无法让Spring注入我的依赖 [英] Can't get Spring to inject my dependencies
问题描述
我一直试图让Spring在我的应用程序中注入一个@Autowired依赖项，但无济于事。我在做什么错？
I've been trying to get Spring to inject an @Autowired dependency into my application without avail. What am I doing wrong?
我创建了一个名为TimeService的bean。
I created a bean called TimeService. Its job is to return the current time to anyone that asks.
package com.foxbomb.springtest.domain.time;
import java.util.Date;
import org.springframework.stereotype.Service;
@Service
public class TimeService {
public TimeService() {
super();
System.out.println("Instantiating TimeService...");
}
public Date getTime() {
return new Date();
}
}
当然，我需要告诉Spring，因此我在web.xml中添加了以下内容：
Of course, I need to tell Spring about this, so I added the following to web.xml:
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/spring-context.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
很好，还有一些Spring配置：
Great, and some Spring configuration:
<?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: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/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:annotation-config base-package="com.foxbomb.springtest.domain" />
</beans>
现在，我们需要的是一个希望使用此依赖项的调用类。不幸的是，这里的@Autowired似乎什么也没做：
Now all we need is a calling class that would like to use this dependency. Unfortunately, the @Autowired here seems to do nothing:
package com.foxbomb.springtest;
import...
@Configurable
public class TimeManager {
public TimeManager() {
super();
System.out.println("Instantiating TimeManager...");
}
@Autowired
private TimeService timeService;
public Date getTime() {
return timeService.getTime();
}
}
最后，想要一个JSP显示时间：
And lastly, a JSP that wants to display the time:
<%@page import="com.foxbomb.springtest.ApplicationContextImpl"%>
<%@page import="com.foxbomb.springtest.TimeManager"%>
<html>
<head>
<title>Spring Test</title>
</head>
<body>
<h1>Autowired Dependencies....</h1>
<p>
Time is now <%=new TimeManager().getTime()%>!
</p>
</body>
</html>
但是我得到的只是：
java.lang.NullPointerException
com.foxbomb.springtest.TimeManager.getTime(TimeManager.java:26)
推荐答案
最后！
我在上面的代码中使用了它例。诀窍是设置Aspect / J和Weaving。这允许@Configurable带注释的类自动实现其对Spring的依赖以注入依赖项。
I got it working with the code in the above example. The trick was to set up Aspect/J and Weaving. This allows the @Configurable annotated class to automatically realize that its dependent on Spring to inject dependencies.
基本包没有多大问题：）我不小心使一个xml错字，尝试将base-package属性添加到context：annotation-config标记。正确的定义是：
There wasn't much wrong with the base package :) I accidentally made a xml typo, trying to add the base-package attribute to the context:annotation-config tag. The correct definition was:
<context:annotation-config/>
<context:component-scan base-package="com.foxbomb.springtest"/>
我实际上最终需要将其更改为com.foxbomb.springtext，以包括尝试使用的类
I need actually eventually need to change it to com.foxbomb.springtext to include the class that was trying to access the bean too - as in the end it's also annotated.
感谢大家的帮助！
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