SpringBoot（二）：Spring的JAVA配置方式

超、凢脫俗 2022-05-26 11:48 172阅读 0赞

说明：Java配置是Spring4.x推荐的配置方式，可以完全替代xml配置。

1.重要注解@Configuration和@Bean

1.1@Configuration作用于类上，相当于一个xml配置文件；

1.2@Bean作用于方法上，相当于xml配置中的<bean>；

2.示例

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。

2.1创建工程以及导入依赖

2.1.1pom.xml文件配置：

<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>cn.itcast.springboot</groupId>
    	<artifactId>itcast-springboot</artifactId>
    	<version>1.0.0-SNAPSHOT</version>
    	<packaging>war</packaging>
    
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework</groupId>
    			<artifactId>spring-webmvc</artifactId>
    			<version>4.3.7.RELEASE</version>
    		</dependency>
    		
    		<dependency>
    			<groupId>com.jolbox</groupId>
    			<artifactId>bonecp-spring</artifactId>
    			<version>0.8.0.RELEASE</version>
    		</dependency>
    	</dependencies>
    	<build>
    		<finalName>${project.artifactId}</finalName>
    		<plugins>
    			
    			<plugin>
    				<groupId>org.apache.maven.plugins</groupId>
    				<artifactId>maven-resources-plugin</artifactId>
    				<configuration>
    					<encoding>UTF-8</encoding>
    				</configuration>
    			</plugin>
    			
    			<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>
    				
    				<plugin>
    					<groupId>org.apache.tomcat.maven</groupId>
    					<artifactId>tomcat7-maven-plugin</artifactId>
    					<version>2.2</version>
    				</plugin>
    			</plugins>
    		</pluginManagement>
    	</build>
    </project>

2.2创建User实体类

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;
        }
    
    }

2.3创建UserDao类用于模拟与数据库的交互

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;
        }
    
    }

2.4创建UserService类用于实现User数据操作业务逻辑

@Service
    public class UserService {
    
        @Autowired // 注入Spring容器中的bean对象
        private UserDAO userDAO;
    
        public List<User> queryUserList() {
            // 调用userDAO中的方法进行查询
            return this.userDAO.queryUserList();
        }
    
    }

2.5创建SpringConfig类用户实例化Spring容器

@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 = "cn.itcast.springboot.javaconfig") //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对象做演示
        }
        
    }

2.6编写测试方法用于启动Spring容器

public class Main {
        
        public static void main(String[] args) {
            // 通过Java配置来实例化Spring容器
            AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.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.getPassword() + ", " + user.getPassword());
            }
            
            // 销毁该容器
            context.destroy();
        }
    
    }

2.7测试效果

username_0, password_0, password_0
    username_1, password_1, password_1
    username_2, password_2, password_2
    username_3, password_3, password_3
    username_4, password_4, password_4
    username_5, password_5, password_5
    username_6, password_6, password_6
    username_7, password_7, password_7
    username_8, password_8, password_8
    username_9, password_9, password_9