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：

@Configuration不可以是final类型；
@Configuration不可以是匿名类；
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ClassPathXmlApplicationContextApplicationContext 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ClassPathXmlApplicationContextApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);// 如果加载spring-context.xml文件：// ApplicationContext context = new// ClassPathXmlApplicationContext("spring-context.xml");//获取beanTestBean 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ClassPathXmlApplicationContextApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);// 如果加载spring-context.xml文件：// ApplicationContext context = new// ClassPathXmlApplicationContext("spring-context.xml");//获取beanTestBean 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ClassPathXmlApplicationContextApplicationContext context = new AnnotationConfigApplicationContext(WebConfig.class);// 如果加载spring-context.xml文件：// ApplicationContext context = new// ClassPathXmlApplicationContext("spring-context.xml");// 获取beanTestBean2 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ClassPathXmlApplicationContextApplicationContext context = new AnnotationConfigApplicationContext(WebConfig.class);// 如果加载spring-context.xml文件：// ApplicationContext context = new// ClassPathXmlApplicationContext("spring-context.xml");// 获取beanTestBean 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")
//    @Beanpublic TestBean testBean() {return new TestBean();}@Configurationstatic class DatabaseConfig {@BeanFile 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ClassPathXmlApplicationContextApplicationContext context = new AnnotationConfigApplicationContext(TestConfiguration.class);// 如果加载spring-context.xml文件：// ApplicationContext context = new// ClassPathXmlApplicationContext("spring-context.xml");//获取beanTestBean tb = (TestBean) context.getBean("testBean");tb.sayHello();File ds = (File) context.getBean("file");System.out.println(ds);}
}