Hibernate查询 load与get的差异及其它查询测试
Hibernate查询 load与get的区别及其它查询测试
一、测试load与get
默认配置下，load将实现懒加载，即只有当对象被使用的时候才发出sql，而get将立刻发出sql
如下：
POJO：
package com.lwf.hibernate;
import java.util.Date;
public class Doc {
private String id;
private String name;
private Date createDate;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getCreateDate() {
return createDate;
}
public void setCreateDate(Date createDate) {
this.createDate = createDate;
}
}
配置文件：
<?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.lwf.hibernate.Doc"> <id name="id"> <generator class="uuid"></generator> </id> <property name="name"></property> <property name="createDate"></property> </class> <query name="HqlName"> <![CDATA[select id,name from Doc]]> </query> <query name="HqlNameAll"> <![CDATA[from Doc order by name desc]]> </query> <query name="HqlNameAllParam"> <![CDATA[from Doc where name=:name]]> </query> </hibernate-mapping>
测试代码：
package com.lwf.hibernate;
import java.util.Date;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class DocSessionTest {
public static void main(String[] args) {
// testSave();
testGet();
//testLoad();
}
public static void commit(Session session){
try {
session.getTransaction().commit();
} catch (HibernateException e) {
e.printStackTrace();
session.getTransaction().rollback();
}
}
public static void closeSession(Session session){
if(session.isOpen()){
session.close();
}
}
public static Session getSession(){
Session session = null;
Configuration config = new Configuration().configure();
SessionFactory factory = config.buildSessionFactory();
session = factory.openSession();
return session;
}
public static void testSave(){
Session session = null;
session = getSession();
session.beginTransaction();
Doc doc = new Doc();
session.save(doc);
doc.setName("gdgdgd");
doc.setCreateDate(new Date());
session.flush();
commit(session);
closeSession(session);
}
public static void testGet(){
Session session = null;
session = getSession();
session.beginTransaction();
Doc doc = (Doc)session.get(Doc.class, "402880f62861314e0128613157060001");
//get会立刻发出查询语句,而load则不会立刻发出查询,直到后面有使用doc如doc.setName才进行查询.
//System.out.println(doc.getName());
//doc.setName("t");
session.flush();
commit(session);
closeSession(session);
}
public static void testLoad(){
Session session = null;
session = getSession();
session.beginTransaction();
//get会立刻发出查询语句,而load则不会立刻发出查询,直到后面有使用doc如doc.setName才进行查询.
//load方法实现了lazy即懒模式
Doc doc =(Doc)session.load(Doc.class, "40288e81280b1db101280b1db61c0001");
//System.out.println(doc.getName());
//doc.setName("t");
session.flush();
commit(session);
closeSession(session);
}
}
运行代码会发现load与get的不同。
另外，如果没有查询到数据，get会返回null，而load回返回异常
二、下例中对HQL的各种情况的查询，删除进行演示
package com.lwf.hibernate;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class DocSqlTest {
public static void main(String[] args) {
Configuration cfg = new Configuration().configure();
SessionFactory factory = cfg.buildSessionFactory();
Session session = factory.openSession();
session.beginTransaction();
//where子句中使用值传递
String sqlStr = "from Doc where name ='we'";
getDocList(session,sqlStr);
//where子句中使用参数传递，参数通过query.setString(paramName,paramVal);设置
sqlStr = "from Doc where name =:name";
Object[] object = new Object[2];
object[1] = "yeeey";
getDocList(session,sqlStr,object);
//where子句中使用参数传递，参数通过query.setProperties(object);设置
sqlStr = "from Doc where name =:name";
Doc doc = new Doc();
doc.setName("Lisi1");
getDocList(session,sqlStr,doc);
//通过sqlStr字符串设定的查询条件进行查询
sqlStr = "select id,name from Doc";
getDocObject(session,sqlStr);
//通过从配置文件中获得查询语句进行查询
getDocBynameQuery(session);
//get getObjectBynameQuery
