Spring四大注入方式，set注入、构造函数注入、p名称空间注入、spel注入

水深无声 2022-05-21 10:10 309阅读 0赞

## 简单解释一下注入：就是给对象赋值（直接给出代码，解释全部在代码里面 ）    ##

前提是你已经配置好了spring的环境，如果还不会配置可以去看我的入门spring配置

[https://blog.csdn.net/tomwildboar/article/details/80913681][https_blog.csdn.net_tomwildboar_article_details_80913681]

# 1、所用到的实体类 #

###     1-1 car类 ###

package spring.bean;
    
    public class Car {
    	private String color;
    	private String name;
    	public String getColor() {
    		return color;
    	}
    	public void setColor(String color) {
    		this.color = color;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	@Override
    	public String toString() {
    		return "Car [color=" + color + ", name=" + name + "]";
    	}
    	
    }

###     1-2 User类 ###

package spring.bean;
    
    public class User {
    	private String name;
    	private int age;
    	private Car car;
    	
    	
    	public User() {
    		super();
    	}
    	public User(String name, Car car) {
    		
    		this.name = name;
    		this.car = car;
    	}
    	
    	public Car getCar() {
    		return car;
    	}
    	public void setCar(Car car) {
    		this.car = car;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public int getAge() {
    		return age;
    	}
    	public void setAge(int age) {
    		this.age = age;
    	}
    	@Override
    	public String toString() {
    		return "User [name=" + name + ", age=" + age + ", car=" + car + "]";
    	}	
    }

#    2、applicationContext.xml  （核心)     #

<?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:p="http://www.springframework.org/schema/p"  
    		xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd ">
    	 
    	
    	
    	
    	
    	
    	<bean name="user" class="spring.bean.User">
    		
    		<property name="name" value="tom"></property>
    		<property name="age" value="19"></property>
    		
    		<property name="car" ref="car"></property>
    	</bean>
    	
    	
    	<bean name="car" class="spring.bean.Car">
    		<property name="name" value="大众"></property>
    		<property name="color" value="黄色"></property>
    	</bean>
    	
    
    
    	<bean name="user2" class="spring.bean.User">
    		
    		<constructor-arg name="name" value="jerry" index="" type=""></constructor-arg>
    		<constructor-arg name="car" ref="car" index=""></constructor-arg>
    	
    	</bean>
    
    
    
    
    	
    	<bean name="user3" class="spring.bean.User" p:name="jack" p:age="18" p:car-ref="car"></bean>
    
    
    
    	
    		
    		<bean name="user4" class="spring.bean.User" >
    				
    			<property name="name" value="#{user.name}"></property>
    			<property name="age" value="#{user3.age}"></property>
    			<property name="car" ref="car"></property>
    		</bean>
    		
    </beans>

#    3、Demo测试 #

package spring.injection;
    
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import spring.bean.User;
    
    public class Demo {
    	
    	@Test
    	public void fun1(){
    		
    		ApplicationContext ac = new ClassPathXmlApplicationContext("spring/injection/applicationContext.xml");
    		User u = (User) ac.getBean("user");		
    		System.out.println(u);
    		
    	}
    	
    	//构造函数注入
    	@Test
    	public void fun2(){
    		
    		ApplicationContext ac = new ClassPathXmlApplicationContext("spring/injection/applicationContext.xml");
    		User u = (User) ac.getBean("user2");		
    		System.out.println(u);
    		
    	}
    	
    	
    	//p名称空间注入 
    	@Test
    	public void fun3(){
    		
    		ApplicationContext ac = new ClassPathXmlApplicationContext("spring/injection/applicationContext.xml");	
    		User u = (User) ac.getBean("user3");	
    		System.out.println(u);		
    	}
    	
    	//spel注入
    	@Test
    	public void fun4(){
    				
    		ApplicationContext ac = new ClassPathXmlApplicationContext("spring/injection/applicationContext.xml");		
    		User u = (User) ac.getBean("user4");
    		System.out.println(u);
    		
    	}
    	
    }

# 代码亲测有效 #

[https_blog.csdn.net_tomwildboar_article_details_80913681]: https://blog.csdn.net/tomwildboar/article/details/80913681