Hibernate表关联对象转Json双向关联解析过度

在做SSH中，遇到了Hibernate 表与表的关联过多，很多双向关联，然后在转Json后，查询内容，查询出很多数据，基本每个表都查询了一次或两次，造成了内存溢出。所以写了一个工具。

package com.gxa.bj.util;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.hibernate.collection.internal.PersistentSet;

public class ConverHelper {
public static Object getCopy(int layer, Object t)
throws ClassNotFoundException, InstantiationException,
IllegalAccessException, NoSuchMethodException, SecurityException,
IllegalArgumentException, InvocationTargetException {
if (t == null)
return null;
if (layer > 0) {
layer--;
} else {
return null;
}
//class内的泛型，得到t的class
Class<?> otClass = (Class<?>) t.getClass();
//查找到此class中实体对象的名字；如com.gxa.bj.model.Dept_$$_jvst6_7 找到的是com.gxa.bj.model.Dept
String ntClassName = otClass.getName().split("_")[0];
@SuppressWarnings("unchecked")
//根据com.gxa.bj.model.Dept找到Dept.class实例
Class ntClass = Class.forName(ntClassName);
//根据Dept.class创建了一个实例
Object newT = ntClass.newInstance();
//找到Dept.class中的属性（注：不会找到父类的属性），getFields()方法找到public中的属性,也会找到父类的属性
Field[] fields = ntClass.getDeclaredFields();
for (Field f : fields) { //反射获取对象拼出get,set方法
String fieldName = f.getName();
String getMethodName = "get"
+ fieldName.substring(0, 1).toUpperCase()
+ fieldName.substring(1);
String setMethodName = "set"
+ fieldName.substring(0, 1).toUpperCase()
+ fieldName.substring(1);
//获取get方法
Method getMethod = otClass.getMethod(getMethodName);
Object obj = getMethod.invoke(t);//获取代理对象中属性的值
if (obj != null) {
System.out.println("转换"+obj);
System.out.println("转换"+obj.getClass());
System.out.println("转换"+ntClass);
//再次查找此class中的实体对象的名字
String objClassName = obj.getClass().getName().split("_")[0];
//查找到实体对象的class实例
Class objClass=Class.forName(objClassName);
//如果查找到的实体对象属于Set类型
if(objClass.isAssignableFrom(PersistentSet.class))
objClass=Set.class;
//如果查找到的实体对象属于Date类型
else if(objClass.isAssignableFrom(Timestamp.class))
objClass=Date.class;
//获取set方法
Method setmethod = ntClass.getMethod(setMethodName,objClass);
//如果获取的是基本类型
if (obj instanceof String || obj instanceof Date
|| obj instanceof Integer) {
setmethod.invoke(newT, obj);//直接使用set赋值
}
//如果属于Set类型就调用getSetCopy方法
else if (obj instanceof Set) {
Set<Object> set = (Set<Object>) obj;
setmethod.invoke(newT, getSetCopy(set, layer));
}
//属于其他类型，也就是代理类型或者model类型使用getCopy方法；
else {
setmethod.invoke(newT, getCopy(layer, obj));
}
}
}
return newT;
}

public static Set<Object> getSetCopy(Set<Object> set, int layer)
throws ClassNotFoundException, InstantiationException,
IllegalAccessException, NoSuchMethodException, SecurityException,
IllegalArgumentException, InvocationTargetException {
if (layer <= 0) {
return null;
}
layer--;
Set<Object> newSet = new HashSet<>();
for (Object obj : set) {
newSet.add(getCopy(layer, obj));
}
return newSet;
}

public static List<Object> getListCopy(List list, int layer)
throws ClassNotFoundException, InstantiationException,
IllegalAccessException, NoSuchMethodException, SecurityException,
IllegalArgumentException, InvocationTargetException {
System.out.
4000
println(list);
if (list == null)
return null;
ArrayList<Object> arrayList = new ArrayList<>();
for (Object obj : list) {
arrayList.add(getCopy(layer, obj));
}
return arrayList;
}
}
在查询的时候，你想调用几层，调用几层。
下面是一个例子：

package com.gxa.bj.action;

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

import com.gxa.bj.model.Dept;
import com.gxa.bj.model.Employees;
import com.gxa.bj.model.Travel;
import com.gxa.bj.service.TravelService;
import com.gxa.bj.util.ConverHelper;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;

public class BseAction extends ActionSupport{
public Map<Object, Object> getMap() {
return map;
}

public void setMap(Map<Object, Object> map) {
this.map = map;
}

private int page;
private int rows;
private Map<Object,Object> map;
public int getPage() {
return page;
}

public void setPage(int page) {
this.page = page;
}

public int getRows() {
return rows;
}

public void setRows(int rows) {
this.rows = rows;
}

public Travel getTravel() {
return travel;
}

public void setTravel(Travel travel) {
this.travel = travel;
}

public TravelService getTravelService() {
return travelService;
}

public void setTravelService(TravelService travelService) {
this.travelService = travelService;
}

public List<Travel> getTravleList() {
return travleList;
}

public void setTravleList(List<Travel> travleList) {
this.travleList = travleList;
}

private Travel travel;
private TravelService travelService;
private List<Travel> travleList;
private String result;

public String getResult() {
return result;
}

public void setResult(String result) {
this.result = result;
}

public String select() throws ClassNotFoundException, NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException{
System.out.println(1);
System.out.println(2);
Travel t =new Travel();
List<Object> list=null;
if((Employees) ActionContext.getContext().getSession().get("login")!=null){
Employees e = (Employees) ActionContext.getContext().getSession().get("login");
System.out.println(e.getUserName());
System.out.println("1110 ++++++0"+e.getDept().getDeptId());
t.setExpense(e);
t.setDeptInfo(e.getDept());
}
travleList=travelService.getList(t,page,rows);

try {
list=ConverHelper.getListCopy(travleList,2);//解析2层
System.out.println(list);
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

Dept dept=travleList.get(0).getDeptInfo();
int a =travelService.getList(t).size();
map=new HashMap<>();
map.put("total", a);
map.put("rows",list);
return SUCCESS;
}
}