利用Java的反射和JPA写的工具类 博客分类： JavaSE JavaJPASQLHibernateSpring

利用周末时间，花了近4个小时写了个‘万能’的CRUD工具类，不过要使用的话必须是用JPA来进行ORM操作。还有对象映射到数据表中时，Id字段必须是类名称的.LowerCase()+"Id"的形式，不过真的挺方便的。呵呵。水平有限，欢迎指教。

package com.evalution.model;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;


public class CRUDModel {
 
 /**
  * 获取对象列表，参数是要获取的对象的类型，目前是查出数据库的所有该对象的映射记录，
  * 但数据量大的话需要考虑分页等，以及查询的时候可能需要设置一些条件等
  * @param obj
  * @return
  */
 @SuppressWarnings("unchecked")
 public static List getObjectList(Object obj) {
  EntityManagerFactory factory = Persistence.createEntityManagerFactory("evalution");
  EntityManager em = factory.createEntityManager();
  List<Object> list = null;
  String className = obj.getClass().getSimpleName();
  String sql = "SELECT o FROM "+className+" o order by o."+className.toLowerCase()+"Id asc";
  Query query = em.createQuery(sql);
  list = query.getResultList();
  em.close();
  factory.close();
  return list;
 }
 
 /**
  * 保存对象，参数是要保存的对象
  * @param obj
  */
 public static void addObject(Object obj){
  
  EntityManagerFactory factory = Persistence.createEntityManagerFactory("evalution");
  EntityManager em = factory.createEntityManager();
  em.getTransaction().begin();
  em.persist(obj);
  em.getTransaction().commit();
  em.close();
  factory.close();
 }
 
 /**
  * 更新（修改）对象，参数是新对象和原对象的Id。
  * 即根据传入的Id，查处欲修改的对象，并将其修改为新传入的对象
  * @param sourceObj
  * @param id
  * @throws SecurityException
  * @throws IllegalArgumentException
  * @throws NoSuchMethodException
  * @throws IllegalAccessException
  * @throws InvocationTargetException
  */
 public static void updateObject(Object sourceObj, int id) throws SecurityException, IllegalArgumentException, 
  NoSuchMethodException, IllegalAccessException, InvocationTargetException{
  
  EntityManagerFactory factory = Persistence.createEntityManagerFactory("evalution");
  EntityManager em = factory.createEntityManager();
  em.getTransaction().begin();
  Object targetObj = em.find(sourceObj.getClass(), id);
  CRUDModel.copyObjFromSourceToTarget(sourceObj,targetObj);
  em.getTransaction().commit();
  em.close();
  factory.close();
 }
 
 /**
  * 根据传入的对象类型和对象Id获取对象
  * @param obj
  * @param id
  * @return
  */
 public static Object getObjectById(Object obj,int id){
  EntityManagerFactory factory = Persistence.createEntityManagerFactory("evalution");
  EntityManager em = factory.createEntityManager();
  Object object = em.find(obj.getClass(), id);
  em.close();
  factory.close();
  return object;
 }
 
 /**
  * 注意该方法要求对象的主键必须为对象名的小写加Id的形式，即Object.toLowerCase()+"Id"
  * @param obj
  * @param id
  */
 public static void deleteObject(Object obj,int id){
  EntityManagerFactory factory = Persistence.createEntityManagerFactory("evalution");
  EntityManager em = factory.createEntityManager();
  em.getTransaction().begin();
  String className = obj.getClass().getSimpleName();
  Query query = em.createQuery("delete from "+className+" o where o."+className.toLowerCase()+"Id=:id");
  query.setParameter("id", id);
  query.executeUpdate();
  em.getTransaction().commit();
  em.close();
  factory.close();
 }
 
