自己编写的一个Json工具类，实现了反射将整个Object转换为Json对象的功能，支持Hibernate的延迟加载对象
由于Json自己的String转换有问题，无法正确的转换中文为uxxxx的字符，因此改用DWR包内的JavascriptUtil处理 String类型。可以直接引用，还可以拆离出来，因为仅是一个转换工具类，跟DWR的没有依赖关系。这样就可以采用ISO-8859-1编码来传递所有 UNICODE了。
代码：
package com.aherp.framework.util;import java.lang.reflect.Array;import java.lang.reflect.Method;import java.util.Collection;import java.util.Iterator;import java.util.Map;import org.json.JSONArray;import org.json.JSONException;import org.json.JSONObject;import org.json.JSONString;
/**
* JSON工具类，反射的方式转换整个对象 * @author Jim Wu *
*/public class JSONUtil { private static JSONUtil instance = null; 
public JSONUtil(){}
/** * 代理类时做的检查.返回应该检查的对象. * @param bean * @return
*/ protected Object proxyCheck(Object bean){ return bean; } static public String toJSONString(Object obj) throws JSONException{ return toJSONString(obj, false); } static public String toJSONString(Object obj, boolean useClassConvert) throws JSONException{ if(instance == null) instance = new JSONUtil(); return instance.getJSONObject(obj, useClassConvert).toString(); } private String getJSONArray(Object arrayObj, boolean useClassConvert) throws JSONException{ if(arrayObj == null) return "null"; arrayObj = proxyCheck(arrayObj); JSONArray jSONArray = new JSONArray(); if(arrayObj instanceof Collection){ Iterator iterator = ((Collection)arrayObj).iterator(); while(iterator.hasNext()){ Object rowObj = iterator.next(); if(rowObj == null) jSONArray.put(new JSONStringObject(null)); else if(rowObj.getClass().isArray() || rowObj instanceof Collection) jSONArray.put(getJSONArray(rowObj, useClassConvert)); else jSONArray.put(getJSONObject(rowObj, useClassConvert)); } } if(arrayObj.getClass().isArray()){ int arrayLength = Array.getLength(arrayObj); for(int i = 0; i < arrayLength; i ++){ Object rowObj = Array.get(arrayObj, i); if(rowObj == null) jSONArray.put(new JSONStringObject(null)); else if(rowObj.getClass().isArray() || rowObj instanceof Collection) jSONArray.put(getJSONArray(rowObj, useClassConvert)); else jSONArray.put(getJSONObject(rowObj, useClassConvert)); } } return jSONArray.toString(); } JSONStringObject getJSONObject(Object value, boolean useClassConvert) throws JSONException{ //处理原始类型 if (value == null) { return new JSONStringObject("null"); } value = proxyCheck(value); if (value instanceof JSONString) { Object o; try { o = ((JSONString)value).toJSONString(); } catch (Exception e) { throw new JSONException(e); } throw new JSONException("Bad value from toJSONString: " + o); } if (value instanceof Number) { return new JSONStringObject(JSONObject.numberToString((Number) value)); } if (value instanceof Boolean || value instanceof JSONObject || value instanceof JSONArray) { return new JSONStringObject(value.toString()); } if (value instanceof String) return new JSONStringObject('"' + JavascriptUtil.escapeJavaScript(value.toString()) + '"'); if (value instanceof Map) { JSONObject jSONObject = new JSONObject(); Iterator iterator = ((Map)value).keySet().iterator(); while(iterator.hasNext()){ String key = iterator.next().toString(); Object valueObj = ((Map)value).get(key); jSONObject.put(key, getJSONObject(valueObj, useClassConvert)); } return new JSONStringObject(jSONObject.toString()); } //class if(value instanceof Class) return new JSONStringObject(JavascriptUtil.escapeJavaScript(((Class)value).getSimpleName())); //数组 if (value instanceof Collection || value.getClass().isArray()) { return new JSONStringObject(getJSONArray(proxyCheck(value), useClassConvert)); } return reflectObject(value, useClassConvert); }//value.equals(null) private JSONStringObject reflectObject(Object bean, boolean useClassConvert){ JSONObject jSONObject = new JSONObject(); Class klass = bean.getClass(); Method[] methods = klass.getMethods(); for (int i = 0; i < methods.length; i += 1) { try { Method method = methods[i]; String name = method.getName(); String key = ""; if (name.startsWith("get")) { key = name.substring(3); } else