Spring使用注解代替XML配置

爱被打了一巴掌 2022-06-12 00:53 270阅读 0赞

1.导入命名空间

XML Catalog中除了要导入`spring-beans`以外，还要导入`spring-context`。

2.在applicationContext.xml文件中，添加

<context:component-scan base-package="Object"></context:component-scan>

其中，`base-package`中表示要扫描的包名。我这里表示扫描Object包及其子包下所有的注解。

3.为要创建Bean对象的JAVABean对象添加注解：

@Component("user") //user为Bean的name
    
    //以下三个注解作用和Component完全相同，只是为了在MVC中方便查看
    @Service("user")//service层
    @Controller("user")//web层
    @Repository("user")//dao层

4.设置Bean对象的作用范围

@Scope(scopeName="singleton") //单例
    
    @Scope(scopeName="prototype") //多例

5.属性注入

在要注入属性的**Set方法**上添加注解：

//值类型
    @Value(value="wxs") //wxs为属性值
    
    //对象类型
    @Resource(name="car") //car为Car类的Bean对象

6.生命周期

@PostConstruct//在对象被创建后调用
    
    @PreDestroy//在对象被销毁前掉调用

**Demo:**

<?xml version="1.0" encoding="UTF-8"?>
    
    <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd ">
    
    	<context:component-scan base-package="Object"></context:component-scan>
    	 
    </beans>

//Object.User.java:
    
    package Object;
    import javax.annotation.PostConstruct;
    import javax.annotation.PreDestroy;
    import javax.annotation.Resource;
    
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.context.annotation.Scope;
    import org.springframework.stereotype.Component;
    
    @Component("user")
    @Scope(scopeName="singleton")
    public class User {
    	private String name;
    	private Integer age;
    	private Car car;
    	public Car getCar() {
    		return car;
    	}
    	@Resource(name="car")
    	public void setCar(Car car) {
    		this.car = car;
    	}
    	public String getName() {
    		return name;
    	}
    	@Value("wxs")
    	public void setName(String name) {
    		this.name = name;
    	}
    	public Integer getAge() {
    		return age;
    	}
    	@Value("18")
    	public void setAge(Integer age) {
    		this.age = age;
    	}
    	@Override
    	public String toString() {
    		return "User [name=" + name + ", age=" + age + ", car=" + car + "]";
    	}
    	@PostConstruct
    	public void init(){
    		System.out.println("init...");
    	}
    	@PreDestroy
    	public void destory() {
    		System.out.println("destory...");
    	}
    }

//Object.Car.java:
    
    package Object;
    
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.stereotype.Component;
    
    @Component("car")
    public class Car {
    	private String name;
    	private String color;
    	public String getName() {
    		return name;
    	}
    	@Value("兰博基尼")
    	public void setName(String name) {
    		this.name = name;
    	}
    	public String getColor() {
    		return color;
    	}
    	@Value("绿色")
    	public void setColor(String color) {
    		this.color = color;
    	}
    	@Override
    	public String toString() {
    		return "Car [name=" + name + ", color=" + color + "]";
    	}
    	
    }

//Demo.UserTest.java:
    
    package Demo;
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import Object.User;
    
    public class UserTest {
    	@Test
    	public void f1(){
    		//这里只是为了能够调用ac.close()方法，才使用ClassPathXmlApplicationContext。正常应使用ApplicationContext
    		ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
    		User u = (User)ac.getBean("user");
    		System.out.println(u);
    		ac.close();
    	}
    }

**运行结果：**

init...
    User [name=wxs, age=18, car=Car [name=兰博基尼, color=绿色]]
    destory...