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我正在尝试在 Spring 项目中使用 Hibernate 和 JPA，但在注入 EntityManager 时遇到问题。当我部署站点并打开它时，我得到请求处理失败；嵌套异常是 java.lang.NullPointerException 因为管理器始终为空。

这是我的配置文件：

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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.foo</groupId>
    <artifactId>artifact</artifactId>
    <name>name</name>
    <packaging>war</packaging>
    <version>1.0.0-BUILD-SNAPSHOT</version>
    <properties>
        <java-version>1.6</java-version>
        <org.springframework-version>3.2.2.RELEASE</org.springframework-version>
        <org.aspectj-version>1.7.1</org.aspectj-version>
        <org.slf4j-version>1.7.2</org.slf4j-version>
    </properties>
    <dependencies>
        <!-- Spring -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${org.springframework-version}</version>
            <exclusions>
                <!-- Exclude Commons Logging in favor of SLF4j -->
                <exclusion>
                    <groupId>commons-logging</groupId>
                    <artifactId>commons-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <!-- AspectJ -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>${org.aspectj-version}</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-entitymanager</artifactId>
            <version>4.2.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate.javax.persistence</groupId>
            <artifactId>hibernate-jpa-2.0-api</artifactId>
            <version>1.0.1.Final</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>3.2.0.RELEASE</version>
            <!-- will come with all needed Spring dependencies such as spring-core 
                and spring-beans -->
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>4.1.9.Final</version>
            <!-- will come with Hibernate core -->
        </dependency>
        <dependency>
            <groupId>commons-dbcp</groupId>
            <artifactId>commons-dbcp</artifactId>
            <version>20030825.184428</version>
            <type>jar</type>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>commons-pool</groupId>
            <artifactId>commons-pool</artifactId>
            <version>20030825.183949</version>
            <type>jar</type>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>commons-collections</groupId>
            <artifactId>commons-collections</artifactId>
            <version>3.1</version>
        </dependency>


        <!-- Logging -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${org.slf4j-version}</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>jcl-over-slf4j</artifactId>
            <version>${org.slf4j-version}</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>${org.slf4j-version}</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
            <exclusions>
                <exclusion>
                    <groupId>javax.mail</groupId>
                    <artifactId>mail</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>javax.jms</groupId>
                    <artifactId>jms</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>com.sun.jdmk</groupId>
                    <artifactId>jmxtools</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>com.sun.jmx</groupId>
                    <artifactId>jmxri</artifactId>
                </exclusion>
            </exclusions>
            <scope>runtime</scope>
        </dependency>

        <!-- @Inject -->
        <dependency>
            <groupId>javax.inject</groupId>
            <artifactId>javax.inject</artifactId>
            <version>1</version>
        </dependency>

        <!-- Servlet -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

        <!-- Test -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>

        <!-- Validation -->
        <dependency>
            <groupId>javax.validation</groupId>
            <artifactId>validation-api</artifactId>
            <version>1.0.0.GA</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>4.0.0.GA</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>
    <build>
        <finalName>ROOT</finalName>
        <plugins>
            <plugin>
                <artifactId>maven-eclipse-plugin</artifactId>
                <version>2.9</version>
                <configuration>
                    <additionalProjectnatures>
                        <projectnature>org.springframework.ide.eclipse.core.springnature</projectnature>
                    </additionalProjectnatures>
                    <additionalBuildcommands>
                        <buildcommand>org.springframework.ide.eclipse.core.springbuilder</buildcommand>
                    </additionalBuildcommands>
                    <downloadSources>true</downloadSources>
                    <downloadJavadocs>true</downloadJavadocs>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.5.1</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                    <compilerArgument>-Xlint:all</compilerArgument>
                    <showWarnings>true</showWarnings>
                    <showDeprecation>true</showDeprecation>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.2.1</version>
                <configuration>
                    <mainClass>org.test.int1.Main</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

    <display-name>Display name</display-name>

    <!-- The definition of the Root Spring Container shared by all Servlets and Filters -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/spring/root-context.xml</param-value>
    </context-param>

