一級快取跟二級快取都只能快取實體物件, 而查詢快取可以快取基本屬性, 同時查詢快取也可以快取實體物件, 但是隻能快取其id

查詢快取的生命週期是: 一旦資料庫表的資料發生修改, 則查詢快取則被清掉了

直接使用Hibernate框架提供的查詢快取即可

第一步: 開啟查詢快取總開關

"hibernate.cfg.xml"配置檔案:

<!-- 手動開啟查詢快取
		 -->
        <property name="hibernate.cache.use_query_cache">true</property>

第二步: 在測試類中具體開啟查詢快取的開關:

測試程式碼:

package com.rl.hiber.test;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;
import org.junit.Test;

import com.rl.hiber.model.User;
import com.rl.hiber.utils.HibernateUtils;

public class TestHibernate6 {
    
    @Test
    public void query1(){
        
        Session session = HibernateUtils.getSession();
        try {
            Query query = session.createQuery("select u.uname from User u where u.userId = 1");
            //開啟查詢快取
            query.setCacheable(true);
            //發出sql
            String name = (String)query.uniqueResult();
            System.out.println(name);
        } finally{
            HibernateUtils.closeSession(session);
        }
        
        Session session2 = HibernateUtils.getSession();
        try {
            Query query = session2.createQuery("select u.uname from User u where u.userId = 1");
            //開啟查詢快取
            query.setCacheable(true);
            //不發出sql
            String name = (String)query.uniqueResult();
            System.out.println(name);
        } finally{
            HibernateUtils.closeResource(session2);
        }
    }
    
    /**
     * 查詢快取支援list方法
     */
    @Test
    public void query2(){
        
        Session session = HibernateUtils.getSession();
        try {
            Query query = session.createQuery("select u.uname from User u");
            //開啟查詢快取
            query.setCacheable(true);
            //發出sql
            List<String> nameList = query.list();
            for(String name: nameList){
                System.out.println(name);
            }
        } finally{
            HibernateUtils.closeSession(session);
        }
        
        Session session2 = HibernateUtils.getSession();
        try {
            Query query = session2.createQuery("select u.uname from User u");
            //開啟查詢快取
            query.setCacheable(true);
            //不發出sql
            List<String> nameList = query.list();
            for(String name: nameList){
                System.out.println(name);
            }
        } finally{
            HibernateUtils.closeResource(session2);
        }
    }
    
    /**
     * 查詢快取不支援iterate方法
     */
    @Test
    public void query3(){
        
        Session session = HibernateUtils.getSession();
        try {
            Query query = session.createQuery("select u.uname from User u");
            //開啟查詢快取
            query.setCacheable(true);
            //發出sql
            Iterator<String> iterator = query.iterate();
            while(iterator.hasNext()){
                String name = iterator.next();
                System.out.println(name);
            }
        } finally{
            HibernateUtils.closeSession(session);
        }
        
        Session session2 = HibernateUtils.getSession();
        try {
            Query query = session2.createQuery("select u.uname from User u");
            //開啟查詢快取
            query.setCacheable(true);
            //發出sql
            Iterator<String> iterator = query.iterate();
            while(iterator.hasNext()){
                String name = iterator.next();
                System.out.println(name);
            }
        } finally{
            HibernateUtils.closeResource(session2);
        }
    }
    
    /**
     * 嚴格來講查詢快取並不支援快取實體物件
     * 能夠快取物件的id
     */
    @Test
    public void query4(){
        
        Session session = HibernateUtils.getSession();
        try {
            Query query = session.createQuery("from User");
            //開啟查詢快取
            query.setCacheable(true);
            //發出一條sql查詢全部
            List<User> userList = query.list();
            for(User user: userList){
                System.out.println(user);
            }
        } finally{
            HibernateUtils.closeSession(session);
        }
        
        Session session2 = HibernateUtils.getSession();
        try {
            Query query = session2.createQuery("from User");
            //開啟查詢快取
            query.setCacheable(true);
            //根據快取進來的id查詢具體每一條資料
            List<User> userList = query.list();
            for(User user: userList){
                System.out.println(user);
            }
        } finally{
            HibernateUtils.closeResource(session2);
        }
    }
    
    /**
     * 結合二級快取的iterate方法
     * 利用iterate在二級快取中查詢物件的全部id的特點
     * 此時結合查詢快取則能起到從快取中讀取資料的功能
     */
    @Test
    public void query5(){
        
        Session session = HibernateUtils.getSession();
        try {
            Query query = session.createQuery("select u from User u");
            //開啟查詢快取
            query.setCacheable(true);
            //發出sql
            Iterator<User> iterator = query.iterate();
            while(iterator.hasNext()){
                //發出根據id來查詢的sql
                User user = iterator.next();
                System.out.println(user);
            }
        } finally{
            HibernateUtils.closeSession(session);
        }
        
        Session session2 = HibernateUtils.getSession();
        try {
            Query query = session2.createQuery("select u from User u");
            //開啟查詢快取
            query.setCacheable(true);
            //發出sql查詢出所有的id
            Iterator<User> iterator = query.iterate();
            while(iterator.hasNext()){
                //不發出sql
                User user = iterator.next();
                System.out.println(user);
            }
        } finally{
            HibernateUtils.closeResource(session2);
        }
    }
}