我知道这个问题被多次询问，但我现在看了几个晚上，我似乎无法找出为什么Autowired字段保持为空。我盯着它看，所以也许你们中的某些人看到了什么是错的。
我有以下代码：
ApplicationContext.xml
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" 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-4.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd ">
<context:component-scan base-package="com.skoerkamp"/>
<import resource="ApplicationContext-persistence.xml"/>
</beans>
的ApplicationContext-的persistence.xml
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">
<tx:annotation-driven transaction-manager="transactionManager"/>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory"/>
</bean>
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="packagesToScan" value="com.skoerkamp.model"/>
<property name="dataSource" ref="dataSource"/>
<property name="persistenceUnitName" value="GP_UNIT"/>
<property name="jpaProperties">
<props>
<prop key="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</prop>
<!--
<prop key="hibernate.hbm2ddl.auto">create-drop</prop>
-->
</props>
</property>
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="showSql" value="false"/>
<property name="generateDdl" value="false"/>
</bean>
</property>
</bean>
<!-- DB configuration -->
<bean name="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
<property name="url" value="<connection-url>"/>
<property name="username" value="<user>"/>
<property name="password" value="<pw>"/>
</bean>
</beans>
的pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.skoerkamp</groupId>
<artifactId>groupplanner</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>Group Planner Server</name>
<url>http://maven.apache.org</url>
<repositories>
<repository>
<id>maven2-repository.java.net</id>
<name>Java.net Repository for Maven</name>
<url>http://download.java.net/maven/2/</url>
<layout>default</layout>
</repository>
</repositories>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.8.2</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.sun.jersey</groupId>
<artifactId>jersey-server</artifactId>
<version>1.8</version>
</dependency>
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20141113</version>
</dependency>
<dependency>
<groupId>javax.ws.rs</groupId>
<artifactId>jsr311-api</artifactId>
<version>1.1.1</version>
</dependency>
<!-- Spring -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>4.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>4.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>3.0.4.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>4.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>4.0.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-orm</artifactId>
<version>4.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>4.1.3.RELEASE</version>
</dependency>
<!--Database-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.24</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>5.1.3.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.3.7.Final</version>
</dependency>
</dependencies>
<build>
<finalName>groupplanner</finalName>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.2</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
<plugin>
<artifactId>maven-failsafe-plugin</artifactId>
<version>2.6</version>
<executions>
<execution>
<goals>
<goal>integration-test</goal>
<goal>verify</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<version>6.1.16</version>
<configuration>
<scanIntervalSeconds>10</scanIntervalSeconds>
<stopPort>8005</stopPort>
<stopKey>STOP</stopKey>
<webApp>
<contextPath>/groupplanner</contextPath>
</webApp>
</configuration>
<executions>
<execution>
<id>start-jetty</id>
<phase>pre-integration-test</phase>
<goals>
<goal>run</goal>
</goals>
<configuration>
<scanIntervalSeconds>0</scanIntervalSeconds>
<daemon>true</daemon>
</configuration>
</execution>
<execution>
<id>stop-jetty</id>
<phase>post-integration-test</phase>
<goals>
<goal>stop</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
仅出于测试目的，只需拨打我的服务即可。
package com.skoerkamp.rest;
import com.skoerkamp.service.CalendarService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
@Path("/calendar")
@Service
public class CalendarEndpoint {
@Autowired
private CalendarService calendarService;
@GET
public String getCalendarItems() {
calendarService.create();
return "";
}
}
服务：
package com.skoerkamp.service;
import com.skoerkamp.model.CalendarItem;
import com.skoerkamp.repository.CalendarRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;
@Service
public class CalendarService {
@Autowired
private CalendarRepository calendarRepository;
public void create() {
calendarRepository.create(new CalendarItem("TEST"));
}
}
这是我得到的堆栈跟踪的一部分：
java.lang.NullPointerException
at com.skoerkamp.rest.CalendarEndpoint.getCalendarItems(CalendarEndpoint.java:23)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatch
第23行是对calendarService的调用。
抱歉长篇文章，但我想尽可能清楚地表明我的问题。任何意见或建议表示赞赏！在此先感谢：）
答案 0 :(得分：1)
使用Spring，Autowire将始终连接bean，否则它将失败，除非您特别将其标记为@autowired(required = false)如果您获得空指针并且它不是自动装配，则意味着您没有使用Spring来管理您的豆子。
您需要使用Spring MVC（Spring DispatcherServlet）来实例化您的对象。看看http://docs.spring.io/spring/docs/current/spring-framework-reference/html/mvc.html中的17.2。这将向您展示如何配置项目（使用XML或仅使用Annotation），以便Spring管理您的bean并正确地自动装配所有内容。
答案 1 :(得分：0)
为了加载bean并自动装配它们，您需要在web.xml中配置ContextLoaderListener并指定主要上下文的位置，例如“ApplicationContext.xml”，默认情况下为ContextLoaderListener加载以下文件上下文“/WEB-INF/applicationContext.xml”，因此请相应地重命名文件。以下是一些可以帮助您设置和理解上下文加载器机制的链接：
http://www.springbyexample.org/examples/simple-spring-mvc-form-annotation-config-webapp.html#simple-spring-mvc-form-annotation-config-webapp-web-config http://docs.spring.io/spring/docs/current/spring-framework-reference/html/beans.html#context-create
以及解释如何使用Spring 3逐步创建restful api的教程：http://www.ibm.com/developerworks/web/library/wa-spring3webserv/index.html?ca=drs-
答案 2 :(得分：0)
你需要在界面而不是类上使用@Autowired注释。
所以，创建一个接口，让CalendarService类实现它，然后自动装配接口。
希望它有效！