Spring的Java配置

Java配置是Spring4.x推荐的配置方式，可以完全替代xml配置。

1、注解Configuration 和注解@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 id=”” class=””></bean>；

2、示例一

该示例演示了通过Java配置的方式进行配置Spring，并且实现了Spring IOC功能。

（1）创建工程以及导入依赖

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    
    <spring.version>4.3.2.RELEASE</spring.version>
</properties>
<dependencies>
    
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.0.1</version>
        <scope>provided</scope>
    </dependency>
    
    <dependency>
        <groupId>javax.servlet.jsp</groupId>
        <artifactId>javax.servlet.jsp-api</artifactId>
        <version>2.2.1</version>
        <scope>provided</scope>
    </dependency>
    
    
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>${spring.version}</version>
    </dependency>
    
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>${spring.version}</version>
    </dependency>
    
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-beans</artifactId>
        <version>${spring.version}</version>
    </dependency>
    
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.1.3</version>
    </dependency>
    
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-aop</artifactId>
        <version>${spring.version}</version>
    </dependency>
    
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>1.6.11</version>
    </dependency>
    
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjrt</artifactId>
        <version>1.6.11</version>
    </dependency>
    
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.6</version>
    </dependency>
</dependencies>

（2）编写DAO层类UserDao用于模拟与数据库的交互

ipackage com.henu.dao;

public interface UserDao {
void login();
}

package com.henu.dao;

/**
* @author George
* @description
**/
public class UserDaoImpl implements UserDao {
    @Override
    public void login() {
        System.out.println("UserDao:login()");
    }
}

（3）编写Service层LoginService 类

package com.henu.service;

import com.henu.dao.UserDao;

public interface UserService {
void login();
}

package com.henu.service;

import com.henu.dao.UserDao;

/**
* @author George
* @description
**/
public class UserServiceImpl implements UserService {

//注入dao层
private UserDao userDao;

@Override
    public void login() {
        System.out.println("UserService:login()");
        userDao.login();
    }

public UserDao getUserDao() {
return userDao;
}

public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
}

编写控制器

package com.henu.controller;

import com.henu.service.UserService;

/**
* @author George
* @description
**/
public class UserController {

private UserService userService;

public String login(){
        System.out.println("UserController:login()");
        userService.login();
        return "login";
    }

public UserService getUserService() {
return userService;
}

public void setUserService(UserService userService) {
this.userService = userService;
}
}

（5）编写SpringConfig类（配置类）

package com.henu.config;

import com.henu.controller.UserController;
import com.henu.dao.UserDao;
import com.henu.dao.UserDaoImpl;
import com.henu.service.UserService;
import com.henu.service.UserServiceImpl;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
* @author George
* @description 配置类相当于之前的xml文件
* @Configuration 等同于spring的XML配置文件；使用Java代码可以检查类型安全。
* @Bean：用@Bean标注方法等价于XML中配置的bean。
**/
@Configuration
public class SpringConfig {

@Bean
    public UserDao getUserDaoBean(){
        UserDao userDao = new UserDaoImpl();
        return userDao;
    }

@Bean
    public UserService getUserServiceBean(){
        UserService userService = new UserServiceImpl();
        //将userDao注入service
        ((UserServiceImpl) userService).setUserDao(getUserDaoBean());
        return userService;
    }

@Bean
    public UserController getUserControllerBean(){
        UserController userController = new UserController();
        userController.setUserService(getUserServiceBean());
        return userController;
    }

}

（6）编写测试方法用于启动Spring容器

package com.henu;

import com.henu.config.SpringConfig;
import com.henu.controller.UserController;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
* @author George
* @description
**/
public class App {
    public static void main(String[] args) {
        // 加载配置类(等同于以前加载applicationContext.xml)
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(SpringConfig.class);
        // 从ioc容器中获取控制器对象
        UserController userController = context.getBean(UserController.class);
        // 调用控制器方法
        userController.login();
    }
}

（7）小结

从以上的示例中可以看出，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。

【补充】或者使用@Repository，@Service，@Controller

SpringConfig不用写方法，在类上加上

@Configuration
@ComponentScan(basePackages = "com.henu")

运行APP即可。