Java EntityManager memunculkan NullPointerException

Question

Ketika saya mencoba menjalankan tes Unit untuk kelas DAO ini, saya mendapatkan NullPointerException di pernyataan pengembalian getById. Saya tahu bahwa kelas tidak menginisialisasi EntityManager, tetapi saya tidak mengerti mengapa? - Saya tidak tahu apakah konfigurasi persistence.xml saya salah atau kredensial DB salah.

Saya melihat dua atau lebih utas StackOverflow tetapi kurang beruntung. Saya menggunakan Intellij IDE.

package com.beetlehand.model.dao;

import com.beetlehand.model.AttributeEntity;
import org.apache.commons.lang.StringUtils;

import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.TypedQuery;
import java.util.List;
import java.util.Map;
import java.util.ArrayList;

@Stateless
public class AttributeDao extends AbstractDao<AttributeEntity> {

    @PersistenceContext(unitName = "NewPersistenceUnit")
    protected EntityManager entityManager;

    public AttributeEntity getById(Long id) {
        if(id == null) return null;
        return entityManager.find(AttributeEntity.class, id);
    }

    /*** more code ***/ 
}

File konfigurasi persistensi

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0">

    <persistence-unit name="NewPersistenceUnit">
        <class>com.beetlehand.model.AttributeEntity</class>
        <class>com.beetlehand.model.AttributeValueEntity</class>
        <class>com.beetlehand.model.AuditEntity</class>
        <class>com.beetlehand.model.CategoryEntity</class>
        <class>com.beetlehand.model.CustomerEntity</class>
        <class>com.beetlehand.model.DepartmentEntity</class>
        <class>com.beetlehand.model.OrderDetailEntity</class>
        <class>com.beetlehand.model.OrdersEntity</class>
        <class>com.beetlehand.model.ProductEntity</class>
        <class>com.beetlehand.model.ProductAttributeEntity</class>
        <class>com.beetlehand.model.ProductCategoryEntity</class>
        <class>com.beetlehand.model.ReviewEntity</class>
        <class>com.beetlehand.model.ShippingEntity</class>
        <class>com.beetlehand.model.ShippingRegionEntity</class>
        <class>com.beetlehand.model.ShoppingCartEntity</class>
        <class>com.beetlehand.model.TaxEntity</class>
        <properties>
            <property name="toplink.jdbc.url" value="jdbc:mysql://localhost:3306/beetlehand"/>
            <property name="toplink.jdbc.driver" value="com.mysql.jdbc.Driver"/>
            <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/beetlehand"/>
            <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
            <property name="openjpa.ConnectionURL" value="jdbc:mysql://localhost:3306/beetlehand"/>
            <property name="openjpa.ConnectionDriverName" value="com.mysql.jdbc.Driver"/>
            <property name="eclipselink.jdbc.url" value="jdbc:mysql://localhost:3306/beetlehand"/>
            <property name="eclipselink.jdbc.driver" value="com.mysql.jdbc.Driver"/>

            <property name="hibernate.connection.username" value="username"/>
            <property name="hibernate.connection.password" value="password"/>

        </properties>
    </persistence-unit>
</persistence>

Answer 1

Anda perlu mengejek entityManagermaka Anda perlu melakukan rintisan entityManager.find()seperti yang ditunjukkan di bawah ini.

@Mock // Mocking enitt
private EntityManager entityManager;

public AttributeEntity entity = new AttributeEntity();
// Stubbing for entityManager.find()
Mockito.when(entityManager.find(Mockito.any(AttributeEntity.class), Mockito.any())).thenReturn(entity);