Hibernate用HQL查询

Customer.java

public class Customer {
    
    public Customer() {
        super();
        // TODO Auto-generated constructor stub
    }
    
    public Customer(String cust_name, String cust_source) {
        super();
        this.cust_name = cust_name;
        this.cust_source = cust_source;
    }

    private Long cust_id;
    private String cust_name;
    private String cust_source;
    private String cust_industry;
    private String cust_level;
    private String cust_phone;
    private String cust_mobile;
    //通过 ORM方式表示：一个客户对应的多个联系人
    //防止的多的一方的集合。Hibernate默认使用的是Set集合
    private Set<LinkMan> linkMans=new HashSet<LinkMan>();
    //省略get和set方法
}

LinkMan.java

public class LinkMan {
    private Long lkm_id;
    private String lkm_name;
    private String lkm_gender;
    private String lkm_phone;
    private String lkm_mobile;
    private String lkm_email;
    private String lkm_qq;
    private String lkm_position;
    private String lkm_memo;
    //通过ORM方式表示：一个联系人只能属于一个客户
    //放置的是一的一方的对象
    private Customer customer;
    //省略get和set方法
}

Customer.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.hibernate.domain.Customer" table="cst_customer">
        <!-- 建立OID与主键映射 -->
        <id name="cust_id" column="cust_id">
            <generator class="native"/>
        </id>
        <!-- 建立普通属性和表的字段的对应 -->
        <property name="cust_name" column="cust_name"/>
        <property name="cust_source" column="cust_source"/>
        <property name="cust_industry" column="cust_industry"/>
        <property name="cust_level" column="cust_level"/>
        <property name="cust_phone" column="cust_phone"/>
        <property name="cust_mobile" column="cust_mobile"/>
        <!-- 配置一对多的映射：放置的多的一方的集合 -->
        <!-- 
            set标签
                * name  ：多的一方的对象集合的属性名称
                * cascade:级联
                * inverse:放弃`外键`维护权    默认false:不放弃
         -->
        <set name="linkMans">
            <!-- 
                key标签
                    * column:多的一方的外键的名称
             -->
            <key column="lkm_cust_id"/>
            <!-- 
                one-to-many标签
                    * class :多的一方的全路径
             -->
            <one-to-many class="com.hibernate.domain.LinkMan"/>
        </set>
    </class>
</hibernate-mapping>

LinkMan.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.hibernate.domain.LinkMan" table="cst_linkman">
        <!-- 建立OID与主键映射 -->
        <id name="lkm_id" column="lkm_id">
            <generator class="native"/>
        </id>
        <!-- 建立普通属性与表字段映射 -->
        <property name="lkm_name"/>
        <property name="lkm_gender"/>
        <property name="lkm_phone"/>
        <property name="lkm_mobile"/>
        <property name="lkm_email"/>
        <property name="lkm_qq"/>
        <property name="lkm_position"/>
        <property name="lkm_memo"/>
        <!-- 配置多对一的关系：放置的是一的一方的对象 -->
        <!-- 
            many-to-one标签
                * name      :一的一方的对象的属性名称
                * class     :一的一方的全路径
                * column    ：在多的一方的表的外键的名称
         -->
         <many-to-one name="customer" cascade="save-update,delete" class="com.hibernate.domain.Customer" column="lkm_cust_id"/>
    </class>
</hibernate-mapping>

src下的hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
  "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
  "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <!-- 连接数据库的基本参数 -->
    <!-- hibernate-release-5.0.7.Final\project\etc\hibernate.properties -->
    <!-- localhost:3306 -->
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql:///hibernate_day04</property>
    <property name="hibernate.connection.username">root</property>
    <property name="hibernate.connection.password">password</property>
    <!-- 配置Hibernate的方言 -->
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
    
    <!-- ==========可选配置========= -->
    <!-- 打印sql -->
    <property name="hibernate.show_sql">true</property>
    <!-- 格式化sql -->
    <property name="hibernate.format_sql">true</property>
    <!-- 自动建表create update -->
    <property name="hibernate.hbm2ddl.auto">update</property>
    
    <!-- 设置事务隔离级别 -->
    <!-- 
      1 read uncommitted  :脏读、不可重复读、虚读都会发生
      2 read committed    :解决脏读  (oracle默认)
      4 repeatable read   :解决脏读和不可重复读(mysql默认)
      8 serializable      :解决所有问题。串行执行、效率低
     -->
    <property name="hibernate.connection.isolation">4</property>
    <!-- 配置当前线程绑定的Session -->
    <!-- 不用session.close() -->
    <property name="hibernate.current_session_context_class">thread</property>
    
    <!-- 引入映射 -->
    <mapping resource="com/hibernate/domain/Customer.hbm.xml"/>
    <mapping resource="com/hibernate/domain/LinkMan.hbm.xml"/>
    
  </session-factory>
</hibernate-configuration>

测试类

import java.util.Arrays;
import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.jupiter.api.Test;

import com.hibernate.domain.Customer;
import com.hibernate.domain.LinkMan;
import com.hibernate.utils.HibernateUtils;

/**
 * HQL的查询放置的测试类
 * 
 * @author zhang
 *
 */
public class HibernateDemo1 {

  @Test
  /**
   * 初始化数据
   */
  public void demo1() {
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();

