JavaEE(17) - JPA查询API和JPQL

1. 获取查询结果

2. JPQL函数和JPQL表达式

#1. 使用from子句

#2. 查询部分属性

#3. 查询中使用构造器

3. JPQL的关联查询和多态查询

#1. 多态查询

#2. 隐式连接

#3. 显式连接

4. 对查询结果集进行分页

5. 使用JPQL子查询和命名查询

#1. 子查询

#2. 命名查询

6. JPQL的批量更新和删除

#1. 批量更新

#2. 批量删除

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1. 获取查询结果(Net Beans创建Java Project, 项目名称:JpqlQs)

JpaQs.java

package lee;

import java.util.List;
import javax.persistence.*;

import org.crazyit.model.*;

public class JpaQs {

    private static final EntityManagerFactory emf = Persistence.createEntityManagerFactory("qs");

    public static void main(String[] args) {
        EntityManager em = emf.createEntityManager();
        try {
            em.getTransaction().begin();
            Query query = em.createQuery("select news , news.title , news.content"
                    + " from News as news where news.id > ?1 and"
                    + " news.title not like :title");

            List result = query.setParameter(1, 1).setParameter("title", "%Java%").getResultList();
            for (int i = 0; i < result.size(); i++) {
                Object[] row = (Object[]) result.get(i);
                for (int j = 0; j < row.length; j++) {
                    System.out.println(row[j]);
                }
            }
            em.getTransaction().commit();
        }
        finally {
            em.close();
        }
    }
}

News.java(参见12.2)

persistence.xml(参见12.2)

2. JPQL函数和JPQL表达式

#1. 使用from子句(Net Beans创建Java Project, 项目名称:From)

JpaQs.java

package lee;

import java.util.List;
import javax.persistence.*;

import org.crazyit.model.*;

public class JpaQs {

    private static final EntityManagerFactory emf = Persistence.createEntityManagerFactory("qs");

    public static void main(String[] args) {
        EntityManager em = emf.createEntityManager();
        try {
            em.getTransaction().begin();
            Query query = em.createQuery("from News as news where news.id < ?1"
                    + " and news.title like :title");

            List result = query.setParameter(1, 8).setParameter("title", "%Java%").getResultList();

            for (int i = 0; i < result.size(); i++) {
                News news = (News) result.get(i);
                System.out.println(news.getTitle() + "-->" + news.getContent());
            }

            em.getTransaction().commit();
        }
        finally {
            em.close();
        }
    }
}

News.java(参见12.2)

persistence.xml(参见12.2)

#2. 查询部分属性(Net Beans创建Java Project, 项目名称:SubProperty)

JpaQs.java

package lee;

import java.util.List;
import javax.persistence.*;

import org.crazyit.model.*;

public class JpaQs {

    private static final EntityManagerFactory emf = Persistence.createEntityManagerFactory("qs");

    public static void main(String[] args) {
        EntityManager em = emf.createEntityManager();
        try {

            em.getTransaction().begin();
            Query query = em.createQuery("select news.title , news.content"
                    + " from News as news where news.id < ?1"
                    + " and news.title like :title");

            List result = query.setParameter(1, 8).setParameter("title", "%Java%").getResultList();
            for (int i = 0; i < result.size(); i++) {
                Object[] values = (Object[]) result.get(i);
                System.out.println(values[0] + "-->" + values[1]);
            }

            em.getTransaction().commit();
        }
        finally {
            em.close();
        }
    }
}

News.java(参见12.2)

persistence.xml(参见12.2)

#3. 查询中使用构造器(Net Beans创建Java Project, 项目名称:Constructor)

NewsDTO.java

package org.crazyit.dto;

public class NewsDTO {

    private String title;
    private String content;

    // constructor

    // setter
    // getter
}

JpaQs.java

package lee;

import java.util.List;
import javax.persistence.*;

import org.crazyit.model.*;

public class JpaQs {

    private static final EntityManagerFactory emf = Persistence.createEntityManagerFactory("qs");
    public static void main(String[] args) {
        EntityManager em = emf.createEntityManager();
        try {
            em.getTransaction().begin();
            Query query = em.createQuery("select distinct new org.crazyit.dto.NewsDTO(news.title"
                + " , news.content) from News as news where news.id < ?1"
                + " and news.title like :title");

            List result = query.setParameter(1, 8).setParameter("title", "%Java%").getResultList();
            for (int i = 0; i < result.size(); i++) {
                System.out.println(result.get(i));
            }

            em.getTransaction().commit();
        }
        finally {
            em.close();
        }
    }
}

News.java(参见12.2)

persistence.xml(参见12.2)

3. JPQL的关联查询和多态查询

#1. 多态查询(Net Beans创建Java Project, 项目名称:PolyQuery)

News.java(参见12.2)

persistence.xml(参见12.2)

#2. 隐式连接(Net Beans创建Java Project, 项目名称:ImplicitJoin)

News.java(参见12.2)

persistence.xml(参见12.2)

#3. 显式连接(Net Beans创建Java Project, 项目名称:ExplicitJoin)

News.java(参见12.2)

persistence.xml(参见12.2)

4. 对查询结果集进行分页(Net Beans创建Java Project, 项目名称:Paging)

News.java(参见12.2)

persistence.xml(参见12.2)

5. 使用JPQL子查询和命名查询

#1. 子查询(Net Beans创建Java Project, 项目名称:SubQuery)

News.java(参见12.2)

persistence.xml(参见12.2)

#2. 命名查询(Net Beans创建Java Project, 项目名称:NamedQuery)

News.java(参见12.2)

persistence.xml(参见12.2)

6. JPQL的批量更新和删除

#1. 批量更新(Net Beans创建Java Project, 项目名称:Update)

News.java(参见12.2)

persistence.xml(参见12.2)

#2. 批量删除(Net Beans创建Java Project, 项目名称:Delete)

News.java(参见12.2)

persistence.xml(参见12.2)