我开始使用Spring DI，但我正在努力应对依赖注入，更糟糕的是我甚至不确定为什么对我来说似乎没问题。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Maven结构的项目：
我在Tomcat 7上运行示例
我在pom.xml中使用了以下依赖项：
简单的想法是拥有一个RESTful服务，通过依赖注入能够打印位于以下位置的配置文件中的属性的值：D:\configuracion.conf.
在 com.diegotutor.utility 我有以下界面：
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 我有RESTful服务，我想使用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
}
}
最后在/com.diegotutor.lessondeliver/src/main/webapp/WEB-INF/service-beans.xml我有以下XML应用程序上下文文件，其中我使用ConfigService (PropertyFileConfigService)的实现注入配置文件的路径：
<?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>
显然我已经在此web.xml网络应用的com.diegotutor.lessondeliver中指定了我想要service-beans.xml作为ConfigLocation和一个监听器ContextLoaderListener，并且RESTful服务依赖在ServletContainer上
如果我正在指定上下文：component-scan在com.diegotutor中按照建议的here查找组件，并且我通过不使用建议的任何新语句强制通过Spring创建对象{{3 }，为什么我将带注释的configService作为null？为什么Spring无法注入com.diegotutor.utility.impl.PropertyFileConfigService的实例？
非常感谢任何帮助！
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>
答案 0 :(得分：21)
你是对的！ 似乎问题是Jersey完全没有意识到Spring并且实例化了它自己的对象。为了让Jersey了解Spring对象的创建（通过依赖注入），我必须集成Spring + Jersey。
要整合：
添加maven依赖项
<dependency>
<groupId>com.sun.jersey.contribs</groupId>
<artifactId>jersey-spring</artifactId>
<version>1.17.1</version>
<exclusions>
<exclusion>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
</exclusion>
<exclusion>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
</exclusion>
<exclusion>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
</exclusion>
<exclusion>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
</exclusion>
</exclusions>
</dependency>
在web.xml
<servlet>
<servlet-name>jersey-servlet</servlet-name>
<servlet-class>
com.sun.jersey.spi.spring.container.servlet.SpringServlet
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
现在@Autowired正常工作，对象不再为空。
我对使用jersey-spring依赖时我必须在maven中使用的排除项有点困惑，但这是另一个问题：）
谢谢！
答案 1 :(得分：5)
将Spring与泽西2 （org.glassfish.*）整合：
某些依赖可能是不必要的，请检查＆amp;事情开始后清除它。
<properties>
<jersey.version>2.5</jersey.version>
</properties>
<!-- Jersey -->
<dependency>
<groupId>org.glassfish.jersey.core</groupId>
<artifactId>jersey-server</artifactId>
<version>${jersey.version}</version>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.containers</groupId>
<!-- if your container implements Servlet API older than 3.0, use "jersey-container-servlet-core" -->
<artifactId>jersey-container-servlet</artifactId>
<version>${jersey.version}</version>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.core</groupId>
<artifactId>jersey-client</artifactId>
<version>${jersey.version}</version>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.test-framework.providers</groupId>
<artifactId>jersey-test-framework-provider-inmemory</artifactId>
<version>${jersey.version}</version>
</dependency>
<!-- Jersey + Spring -->
<dependency>
<groupId>org.glassfish.jersey.ext</groupId>
<artifactId>jersey-spring3</artifactId>
<version>${jersey.version}</version>
<exclusions>
<exclusion>
<groupId>org.springframework</groupId>
<artifactId>spring</artifactId>
</exclusion>
<exclusion>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
</exclusion>
<exclusion>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
</exclusion>
<exclusion>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
</exclusion>
<exclusion>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
</exclusion>
</exclusions>
</dependency>
<servlet>
<servlet-name>my-rest-service</servlet-name>
<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>my.package.with.rest.services</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>my-rest-service</servlet-name>
<url-pattern>/api/*</url-pattern>
</servlet-mapping>
在Spring升级期间，我不得不将其从/main/webapp/WEB-INF/移至/main/resources/（details）。
<?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-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
<context:annotation-config />
<context:component-scan base-package="my.package.with.rest.services" />
</beans>
public interface MyService
{
String work(String s);
}
...
@Service
public class MyServiceImpl implements MyService
{
@Override
public String work(String s)
{
return "Hello, " + s;
}
}
...
@Path("demo/")
@Component
public class DemoRestService
{
@Autowired
private MyService service;
@GET
@Path("test")
public Response test(@FormParam("param") String par)
{
try
{
String entity = service.work(par);
return Response.ok(entity).build();
}
catch (Exception e)
{
e.printStackTrace();
return Response.status(Status.INTERNAL_SERVER_ERROR).entity("Epic REST Failure").build();
}
}
}
答案 2 :(得分：3)
或者您可以简单地扩展SpringBeanAutoWiringSupport类。像这样：public class DemoRestService extends SpringBeanAutoWiringSupport。通过扩展此支持类，可以自动连接服务类的属性。
答案 3 :(得分：2)
另一种可能的选择是在你的球衣资源中手动调用自动装配：
@Context
private ServletContext servletContext;
@PostConstruct
public void init() {
SpringBeanAutowiringSupport.processInjectionBasedOnServletContext(this, servletContext);
}
嗯，你得到一个＆＃34;手动自动装配＆＃34; ...