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Java配置是Spring4.x推荐的配置方式，完全替代xml配置

@Configuration 和 @Bean
Spring的Java配置方式是通过 @Configuration 和 @Bean 这两个注解实现的：
1、@Configuration 作用于类上，相当于一个xml配置文件；
2、@Bean 作用于方法上，相当于xml配置中的<bean>；

创建maven项目，导入依赖

<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.dynamic.springconfig</groupId><artifactId>dynamic-springconfig</artifactId><version>0.0.1-SNAPSHOT</version><packaging>war</packaging><name>dynamic-springconfig</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><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>4.3.7.RELEASE</version></dependency><!-- 连接池 --><dependency><groupId>com.jolbox</groupId><artifactId>bonecp-spring</artifactId><version>0.8.0.RELEASE</version></dependency></dependencies><build><finalName>${project.artifactId}</finalName><plugins><!-- 资源文件拷贝插件 --><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-resources-plugin</artifactId><configuration><encoding>UTF-8</encoding></configuration></plugin><!-- Java编译插件 --><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><configuration><source>1.7</source><target>1.7</target><encoding>UTF-8</encoding></configuration></plugin></plugins><pluginManagement><plugins><!-- 配置Tomcat插件 --><plugin><groupId>org.apache.tomcat.maven</groupId><artifactId>tomcat7-maven-plugin</artifactId><version>2.2</version></plugin><!--  添加配置，放过该错误提示。web.xml is missing and <failOnMissingWebXml> is set to true--><plugin>  <groupId>org.apache.maven.plugins</groupId>  <artifactId>maven-war-plugin</artifactId>  <version>2.2</version>  <configuration>  <failOnMissingWebXml>false</failOnMissingWebXml>  </configuration>  </plugin> </plugins></pluginManagement></build></project>

一.使用Java配置方式

User实体

package com.dynamic.springconfig;
public class User {private String username;private String password;private Integer age;
}

package com.dynamic.springconfig;
import java.util.ArrayList;
import java.util.List;public class UserDao {public List<User> queryUserList(){List<User> result = new ArrayList<User>();//模拟数据库的查询for(int i =0;i<10;i++){User user = new User();user.setUsername("username_" + i);user.setPassword("password_" + i);user.setAge(i+1);result.add(user);}return result;}
}

package com.dynamic.springconfig;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;@Service
public class UserService {@Autowiredprivate UserDao userDao;public List<User> queryUserList(){return this.userDao.queryUserList();}}

package com.dynamic.springconfig;
import java.util.List;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;/*** Hello world!*/
@Configuration//通过该注解来表明该类是一个Spring的配置，相当于一个xml文件
@ComponentScan(basePackages="com.dynamic.springconfig")//扫描包
@PropertySource(value= {"classpath:test.properties"},ignoreResourceNotFound = false)
public class App 
{	@Value("${test}")private String test;@Bean //通过该注解来表明是一个Bean对象，相当于xml中的<bean>public  UserDao getUserDao(){System.out.println(test);return new UserDao();}public static void main( String[] args ){ 	//通过Java配置来实例化Spring容器AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(App.class);	//在Spring容器中获取Bean对象UserService userService = context.getBean(UserService.class);//调用对象中的方法List<User> List = userService.queryUserList();for(User user:List){System.out.println(user.getUsername() + ","+ user.getAge());}}
}

启动类中可以看到它声明为配置类，配置了包扫描，读取属性文件。

test.properties

test=success

对比使用xml配置。在源代码的基础上，我们加入配置文件。

applicationContext.xml

<?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:context="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd"><context:component-scan base-package="com.dynamic.springconfig"></context:component-scan><context:property-placeholder location="test.properties"/><bean id="userDao" class="com.dynamic.springconfig.UserDao"></bean></beans>

package com.dynamic.springxml;
import java.util.List;import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.dynamic.springconfig.User;
import com.dynamic.springconfig.UserService;public class AppXml {@Value("${test}")private String test;public static void main(String[] args){ApplicationContext context = new  ClassPathXmlApplicationContext("applicationContext.xml");UserService userService = (UserService) context.getBean("userService");List<User> list =userService.queryUserList(); for(User user:list){System.out.println(user.getUsername() + ","+ user.getAge());}		}
}