    <!-- Creates the Spring Container shared by all Servlets and Filters -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <!-- Processes application requests -->
    <servlet>
        <servlet-name>appServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/spring/appServlet/servlet-context.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>appServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

根上下文.xml

<?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:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">

    <!-- Root Context: defines shared resources visible to all other web components -->

    <import resource="db.xml" />
</beans>

数据库.xml

<?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:mvc="http://www.springframework.org/schema/mvc"
    xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd  
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd"
    default-autowire="byName">

    <!-- Scans within the base package of the application for @Components to 
        configure as beans -->
    <bean id="placeholderConfig"
        class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="location" value="classpath:db.properties" />
    </bean>

    <bean id="entityManagerFactory"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <property name="showSql" value="true" />
                <property name="generateDdl" value="true" />
                <property name="databasePlatform" value="${db.dialect}" />
            </bean>
        </property>
    </bean>

    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
        destroy-method="close">
        <property name="driverClassName" value="${db.driver}" />
        <property name="url" value="${db.url}" />
        <property name="username" value="${db.username}" />
        <property name="password" value="${db.password}" />
    </bean>

    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory" />
    </bean>

    <tx:annotation-driven transaction-manager="transactionManager"/>

    <bean
        class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />
</beans>

持久性.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
      http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
    version="1.0">

    <persistence-unit name="persistenceUnit" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <properties>
            <property name="hibernate.hbm2ddl.auto" value="create-drop" />
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.transaction.flush_before_completion"
                value="true" />
            <property name="hibernate.cache.provider_class" value="org.hibernate.cache.HashtableCacheProvider" />
        </properties>
    </persistence-unit>
</persistence>

数据库属性

db.password=pass
db.username=user
db.url=jdbc:mysql://url:3306/dbname
db.dialect=org.hibernate.dialect.MySQLInnoDBDialect
db.driver=com.mysql.jdbc.Driver

TagServiceImpl.java

@Repository
@Transactional
public class TagServiceImpl implements TagService {

    @PersistenceContext
    private EntityManager manager;

    @Override
    @Transactional
    public List<Tag> findAll() {
        List <Tag> tags = manager.creationQuery("select t from Tag t").getResultList(); // Exception raised here
        ModelAndView mav = new ModelAndView("tags");
        mav.addObject("tags", tags);

        return tags;
    }
}

标签控制器.java

@Controller
public class TagController {

    /**
     * Simply selects the home view to render by returning its name.
     */
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public ModelAndView home(Locale locale) {
        ModelAndView modelAndView = new ModelAndView("tags");

        TagService tagService = new TagServiceImpl();
        List<Tag> tags = tagService.findAll();

        modelAndView.addObject("tags", tags);

        return modelAndView;
    }
}

我对 Spring 很陌生，但我看不出我做错了什么，所以我希望你能帮助我。我需要更多信息只是问。先感谢您。

4

3 回答 3

2

这必须是此问题的一周，将此添加到您的 Spring Config

<bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />

另请参阅：空指针异常实体管理器

于 2013-04-27T15:29:17.163 回答
0

这是一个视频，将引导您完成所有部分的整个设置：http://pluralsight.com/training/Courses/TableOfContents/spring-jpa-hibernate我的 0.02 美元 我不喜欢从我的服务层返回 ModelAndView 对象. 我注意到一件事，我认为这不是问题，但是您使用的是 JPA 1.0 persistence.xml，但您有 JPA 2.0 jar 和 Hibernate 版本。此外，看起来您也需要一个 context:component-scan 元素。我认为这就是它不扫描您的课程的原因。http://static.springsource.org/spring/docs/3.2.1.RELEASE/spring-framework-reference/html/beans.html#beans-scanning-autodetection

于 2013-04-27T18:44:41.443 回答
0

尝试将 PackageToScan ptoperty 添加到您的 entityManagerFactory 装饰中。

<property name="packagesToScan" value="package.where.your.entities.situated"/>
于 2013-04-29T09:24:06.813 回答