Spring的Java配置

Java配置是Spring4.x推薦的配置方式，可以完全替代xml配置。

1、注解Configuration 和 注解@Bean

Spring的Java配置方式是通過 @Configuration 和 @Bean 這兩個注解實現的：

1、@Configuration 作用于類上，相當于一個xml配置文件；

2、@Bean 作用于方法上，相當于xml配置中的<bean id=”” class=””></bean>；

2、示例一

該示例演示了通過Java配置的方式進行配置Spring，并且實現了Spring IOC功能。

（1）創建工程以及導入依賴

<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版本號 -->
????<spring.version>4.3.2.RELEASE</spring.version>
</properties>
<dependencies>
????<!-- 配置servlet -->
????<dependency>
????????<groupId>javax.servlet</groupId>
????????<artifactId>javax.servlet-api</artifactId>
????????<version>3.0.1</version>
????????<scope>provided</scope>
????</dependency>
????<!-- 配置jsp -->
????<dependency>
????????<groupId>javax.servlet.jsp</groupId>
????????<artifactId>javax.servlet.jsp-api</artifactId>
????????<version>2.2.1</version>
????????<scope>provided</scope>
????</dependency>
????<!-- spring4.3.2 -->
????<!-- spring-context -->
????<dependency>
????????<groupId>org.springframework</groupId>
????????<artifactId>spring-context</artifactId>
????????<version>${spring.version}</version>
????</dependency>
????<!-- spring-core -->
????<dependency>
????????<groupId>org.springframework</groupId>
????????<artifactId>spring-core</artifactId>
????????<version>${spring.version}</version>
????</dependency>
????<!-- spring-beans -->
????<dependency>
????????<groupId>org.springframework</groupId>
????????<artifactId>spring-beans</artifactId>
????????<version>${spring.version}</version>
????</dependency>
????<!-- 添加數據庫連接池?druid -->
????<dependency>
????????<groupId>com.alibaba</groupId>
????????<artifactId>druid</artifactId>
????????<version>1.1.3</version>
????</dependency>
????<!-- spring-aop -->
????<dependency>
????????<groupId>org.springframework</groupId>
????????<artifactId>spring-aop</artifactId>
????????<version>${spring.version}</version>
????</dependency>
????<!-- aspectjweaver -->
????<dependency>
????????<groupId>org.aspectj</groupId>
????????<artifactId>aspectjweaver</artifactId>
????????<version>1.6.11</version>
????</dependency>
????<!-- aspectjrt -->
????<dependency>
????????<groupId>org.aspectj</groupId>
????????<artifactId>aspectjrt</artifactId>
????????<version>1.6.11</version>
????</dependency>
????<!-- 數據庫驅動 -->
????<dependency>
????????<groupId>mysql</groupId>
????????<artifactId>mysql-connector-java</artifactId>
????????<version>5.1.6</version>
????</dependency>
</dependencies>

（2）編寫DAO層類UserDao用于模擬與數據庫的交互

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）編寫Service層LoginService 類

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層
????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;
????}
}

?

編寫控制器

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）編寫SpringConfig類（配置類）

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 配置類 相當于之前的xml文件
?* @Configuration 等同于spring的XML配置文件；使用Java代碼可以檢查類型安全。
?* @Bean：用@Bean標注方法等價于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();
????????//將userDao注入service
????????((UserServiceImpl) userService).setUserDao(getUserDaoBean());
????????return userService;
????}

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

}

（6）編寫測試方法用于啟動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) {
????????// 加載配置類(等同于以前加載applicationContext.xml)
????????AnnotationConfigApplicationContext context =
????????????????new AnnotationConfigApplicationContext(SpringConfig.class);
????????// 從ioc容器中獲取控制器對象
????????UserController userController = context.getBean(UserController.class);
????????// 調用控制器方法
????????userController.login();
????}
}

（7）小結

從以上的示例中可以看出，使用Java代碼就完美的替代xml配置文件，并且結構更加的清晰。

【補充】或者使用@Repository，@Service，@Controller?

SpringConfig不用寫方法，在類上加上 @Configuration @ComponentScan(basePackages = "com.henu")

運行APP即可。

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