标签：des c style class blog code
概述
HQL 检索方式
HQL(Hibernate Query Language) 是面向对象的查询语言, 它和 SQL 查询语言有些相似. 在 Hibernate 提供的各种检索方式中, HQL 是使用最广的一种检索方式. 它有如下功能:
HQL 检索方式包括以下步骤:
Qurey 接口支持方法链编程风格, 它的 setXxx() 方法返回自身实例, 而不是 void 类型
HQL vs SQL:
绑定参数:
分页查询:
HQL (迫切)内连接
关联级别运行时的检索策略
实例详解：
Department.java
package com.atguigu.hibernate.entities;
import java.util.HashSet;
import java.util.Set;
public class Department {
private Integer id;
private String name;
private Set<Employee> emps = new HashSet<>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<Employee> getEmps() {
return emps;
}
public void setEmps(Set<Employee> emps) {
this.emps = emps;
}
@Override
public String toString() {
return "Department [id=" + id + "]";
}
}
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.atguigu.hibernate.entities.Department" table="GG_DEPARTMENT">
<id name="id" type="java.lang.Integer">
<column name="ID" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="NAME" />
</property>
<set name="emps" table="GG_EMPLOYEE" inverse="true" lazy="true">
<key>
<column name="DEPT_ID" />
</key>
<one-to-many class="com.atguigu.hibernate.entities.Employee" />
</set>
</class>
</hibernate-mapping>
package com.atguigu.hibernate.entities;
public class Employee {
private Integer id;
private String name;
private float salary;
private String email;
private Department dept;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getSalary() {
return salary;
}
public void setSalary(float salary) {
this.salary = salary;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public Department getDept() {
return dept;
}
public void setDept(Department dept) {
this.dept = dept;
}
@Override
public String toString() {
return "Employee [id=" + id + "]";
}
public Employee(String email, float salary, Department dept) {
super();
this.salary = salary;
this.email = email;
this.dept = dept;
}
public Employee() {
// TODO Auto-generated constructor stub
}
}
Employee.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.atguigu.hibernate.entities.Employee" table="GG_EMPLOYEE">
<!--
<cache usage="read-write"/>
-->
<id name="id" type="java.lang.Integer">
<column name="ID" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="NAME" />
</property>
<property name="salary" type="float">
<column name="SALARY" />
</property>
<property name="email" type="java.lang.String">
<column name="EMAIL" />
</property>
<many-to-one name="dept" class="com.atguigu.hibernate.entities.Department">
<column name="DEPT_ID" />
</many-to-one>
</class>
<query name="salaryEmps"><![CDATA[FROM Employee e WHERE e.salary > :minSal AND e.salary < :maxSal]]></query>
</hibernate-mapping>
package com.atguigu.hibernate.test;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Conjunction;
import org.hibernate.criterion.Disjunction;
import org.hibernate.criterion.MatchMode;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;
import org.hibernate.jdbc.Work;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.atguigu.hibernate.dao.DepartmentDao;
import com.atguigu.hibernate.entities.Department;
import com.atguigu.hibernate.entities.Employee;
import com.atguigu.hibernate.hibernate.HibernateUtils;
public class HibernateTest {
private SessionFactory sessionFactory;
private Session session;
private Transaction transaction;
@Before
public void init(){
Configuration configuration = new Configuration().configure();
ServiceRegistry serviceRegistry =
new ServiceRegistryBuilder().applySettings(configuration.getProperties())
.buildServiceRegistry();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
session = sessionFactory.openSession();
transaction = session.beginTransaction();
}
@After
public void destroy(){
transaction.commit();
session.close();
sessionFactory.close();
}
@Test
public void testBatch(){
session.doWork(new Work() {
@Override
public void execute(Connection connection) throws SQLException {
//通过 JDBC 原生的 API 进行操作, 效率最高, 速度最快!
