Spring初学日记（三） --利用注解方式实现代码功能

港控/mmm° 2022-05-19 04:38 231阅读 0赞

一.在编写代码的时候，配置xml文件有时候会很麻烦，可以利用注释方式来配置文件之间的传输。

第一种：

applicationContext.xml。在原来的代码基础上，添加了 <context:annotation-config/>表示告诉Spring要用注解的方式进行配置

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
        xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="
       http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
       http://www.springframework.org/schema/aop
       http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
       http://www.springframework.org/schema/tx
       http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
       http://www.springframework.org/schema/context     
       http://www.springframework.org/schema/context/spring-context-3.0.xsd">
      
        <context:annotation-config/>
        <bean name="c" class="com.how2java.pojo.Category">
            <property name="name" value="category 1" />
        </bean>
        <bean name="p" class="com.how2java.pojo.Product">
            <property name="name" value="product1" />
        </bean>
      
    </beans>

在Product.java的category属性前加上@Autowired注解，@Autowired 注释，它可以对类成员变量、方法及构造函数进行标注，完成自动装配的工作。 通过 @Autowired的使用来消除 set ，get方法。

Autowired   auto自动的，wired接有电线的。自动连接属性配置。

package com.how2java.pojo;
     
    import org.springframework.beans.factory.annotation.Autowired;
     
    public class Product {
     
        private int id;
        private String name;
        @Autowired
        private Category category;
     
        public int getId() {return id;}
        public void setId(int id) {this.id = id;}
        public String getName() {return name;}
        public void setName(String name) {this.name = name;}
        public Category getCategory() { return category;}
        public void setCategory(Category category) {this.category = category;}
    }

测试代码：Category类在前面的学习笔记里面有，直接拿过来用就行

package com.how2java.test;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.how2java.pojo.Product;
    
    public class TestSpring {
    
    	public static void main(String[] args) {
    		ApplicationContext context = new ClassPathXmlApplicationContext(new String[] { "applicationContext.xml" });
    		Product p = (Product) context.getBean("p");
    		System.out.println(p.getName());
    		System.out.println(p.getCategory().getName());
    	}
    }

运行结果：

product1
    category 1

资源地址：

链接：https://pan.baidu.com/s/1G77KX2CPh9Mz4N9f94-rmQ 密码：6eyd

二.在此基础上也可以采用@Resource

@Resourcepackage com.how2java.pojo;
    
    import javax.annotation.Resource;
    
    public class Product {
    
    	private int id;
    	private String name;
    	@Resource(name="c")
    	private Category category;
    
    	public int getId() {
    		return id;
    	}
    
    	public void setId(int id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public Category getCategory() {
    		return category;
    	}
    	
    	public void setCategory(Category category) {
    		this.category = category;
    	}
    }

修改applicationContext.xml，什么都去掉，只新增：

<context:component-scan base-package="com.how2java.pojo"/>

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
        xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="
       http://www.springframework.org/schema/beans 
       http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
       http://www.springframework.org/schema/aop 
       http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
       http://www.springframework.org/schema/tx 
       http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
       http://www.springframework.org/schema/context      
       http://www.springframework.org/schema/context/spring-context-3.0.xsd">
     
     	<context:component-scan base-package="com.how2java.pojo"/>
     	
    </beans>

为Product类加上@Component注解，即表明此类是bean

@Component("p")
    public class Product {

为Category 类加上@Component注解，即表明此类是bean

@Component("c")
    public class Category {

另外，因为配置从applicationContext.xml中移出来了，所以属性初始化放在属性声明上进行了。

private String name="product 1";
    private String name="category 1";

在测试一下就行了：

package com.how2java.test;
     
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
     
    import com.how2java.pojo.Product;
     
    public class TestSpring {
     
        public static void main(String[] args) {
            ApplicationContext context = new ClassPathXmlApplicationContext(new String[] { "applicationContext.xml" });
            Product p = (Product) context.getBean("p");
            System.out.println(p.getName());
            System.out.println(p.getCategory().getName());
        }
    }