 /**
  * 本方法的功能是将源对象的属性值赋值给目标对象，要求源对象和目标对象是同一类型
  * @param sourceObj
  * @param targetObj
  * @return
  * @throws SecurityException
  * @throws NoSuchMethodException
  * @throws IllegalArgumentException
  * @throws IllegalAccessException
  * @throws InvocationTargetException
  */
 @SuppressWarnings("unchecked")
 public static Object copyObjFromSourceToTarget(Object sourceObj,Object targetObj) throws SecurityException, 
  NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException{
  
  if(!sourceObj.getClass().isInstance(targetObj)){
   System.out.println("两个对象不属同一类型，请核对....");
   return null;
  }
  
  //获取对象的Class，并得到其拥有的方法
  Class targetClass = targetObj.getClass();
  Method [] taregetMethods = targetClass.getDeclaredMethods();
  
  Class sourceClass = sourceObj.getClass();
  
  //遍历方法数组，过滤得到所有Set方法，给目标对象赋值
  for(int i = 0 ;i < taregetMethods.length;i++){
   
   String targetMethodName = taregetMethods[i].getName();
   
   if (targetMethodName.indexOf("set") != -1) {
    
    System.out.println("targetMethodName:"+targetMethodName);
    
    Method method =  targetClass.getMethod(targetMethodName,  taregetMethods[i].getParameterTypes());
    
    Object paramObj = new Object();
    
    //根据目标对象需要赋值的属性，从源对象中通过Get方法获取值
    Method method2 =  sourceClass.getMethod("get"+targetMethodName.substring(3, targetMethodName.length()),null);
    paramObj = method2.invoke(sourceObj, null);
    
    System.out.println("paramObj:"+paramObj);
    
    //将获取的值赋值给目标对象
    method.invoke(targetObj, paramObj);
   }
  }
  return targetObj;
 }
 
 /**
  * 根据传入的对象类型和参数列表以及起始和结束行数，获取结果集
  * @param obj 对象类型
  * @param map 给Sql传入的参数
  * @param start 起始行
  * @param end 结束行
  * @return
  */
 @SuppressWarnings("unchecked")
 public static List getObjectListWithParam(Object obj,HashMap<String, String> map,int start,int end) {
  EntityManagerFactory factory = Persistence.createEntityManagerFactory("evalution");
  EntityManager em = factory.createEntityManager();
  List<Object> list = null;
  String className = obj.getClass().getSimpleName();
  StringBuffer sql = new StringBuffer();
  sql.append("SELECT o FROM "+className+" o where 1=1");
  
  Object[] keySet = map.keySet().toArray();
  for (int i = 0; i < keySet.length; i++) {
   String key = (String)keySet[i];
   String value = (String)map.get(key);
   sql.append(" and o."+key+" = "+value);
  }
  sql.append(" order by o."+className.toLowerCase()+"Id asc");
  
  System.out.println(sql.toString());
  
  Query query = em.createQuery(sql.toString());
  if(start != -1 && end != -1){
   query.setFirstResult(start);
   query.setMaxResults(end);
  }
  list = query.getResultList();
  em.close();
  factory.close();
  return list;
 }
 
 /**
  * 获取总结果集的行数
  * @param obj
  * @return
  */
 public static int getRowCount(Object obj){
  EntityManagerFactory factory = Persistence.createEntityManagerFactory("evalution");
  EntityManager em = factory.createEntityManager();
  String sql = "select count(o) from "+obj.getClass().getSimpleName()+" o";
  Query query = em.createQuery(sql);
  Long count = (Long)query.getSingleResult();;
  em.close();
  factory.close();
  return count.intValue();
 }
 
 /**
  * 根据本地Sql返回执行的结果集
  * @param sql
  * @return
  */
 @SuppressWarnings("unchecked")
 public static List getObjectListWithNativeSql(String sql,Class resultClass){
  EntityManagerFactory factory = Persistence.createEntityManagerFactory("evalution");
  EntityManager em = factory.createEntityManager();
  List list = null;
  Query query = em.createNativeQuery(sql,resultClass);
  list = query.getResultList();
  em.close();
  factory.close();
  return list;
 }

}