}
});
}
@Test
public void testHQLUpdate(){
String hql = "DELETE FROM Department d WHERE d.id = :id";
session.createQuery(hql).setInteger("id", 280)
.executeUpdate();
}
@Test
public void testNativeSQL(){
String sql = "INSERT INTO gg_department VALUES(?, ?)";
Query query = session.createSQLQuery(sql);
query.setInteger(0, 280)
.setString(1, "ATGUIGU")
.executeUpdate();
}
@Test
public void testQBC4(){
Criteria criteria = session.createCriteria(Employee.class);
//1. 添加排序
criteria.addOrder(Order.asc("salary"));
criteria.addOrder(Order.desc("email"));
//2. 添加翻页方法
int pageSize = 5;
int pageNo = 3;
criteria.setFirstResult((pageNo - 1) * pageSize)
.setMaxResults(pageSize)
.list();
}
@Test
public void testQBC3(){
Criteria criteria = session.createCriteria(Employee.class);
//统计查询: 使用 Projection 来表示: 可以由 Projections 的静态方法得到
criteria.setProjection(Projections.max("salary"));
System.out.println(criteria.uniqueResult());
}
@Test
public void testQBC2(){
Criteria criteria = session.createCriteria(Employee.class);
//1. AND: 使用 Conjunction 表示
//Conjunction 本身就是一个 Criterion 对象
//且其中还可以添加 Criterion 对象
Conjunction conjunction = Restrictions.conjunction();
conjunction.add(Restrictions.like("name", "a", MatchMode.ANYWHERE));
Department dept = new Department();
dept.setId(80);
conjunction.add(Restrictions.eq("dept", dept));
System.out.println(conjunction);
//2. OR
Disjunction disjunction = Restrictions.disjunction();
disjunction.add(Restrictions.ge("salary", 6000F));
disjunction.add(Restrictions.isNull("email"));
criteria.add(disjunction);
criteria.add(conjunction);
criteria.list();
}
@Test
public void testQBC(){
//1. 创建一个 Criteria 对象
Criteria criteria = session.createCriteria(Employee.class);
//2. 添加查询条件: 在 QBC 中查询条件使用 Criterion 来表示
//Criterion 可以通过 Restrictions 的静态方法得到
criteria.add(Restrictions.eq("email", "SKUMAR"));
criteria.add(Restrictions.gt("salary", 5000F));
//3. 执行查询
Employee employee = (Employee) criteria.uniqueResult();
System.out.println(employee);
}
@Test
public void testLeftJoinFetch2(){
String hql = "SELECT e FROM Employee e INNER JOIN e.dept";
Query query = session.createQuery(hql);
List<Employee> emps = query.list();
System.out.println(emps.size());
for(Employee emp: emps){
System.out.println(emp.getName() + ", " + emp.getDept().getName());
}
}
@Test
public void testLeftJoin(){
String hql = "SELECT DISTINCT d FROM Department d LEFT JOIN d.emps";
Query query = session.createQuery(hql);
List<Department> depts = query.list();
System.out.println(depts.size());
for(Department dept: depts){
System.out.println(dept.getName() + ", " + dept.getEmps().size());
}
// List<Object []> result = query.list();
// result = new ArrayList<>(new LinkedHashSet<>(result));
// System.out.println(result);
//
// for(Object [] objs: result){
// System.out.println(Arrays.asList(objs));
// }
}
@Test
public void testLeftJoinFetch(){
// String hql = "SELECT DISTINCT d FROM Department d LEFT JOIN FETCH d.emps";
String hql = "FROM Department d INNER JOIN FETCH d.emps";
Query query = session.createQuery(hql);
List<Department> depts = query.list();
depts = new ArrayList<>(new LinkedHashSet(depts));
System.out.println(depts.size());
for(Department dept: depts){
System.out.println(dept.getName() + "-" + dept.getEmps().size());
}
}
@Test
public void testGroupBy(){
String hql = "SELECT min(e.salary), max(e.salary) "
+ "FROM Employee e "
+ "GROUP BY e.dept "
+ "HAVING min(salary) > :minSal";
Query query = session.createQuery(hql)
.setFloat("minSal", 8000);
List<Object []> result = query.list();
for(Object [] objs: result){
System.out.println(Arrays.asList(objs));
}
}
@Test
public void testFieldQuery2(){
String hql = "SELECT new Employee(e.email, e.salary, e.dept) "
+ "FROM Employee e "
+ "WHERE e.dept = :dept";
Query query = session.createQuery(hql);
Department dept = new Department();
dept.setId(80);
List<Employee> result = query.setEntity("dept", dept)
.list();
for(Employee emp: result){
System.out.println(emp.getId() + ", " + emp.getEmail()
+ ", " + emp.getSalary() + ", " + emp.getDept());
}
}
@Test
public void testFieldQuery(){
String hql = "SELECT e.email, e.salary, e.dept FROM Employee e WHERE e.dept = :dept";
Query query = session.createQuery(hql);
Department dept = new Department();
dept.setId(80);
List<Object[]> result = query.setEntity("dept", dept)
.list();
for(Object [] objs: result){
System.out.println(Arrays.asList(objs));
}
}
@Test
public void testNamedQuery(){
Query query = session.getNamedQuery("salaryEmps");
List<Employee> emps = query.setFloat("minSal", 5000)
.setFloat("maxSal", 10000)
.list();
System.out.println(emps.size());
}
@Test
public void testPageQuery(){
String hql = "FROM Employee";
Query query = session.createQuery(hql);
int pageNo = 22;
int pageSize = 5;
List<Employee> emps =
query.setFirstResult((pageNo - 1) * pageSize)
.setMaxResults(pageSize)
.list();
System.out.println(emps);
}
@Test
public void testHQLNamedParameter(){
//1. 创建 Query 对象
//基于命名参数.
String hql = "FROM Employee e WHERE e.salary > :sal AND e.email LIKE :email";
Query query = session.createQuery(hql);
//2. 绑定参数
query.setFloat("sal", 7000)
.setString("email", "%A%");
//3. 执行查询
List<Employee> emps = query.list();
System.out.println(emps.size());
}
@Test
public void testHQL(){
//1. 创建 Query 对象
//基于位置的参数.
String hql = "FROM Employee e WHERE e.salary > ? AND e.email LIKE ? AND e.dept = ? "
+ "ORDER BY e.salary";
Query query = session.createQuery(hql);
//2. 绑定参数
//Query 对象调用 setXxx 方法支持方法链的编程风格.
Department dept = new Department();
dept.setId(80);
query.setFloat(0, 6000)
.setString(1, "%A%")
.setEntity(2, dept);
//3. 执行查询
List<Employee> emps = query.list();
System.out.println(emps.size());
}
}
标签：des c style class blog code
原文地址：http://blog.csdn.net/qilixiang012/article/details/27979537
