Spring的Java配置方式

@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>；

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>demo.springboot</groupId>
  <artifactId>springboot</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
  
  <dependencies>
  	<dependency>
  		<groupId>org.springframework</groupId>
  		<artifactId>spring-webmvc</artifactId>
  		<version>4.3.11.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>
			</plugins>
		</pluginManagement>
	</build>
  
</project>

pojo

package demo.pojo;

public class User {
	private String username;

    private String password;

    private Integer age;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

dao

package demo.dao;

import java.util.ArrayList;
import java.util.List;

import demo.pojo.User;

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;
    }

}

service

package demo.service;

import java.util.List;

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

import demo.dao.UserDao;
import demo.pojo.User;


@Service
public class UserService {

	@Autowired
	private UserDao dao;
	
	 public List<User> queryUserList() {
		 return dao.queryUserList();
	 }
}

config:java配置

package demo.config;

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

import demo.dao.UserDao;

@Configuration //相当于一个spring.xml
@ComponentScan(basePackages="demo")//配置扫描包
public class SpringConfig {

	@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(){
		return new UserDao(); // 直接new对象
	}
}

测试类

package test;

import java.util.List;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import demo.config.SpringConfig;
import demo.pojo.User;
import demo.service.UserService;

public class SpringBootTest {

	public static void main(String[] args) {
		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
		UserService userService = context.getBean(UserService.class);
		List<User> queryUserList = userService.queryUserList();
		for (User user : queryUserList) {
			System.out.println(user);
		}
		//销毁容器
		context.destroy();
	}
}

使用Java代码就完美的替代xml配置文件，并且结构更加的清晰。