    // 创建一个客户
    Customer customer = new Customer();
    customer.setCust_name("李向文");

    for (int i = 1; i <= 10; i++) {
      LinkMan linkMan = new LinkMan();
      linkMan.setLkm_name("王东" + i);
      linkMan.setCustomer(customer);

      customer.getLinkMans().add(linkMan);
      session.save(linkMan);
    }
    session.save(customer);
    tx.commit();
  }

  @Test
  /**
   * HQL的简单查询
   */
  public void demo2() {
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();
    // 简单的查询
    Query query = session.createQuery("from Customer");
    List<Customer> list = query.list();

    // sql中支持*号的写法：select * from cst_customer;但是HQL中不支持*号的写法
    /*
     * Query query=session.createQuery("select * from cst_customer");//报错
     * List<Customer> list=query.list();
     */

    for (Customer customer : list) {
      System.out.println(customer);
    }
    tx.commit();
  }

  @Test
  /**
   * 别名查询
   */
  public void demo3() {
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();
    // 别名查询
    /*Query query = session.createQuery("from Customer c");
    List<Customer> list = query.list();*/
    
    Query query =session.createQuery("select c from Customer c");
    List<Customer> list = query.list();

    for (Customer customer : list) {
      System.out.println(customer);
    }
    tx.commit();
  }
  
  @Test
  /**
   * 排序查询
   */
  public void demo4() {
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();
    // 排序查询
    //默认情况
//    List<Customer> list= session.createQuery("from Customer order by cust_id").list();
    //设置排序降序 升序asc
    List<Customer> list= session.createQuery("from Customer order by cust_id desc").list();
    for (Customer customer : list) {
      System.out.println(customer);
    }
    tx.commit();
  }
  
  @Test
  /**
   * 条件查询
   */
  public void demo5() {
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();
    // 条件查询
    //一、按位置绑定:根据参数的位置进行绑定
    //一个条件
    /*Query query = session.createQuery("from Customer where cust_name=?");
    query.setParameter(0, "李兵");
    List<Customer> list=query.list();*/
    //多个条件
    /*Query query = session.createQuery("from Customer where cust_name like ? and cust_source=?");
    query.setParameter(0, "李%");
    query.setParameter(1, "计算机");
    List<Customer> list=query.list();*/
    //二、按名称绑定
    Query query = session.createQuery("from Customer where cust_source = :aaa and cust_name like :bbb");
    //设置参数：
    query.setParameter("aaa", "计算机");
    query.setParameter("bbb", "李%");
    List<Customer> list=query.list();
    
    for (Customer customer : list) {
      System.out.println(customer);
    }
    tx.commit();
  }
  
  @Test
  /**
   * 投影查询
   */
  public void demo6() {
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();
    
    //投影查询
    //单个属性
    /*List<Object> list=session.createQuery("select c.cust_name from Customer c").list();
    for (Object object : list) {
      System.out.println(object);
    }*/
    
    //多个属性：
    /*List<Object[]> list=session.createQuery("select c.cust_name,c.cust_source from Customer c").list();
    for (Object[] objects : list) {
      System.out.println(Arrays.toString(objects));
    }*/
    //查询多个属性，但是我想封装到对象中
    List<Customer> list=session.createQuery("select new Customer(cust_name,cust_source) from Customer").list();
    for (Customer customer : list) {
      System.out.println(customer);
    }
    tx.commit();
  }
  
  @Test
  /**
   * 分页查询
   */
  public void demo7() {
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();
    
    //分页查询
    Query query=session.createQuery("from LinkMan");
    query.setFirstResult(10);
    query.setMaxResults(10);
    List<LinkMan> list=query.list();
    
    for (LinkMan linkMan : list) {
      System.out.println(linkMan);
    }
    
    tx.commit();
  }
  
  @Test
  /**
   * 分组统计查询
   */
  public void demo8() {
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();
    
    //聚合函数的使用：count(),max(),min(),avg(),sum()
    /*Object object=session.createQuery("select count(*) from Customer").uniqueResult();//只能查到一个结果
    System.out.println(object);*/
    //分组统计
    List<Object[]> list=session.createQuery("select cust_source,count(*) from Customer group by cust_source").list();
    for (Object[] objects : list) {
      System.out.println(Arrays.toString(objects));
    }
    
    tx.commit();
  }
  
  @Test
  /**
   * HQL的多表查询
   */
  public void demo9() {
    Session session = HibernateUtils.getCurrentSession();
    Transaction tx = session.beginTransaction();
    //SQL:select * from cst_customer c inner join cst_linkman l on c.cust_id=l.lkm_cust_id
    //HQL:内连接from Customer c inner join c.linkMans
    /*List<Object[]> list=session.createQuery("from Customer c inner join c.linkMans").list();
    for (Object[] objects : list) {
      System.out.println(Arrays.toString(objects));
    }*/
    //HQL：迫切内连接  其实就是在普通的内连接inner join后添加一个关键字fetch
    //通知hibernate,将另一个对象的数据封装到该对象中
    List<Customer> list=session.createQuery("select distinct c from Customer c inner join fetch c.linkMans").list();
    for (Customer customer : list) {
      System.out.println(customer);
    }
    tx.commit();
  }
}

感觉HQL是和SQL比较相似的，基本上把表明换成类的属性名，总之还有细微的差别-----------一个当成对象操作映射操作表，另一个直接操作表。