我有这个基本的 spring 应用程序,其中我的 @Autowired
字段的值在输出中为 null。这里有什么问题?
package com.spring;
import org.springframework.beans.factory.annotation.Autowired;
public class HelloWorld {
private String message;
@Autowired
private Double pi;
public HelloWorld(String message){
this.message = message;
}
public void setMessage(String message){
this.message = message;
}
public void getMessage(){
System.out.println("Your Message : " + message);
System.out.println("autowired: "+pi);
}
}
spring.xml 配置文件。
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<bean id="pi" name="pi" class="java.lang.Double" autowire="byName">
<constructor-arg value="3.14"/>
</bean>
<bean id="helloWorld" class="com.spring.HelloWorld">
<constructor-arg ref="msg" />
</bean>
<bean id="msg" class="java.lang.String" >
<constructor-arg value="Hello World"/>
</bean>
</beans>
执行APP的类:
package com.tutorialspoint;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
HelloWorld hw = context.getBean(HelloWorld.class);
hw.getMessage();
System.out.println(context.getBean("msg"));
}
}
输出是:
Your Message Hello World
autowired: null
Hello World
最佳答案
您需要配置上下文以允许 Autowiring 。看到这个答案:
关于java - Spring - 我的 Autowiring 有什么问题?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31159054/