getObjectBynameQuery(session);
//get getDocBynameQueryParam
getDocBynameQueryParam(session);
//只获得一笔记录
sqlStr = "from Doc";
getSingleData(session,sqlStr);
//通过改变查询条件进行查询。
sqlStr = "from Doc where lower(name)='df'";
getDocList(session,sqlStr);
sqlStr = "from Doc where name not in ('we','df')";
getDocList(session,sqlStr);
sqlStr = "from Doc where name like '_e%'";
getDocList(session,sqlStr);
//获得总记录数
sqlStr = "select count(*) from Doc";
Long l = (Long)session.createQuery(sqlStr).uniqueResult();
System.out.println(l);
//测试group by子名
sqlStr = "select name from Doc group by name having name is not null";
getDocName(session,sqlStr);
session.getTransaction().commit();
session.flush();
if(session.isOpen()){
session.close();
}
//测试删除表记录
session = factory.openSession();
session.beginTransaction();
Query query = session.createQuery("delete from Doc");
query.executeUpdate();
session.getTransaction().commit();
if(session.isOpen()){
session.close();
}
}
public static void getSingleData(Session session,String sqlStr){
Query query = session.createQuery(sqlStr);
query.setFirstResult(0);
query.setMaxResults(1);
Object object = query.uniqueResult();
System.out.println(((Doc)object).getId() + " : " + ((Doc)object).getName());
}
public static void getDocBynameQueryParam(Session session){
Query query = session.getNamedQuery("HqlNameAllParam");
query.setString("name", "we");
List list = query.list();
for (int i = 0; i < list.size(); i++) {
Doc doc = (Doc)list.get(i);
String id = doc.getId();
String name = doc.getName();
System.out.println(id +" : "+ name);
}
}
public static void getDocBynameQuery(Session session){
Query query = session.getNamedQuery("HqlNameAll");
List list = query.list();
for (int i = 0; i < list.size(); i++) {
Doc doc = (Doc)list.get(i);
String id = doc.getId();
String name = doc.getName();
System.out.println(id +" : "+ name);
}
}
public static void getObjectBynameQuery(Session session){
Query query = session.getNamedQuery("HqlName");
List list = query.list();
for (int i = 0; i < list.size(); i++) {
Object[] object = (Object[])list.get(i);
System.out.println(object[0] + " <:> " + object[1]);
}
}
public static void getDocList(Session session,String sqlStr,Object object){
Query query = session.createQuery(sqlStr);
query.setProperties(object);
List list = query.list();
for (int i = 0; i < list.size(); i++) {
Doc doc = (Doc)list.get(i);
String id = doc.getId();
String name = doc.getName();
System.out.println(id +" : "+ name);
}
}
public static void getDocList(Session session,String sqlStr, Object[] parameter){
Query query = session.createQuery(sqlStr);
query.setString("name", (String)parameter[1]);
List list = query.list();
for (int i = 0; i < list.size(); i++) {
Doc doc = (Doc)list.get(i);
String id = doc.getId();
String name = doc.getName();
System.out.println(id +" : "+ name);
}
}
public static void getDocList(Session session,String sqlStr){
Query query = session.createQuery(sqlStr);
List list = query.list();
for (int i = 0; i < list.size(); i++) {
Doc doc = (Doc)list.get(i);
String id = doc.getId();
String name = doc.getName();
System.out.println(id +" : "+ name);
}
}
public static void getDocObject(Session session,String sqlStr){
Query query = session.createQuery(sqlStr);
List list = query.list();
for (int i = 0; i < list.size(); i++) {
Object[] object = (Object[])list.get(i);
System.out.println(object[0] + " <:> " + object[1]);
}
}
public static void getDocName(Session session,String sqlStr){
Query query = session.createQuery(sqlStr);
List list = query.list();
for (int i = 0; i < list.size(); i++) {
String name = (String)list.get(i);
System.out.println(name);
}
}
}