguration() {
        System.out.println("TestConfiguration容器启动初始化。。。");
    }

    // @Bean注解注册bean,同时可以指定初始化和销毁方法
    // @Bean(name="testBean",initMethod="start",destroyMethod="cleanUp")
    @Bean
    @Scope("prototype")
    public TestBean testBean() {
        return new TestBean();
    }
}

主方法测试类：

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

public class TestMain {
    public static void main(String[] args) {

        // @Configuration注解的spring容器加载方式，用AnnotationConfigApplicationContext替换ClassPathXmlApplicationContext
        ApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);

        // 如果加载spring-context.xml文件：
        // ApplicationContext context = new
        // ClassPathXmlApplicationContext("spring-context.xml");
        
         //获取bean
        TestBean tb = (TestBean) context.getBean("testBean");
        tb.sayHello();
    }
}

1.3、@Configuration启动容器+@Component注册Bean

bean类：

import org.springframework.stereotype.Component;

//添加注册bean的注解
@Component
public class TestBean {

    private String username;
    private String url;
    private String password;

    public void sayHello() {
        System.out.println("TestBean sayHello...");
    }

    public String toString() {
        return "username:" + this.username + ",url:" + this.url + ",password:" + this.password;
    }

    public void start() {
        System.out.println("TestBean 初始化。。。");
    }

    public void cleanUp() {
        System.out.println("TestBean 销毁。。。");
    }
}

配置类：

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

@Configuration
//添加自动扫描注解，basePackages为TestBean包路径
@ComponentScan(basePackages = "com.ahies.ija.management")
public class TestConfiguration {
    public TestConfiguration() {
        System.out.println("TestConfiguration容器启动初始化。。。");
    }


}

主方法测试获取bean对象：

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

public class TestMain {
    public static void main(String[] args) {

        // @Configuration注解的spring容器加载方式，用AnnotationConfigApplicationContext替换ClassPathXmlApplicationContext
        ApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);

        // 如果加载spring-context.xml文件：
        // ApplicationContext context = new
        // ClassPathXmlApplicationContext("spring-context.xml");
        
         //获取bean
        TestBean tb = (TestBean) context.getBean("testBean");
        tb.sayHello();
    }
}

1.6、@Configuation总结

 @Configuation等价于<Beans></Beans>

 @Bean等价于<Bean></Bean>

 @ComponentScan等价于<context:component-scan base-package="com.ahies.ija.management"/>

二、组合多个配置类

2.1、在@configuration中引入spring的xml配置文件

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

@Configuration
@ImportResource("classpath:applicationContext-configuration.xml")
public class WebConfig {
}

bean类：

public class TestBean2 {
    private String username;
    private String url;
    private String password;

    public void sayHello() {
        System.out.println("TestBean2 sayHello...");
    }

    public String toString() {
        return "TestBean2 username:" + this.username + ",url:" + this.url + ",password:" + this.password;
    }

    public void start() {
        System.out.println("TestBean2 初始化。。。");
    }

    public void cleanUp() {
        System.out.println("TestBean2 销毁。。。");
    }
}

测试类：

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

public class TestMain2 {
    public static void main(String[] args) {

        // @Configuration注解的spring容器加载方式，用AnnotationConfigApplicationContext替换ClassPathXmlApplicationContext
        ApplicationContext context = new AnnotationConfigApplicationContext(WebConfig.class);

        // 如果加载spring-context.xml文件：
        // ApplicationContext context = new
        // ClassPathXmlApplicationContext("spring-context.xml");

        // 获取bean
        TestBean2 tb = (TestBean2) context.getBean("testBean2");
        tb.sayHello();
    }
}

 2.2、在@configuration中引入其它注解配置

package com.ahies.ija.management.util;

/**
 * @Description TODO
 * @Date 2019/3/8 13:04
 * @Author zsj
 */
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.ImportResource;


@Configuration
//@ImportResource("classpath:applicationContext-configuration.xml")
@Import(TestConfiguration.class)
public class WebConfig {
}

测试类：

package com.ahies.ija.management.util;

/**
 * @Description TODO
 * @Date 2019/3/8 13:05
 * @Author zsj
 */
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;



public class TestMain2 {
    public static void main(String[] args) {

        // @Configuration注解的spring容器加载方式，用AnnotationConfigApplicationContext替换ClassPathXmlApplicationContext
        ApplicationContext context = new AnnotationConfigApplicationContext(WebConfig.class);

        // 如果加载spring-context.xml文件：
        // ApplicationContext context = new
        // ClassPathXmlApplicationContext("spring-context.xml");

        // 获取bean

        TestBean tb = (TestBean) context.getBean("testBean");
        tb.sayHello();
    }
}

2.3、@configuration嵌套（嵌套的Configuration必须是静态类）

通过配置类嵌套的配置类，达到组合多个配置类的目的。但注意内部类必须是静态类。

上代码：

package com.ahies.ija.management.util;

/**
 * @Description TODO
 * @Date 2019/3/8 9:59
 * @Author zsj
 */
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.awt.*;
import java.io.File;

@Configuration
public class TestConfiguration {
    public TestConfiguration() {
        System.out.println("TestConfiguration容器启动初始化。。。");
    }

    // @Bean注解注册bean,同时可以指定初始化和销毁方法
     @Bean(name="testBean",initMethod="start",destroyMethod="cleanUp")
//    @Bean
    public TestBean testBean() {
        return new TestBean();
    }

    @Configuration
    static class DatabaseConfig {
        @Bean
        File file() {
            return new File("/");
        }
    }
}

启动类

package com.ahies.ija.management.util;

/**
 * @Description TODO
 * @Date 2019/3/8 9:59
 * @Author zsj
 */
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import java.io.File;

public class TestMain {
    public static void main(String[] args) {

        // @Configuration注解的spring容器加载方式，用AnnotationConfigApplicationContext替换ClassPathXmlApplicationContext
        ApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);

        // 如果加载spring-context.xml文件：
        // ApplicationContext context = new
        // ClassPathXmlApplicationContext("spring-context.xml");
        //获取bean
        TestBean tb = (TestBean) context.getBean("testBean");
        tb.sayHello();
        File ds = (File) context.getBean("file");
        System.out.println(ds);
    }
}