spring + hibernate + jetty进入实体管理器时出现空指针异常

Question

一旦hibernate的实体管理器尝试创建查询，我就会得到一个空指针异常。当我尝试调试时，它就不是null（它有一个上下文）。

以下是我得到的确切例外

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:808)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:587)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:577)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:215)
    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:110)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:499)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
    at java.lang.Thread.run(Thread.java:745)
Caused by: 
java.lang.NullPointerException
    at org.jboss.resteasy.core.ExceptionHandler.executeExactExceptionMapper(ExceptionHandler.java:52)
    at org.jboss.resteasy.core.ExceptionHandler.handleException(ExceptionHandler.java:208)
    at org.jboss.resteasy.core.SynchronousDispatcher.writeException(SynchronousDispatcher.java:149)
    at org.jboss.resteasy.springmvc.ResteasyNoResourceFoundView$1.handle(ResteasyNoResourceFoundView.java:43)
    at org.jboss.resteasy.springmvc.ResteasyNoResourceFoundView$1.handle(ResteasyNoResourceFoundView.java:38)
    at org.jboss.resteasy.springmvc.ResteasyWebHandlerTemplate.handle(ResteasyWebHandlerTemplate.java:39)
    at org.jboss.resteasy.springmvc.ResteasyNoResourceFoundView.render(ResteasyNoResourceFoundView.java:37)
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1244)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1027)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:971)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:808)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:587)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:577)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:215)
    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:110)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:499)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
    at java.lang.Thread.run(Thread.java:745)

以下是 persistence-config.xml 。这是在应用程序上下文中导入的

<?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"

    xmlns:aop="http://www.springframework.org/schema/aop" 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/context http://www.springframework.org/schema/context/spring-context-4.0.xsd

       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd

       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">

    <bean id="entityManagerFactory"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="persistenceXmlLocation" value="classpath:META-INF/persistence.xml"/>
            <property name="persistenceUnitName" value="aspu" />
            <property name="dataSource" ref="dataSource" />
            <property name="jpaVendorAdapter" ref="jpaVendorAdapter" />
            <property name="jpaDialect" ref="jpaDialect" />
            </bean>

    <bean id="jpaVendorAdapter"
        class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
        <property name="database" value="HSQL" />
        <property name="databasePlatform" value="org.hibernate.dialect.HSQLDialect" />
    </bean>

    <bean id="jpaDialect" class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />

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

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

    <bean id="dataSource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost:3306/ASDB" />
        <property name="username" value="root" />
        <property name="password" value="root@123" />
    </bean>
    </beans>

的persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
    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_2_0.xsd">
     <persistence-unit name="aspu" transaction-type="RESOURCE_LOCAL">
         <class>main.java.com.as.entity.MobileAppEntity</class>
         <properties>
       <property name="hibernate.show_sql" value="true"></property>
       </properties>
        </persistence-unit>
   </persistence>

DAO impl class

package main.java.com.as.dao;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import main.java.com.as.entity.MobileAppEntity;
import org.springframework.stereotype.Component;
import org.springframework.transaction.annotation.Transactional;

@Component
public class ASDAOImpl implements ASDao {

    @PersistenceContext(unitName="aspu")
    private EntityManager entityManager;
    @Override
    @Transactional
    public boolean validateCapping(String loyaltyId, int capLimit) {
        String query = "select processId from MobileAppEntity;";
        String cappingCount = entityManager.createQuery(query).getResultList().toString();
        if (Integer.parseInt(cappingCount) > capLimit)
            return false;
        return true;

    }

我在entityManager.createQuery(query).getResultList().toString();

收到了上述异常

Answer 1

您使用mysql作为数据库但是为HSQL DB定义了jpaVendorAdapter bean

<bean id="jpaVendorAdapter"
        class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
        <property name="database" value="HSQL" />
        <property name="databasePlatform" value="org.hibernate.dialect.HSQLDialect" />
</bean>

更改为

<bean id="jpaVendorAdapter"
        class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
        <property name="databasePlatform" value="org.hibernate.dialect.MySQL5Dialect"/>
</bean>

添加JpaVendorAdapter Provider，以便通过以下方式替换persistance.xml中的所有代码：

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
    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_2_0.xsd">
     <persistence-unit name="aspu" transaction-type="RESOURCE_LOCAL">
         <provider>org.hibernate.ejb.HibernatePersistence</provider>
         <class>main.java.com.as.entity.MobileAppEntity</class>
         <properties>
       <property name="hibernate.show_sql" value="true"></property>
       </properties>
        </persistence-unit>
   </persistence>

最后： 修改方法如下：

public boolean validateCapping(String loyaltyId, int capLimit) {
       /*
          Remove semicolon and get single result for one object from result set
          Check result value is null or not before parsing otherwise thows NPE
       */
        String query = "select m.processId from MobileAppEntity m";
        String cappingCount = entityManager.createQuery(query).getSingleResult();

        if (cappingCount != null && Integer.parseInt(cappingCount) > capLimit)
            return false;
        return true;

    }

注意：如果您尝试解析cappingCount的空值，那么在将String解析为Integer之前，未经检查的空指针异常不为空

Answer 2

分号不正确。从查询字符串中删除它