Question

我正在从头开始设置一个新项目，以了解配置等。

我总是打电话给我的DAO对象，我在NullPointerException的那一刻得到getEntityManager()。我错过了要实现或配置的东西？也许我的项目无法访问持久性文件？我怎么检查呢？

PROJECT / SRC /主/资源/ META-INF / persistence.xml中

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">

  <persistence-unit name="myUnitPersistent" transaction-type="RESOURCE_LOCAL">  
    <!--  Indicamos que nuestro proveedor de persistencia es Hibernate -->
    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <!-- Propiedades -->
    <properties>
            <!-- Propiedades de JPA -->
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306"/>
            <property name="javax.persistence.jdbc.user" value="root"/>
            <property name="javax.persistence.jdbc.password" value="root"/>

            <!--Hibernate properties-->
            <property name="hibernate.show_sql" value="false"/>
            <property name="hibernate.format_sql" value="false"/>
            <property name="hibernate.hbm2ddl.auto" value="create"/>
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>

    </properties>

  </persistence-unit>
</persistence>

这是我的父项目pom.xml

<dependencies>
        <dependency>
            <groupId>org.hibernate.javax.persistence</groupId>
            <artifactId>hibernate-jpa-2.1-api</artifactId>
            <version>1.0.0.Final</version>
        </dependency>
        <!-- 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>
        <!-- Utils -->
        <dependency>
          <groupId>com.google.guava</groupId>
          <artifactId>guava</artifactId>
          <version>22.0</version>
        </dependency>

        <!-- AspectJ -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>${org.aspectj-version}</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>1.2.15</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>

        <!-- Database Connection -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.6</version>
        </dependency>

        <!-- Test -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.7</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

我的通用DAO：

@Repository
public class DaoBaseImpl<E extends EntityBase> implements DaoBase<E> {

    @PersistenceContext(unitName = "myUnitPersistent")
    private EntityManager entityManager;

    /**
     * Guardamos el tipo de la entidad, nos hará falta para usar el método de manera
     * genérica
     */
    private Class<E> persistentClass;

    /**
     * Devuelve el entityManager, para realizar operaciones sobre la base de datos
     * 
     * @return EntityManger (Gestor de persistencia)
     */
    protected EntityManager getEntityManager() {
        return entityManager;
    }

    //more code
}

Answer 1

添加以下依赖项：

<dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- Spring ORM support -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${spring.version}</version>
        </dependency>

使用SpringMVC + Hibernate，@ PersersContext始终为Null

1 个答案: