spring 依赖注入

感觉相当于把原来的在代码中赋值改成在xml配置文件中赋值

1 set注入

 1 //需要注入的类
 2 package beans;
 3 public class HelloWorld {
 4     private String msg = null;
 5     public String getMsg() {
 6         return msg;
 7     }
 8     public void setMsg(String msg) {
 9         this.msg = msg;
10     }
11 }

需要注入的类

 1 <!--spring-config.xml 配置文件-->
 2 <?xml version="1.0" encoding="UTF-8"?>
 3 <beans xmlns="http://www.springframework.org/schema/beans"
 4        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 5        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
 6        <!--这里进行注入，其中id值就是测试类中getBean方法里的参数，property的name值就是被注入类中的变量名-->
 7        <bean id="HelloWorld" class="beans.HelloWorld">
 8               <property name="msg" value="HelloWorld"/>
 9        </bean>
10 </beans>

spring-config.xml 配置文件

 1 //测试类
 2 import beans.HelloWorld;
 3 import org.junit.Test;
 4 import org.springframework.context.ApplicationContext;
 5 import org.springframework.context.support.ClassPathXmlApplicationContext;
 6 public class SpringTest {
 7     @Test
 8     public void beanTest() {
 9         ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-config.xml");
10         HelloWorld helloWorld = (HelloWorld) applicationContext.getBean("HelloWorld");
11         System.out.println(helloWorld.getMsg());
12     }
13 }

测试类

2 构造函数注入

 1 //需要注入的类
 2 package beans;
 3 public class HelloWorld {
 4     private String msg = null;
 5     public HelloWorld(String msg) {
 6         this.msg = msg;
 7     }
 8     public String getMsg() {
 9         return msg;
10     }
11 }

需要注入的类

 1 <!--spring-config.xml 配置文件-->
 2 <?xml version="1.0" encoding="UTF-8"?>
 3 <beans xmlns="http://www.springframework.org/schema/beans"
 4        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 5        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
 6        <!--index值表示构造函数中的第几个参数，从0开始数-->
 7        <bean id="HelloWorld" class="beans.HelloWorld">
 8               <constructor-arg index="0" value="Hello Constructor"/>
 9        </bean>
10 </beans>

spring-config.xml 配置文件

测试类同上