我刚开始使用Spring DI，但是我在依赖注入方面苦苦挣扎，更糟糕的是，我什至不确定为什么对我来说似乎还可以。希望你们能帮助我！

问题是注释为@Autowired的属性始终为null

我有一些具有Maven结构的项目：

• com.diegotutor.lessondeliver
• com.diegotutor.utility

我正在通过Tomcat 7运行示例

我在我的使用以下依赖项pom.xml：

• spring-context 3.2.4
• spring-web 3.2.4
• jersey-server 1.17.1
• jersey-core 1.17.1
• jersey-servlet 1.17.1

一个简单的想法是拥有一个RESTful服务，该服务通过Dependency Injection能够打印出位于以下位置的配置文件中的属性值： D:\configuracion.conf.

在com.diegotutor.utility，我具有以下接口：

package com.diegotutor.utility;

public interface ConfigService {

    public String getProperty(final String propertyName);
}

实施者：

package com.diegotutor.utility.impl;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.util.Properties;

import com.diegotutor.utility.ConfigService;

public class PropertyFileConfigService implements ConfigService{

Properties prop;

public PropertyFileConfigService (final InputStream input) throws IOException {
    if(input == null) {
        throw new IllegalArgumentException("Input stream can't be null");
    }
    prop = new Properties();
    prop.load(input);
}

public PropertyFileConfigService (final String fileName) throws IOException {
    final FileInputStream input = new FileInputStream(fileName);
    prop = new Properties();
    prop.load(input);
}

public PropertyFileConfigService(final Reader input) throws IOException {
    prop = new Properties();
    prop.load(input);
}

public String getProperty(final String propertyName) {
    return prop.getProperty(propertyName);
}

}

在com.diegotutor.lessondeliver上，我拥有RESTful服务，我想在其中使用ConfigService的注入实例：

package com.diegotutor.lessondeliver;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.diegotutor.utility.ConfigService;

@Path("/")
@Component
public class HelloWorld {

private static final Log log = LogFactory.getLog(HelloWorld.class);

@Autowired
private ConfigService configService;

@Path("/helloworld")
@GET
@Produces(MediaType.TEXT_PLAIN)
public String getHello() {
    String host = configService.getProperty("host");
    return "Hello World! HOST" + host;
            // configService IS NULL!! 
            //SO IT THROWS A NULLPOINTER EXCEPTION WHEN INVOKING getProperty ON IT
}
}

最后，/com.diegotutor.lessondeliver/src/main/webapp/WEB-INF/service-beans.xml在下面的XML应用程序上下文文件中，我使用在其上ConfigService (PropertyFileConfigService)注入配置文件读取路径的实现：

<?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.xsd
   http://www.springframework.org/schema/context
   http://www.springframework.org/schema/context/spring-context.xsd">

<bean id="configService" class="com.diegotutor.utility.impl.PropertyFileConfigService">
    <constructor-arg type="java.lang.String"
        value="D:\configuracion.conf" />
</bean>

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

</beans>

显然，我已在web.xml此com.diegotutor.lessondeliverWeb应用程序的中指定了我希望service-beans.xml作为ConfigLocation和侦听器ContextLoaderListener，并且RESTful服务依赖于ServletContainer

如果我com.diegotutor按照这里的建议指定context：component-scan来查找Components，并且不按照这里的建议使用任何新的Statement来强制通过Spring创建对象，为什么我将带注释的configService设置为null？为什么Spring无法注入的实例com.diegotutor.utility.impl.PropertyFileConfigService？

任何帮助都感激不尽！

谢谢

编辑：

根据要求，我的web.xml如下：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xmlns="http://java.sun.com/xml/ns/javaee" 
xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee     http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" 
id="WebApp_ID" version="3.0">

 <display-name>com.diegotutor.lessondeliver</display-name>

 <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/service-beans.xml</param-value>
 </context-param>

 <listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
 </listener>

 <servlet>
  <servlet-name>jersey-servlet</servlet-name>
  <servlet-class>
         com.sun.jersey.spi.container.servlet.ServletContainer
  </servlet-class>
  <load-on-startup>1</load-on-startup>
 </servlet>

 <servlet-mapping>
  <servlet-name>jersey-servlet</servlet-name>
  <url-pattern>/rest/*</url-pattern>
 </servlet-mapping>
</web-app>