if (name.startsWith("is")) { key = name.substring(2); } if (key.length() > 0 && Character.isUpperCase(key.charAt(0)) && method.getParameterTypes().length == 0) { if (key.length() == 1) { key = key.toLowerCase(); } else if (!Character.isUpperCase(key.charAt(1))) { key = key.substring(0, 1).toLowerCase() + key.substring(1); } Object elementObj = method.invoke(bean, null); if(!useClassConvert && elementObj instanceof Class) continue; jSONObject.put(key, getJSONObject(elementObj, useClassConvert)); } } catch (Exception e) { /* forget about it */ } } return new JSONStringObject(jSONObject.toString()); }}
package com.aherp.framework.util;import org.json.JSONString;public class JSONStringObject implements JSONString { private String jsonString = null; public JSONStringObject(String jsonString){ this.jsonString = jsonString; } @Override public String toString() { return jsonString; } public String toJSONString() { return jsonString; }}
调用测试程序
import java.util.ArrayList;import java.util.HashMap;import java.util.List;public class AObj { private int ii = 7; private boolean bb = true; private String ss = "你好"; private List aList = new ArrayList(); public AObj(){ aList.add("hello"); aList.add(false); aList.add(new BObj()); aList.add(new HashMap()); } public boolean isBb() { return bb; } public void setBb(boolean bb) { this.bb = bb; } public int getIi() { return ii; } public void setIi(int ii) { this.ii = ii; } public String getSs() { return ss; } public void setSs(String ss) { this.ss = ss; } public List getAList() { return aList; } public void setAList(List list) { aList = list; }}import java.math.BigDecimal;import java.util.HashMap;public class BObj { private HashMap innerhm = new HashMap(); public BObj(){ double dd = 7.4354; innerhm.put("gigi", "高兴"); innerhm.put("sina", new BigDecimal(dd)); } public HashMap getInnerhm() { return innerhm; } public void setInnerhm(HashMap innerhm) { this.innerhm = innerhm; }}public class CObj extends AObj{ private Object[] oarray = new Object[]{352, false, "kick"}; public Object[] getOarray() { return oarray; } public void setOarray(Object[] oarray) { this.oarray = oarray; }}import org.json.JSONException;import com.aherp.framework.util.JSONUtil;public class Test { public static void main(String[] args) throws JSONException { CObj cObj = new CObj(); System.out.println(JSONUtil.toJSONString(cObj)); } } 输出：
{"AList":["hello",false,{"innerhm":{"gigi":"/u9AD8/u5174","sina":7.4353999999999995651478457148186862468719482421875}},{}],"ii":7,"oarray":[352,false,"kick"],"ss":"/u4F60/u597D","bb":true}
如 果需要支持Hibernate，那么必须弄清其机制。Hibernate采用CGLIB对VO对象进行字节码增加，实际机制就是使用一个原类型的 proxy子类，其子类实现了HibernateProxy接口。其接口有一个isUninitialized的判断方法，用来判断该代理类是否已经初始 化（还记得在事务外使用延迟加载的对象会抛no Session的错误吗，正是由于实际使用的对象已经变成原来类的子类proxy了）。而对于one-to-many映射时，很难判断对象只加载一次，因 此为了避免递归调用死循环，忽略了Hibernate的one-to-many集合的递归反射。其原理和many-to-one一样，也是一个子类化的 proxy，具有PersistentSet的接口。
因此，支持Hibernate的JSONUtil如下：
package com.aherp.framework.util;import org.hibernate.collection.PersistentSet;import org.hibernate.proxy.HibernateProxy;import org.hibernate.proxy.LazyInitializer;import org.json.JSONException;/** * 支持Hibernate的JSONUtil. * 自动检测是否已经代理加载，如果未加载，则将对象仅加载为OID * @author Jim Wu * */public class HiJSONUtil extends JSONUtil { private static HiJSONUtil instance = null; static public String toJSONString(Object obj) throws JSONException{ return toJSONString(obj, false); } static public String toJSONString(Object obj, boolean useClassConvert) throws JSONException{ if(instance == null) instance = new HiJSONUtil(); return instance.getJSONObject(obj, useClassConvert).toString(); } @Override protected Object proxyCheck(Object bean) { System.out.println("Class is ..." + bean.getClass().getName()); if(bean instanceof HibernateProxy){ LazyInitializer lazyInitializer = ((HibernateProxy)bean).getHibernateLazyInitializer(); if(lazyInitializer.isUninitialized()){ System.out.println(">>>>>lazyInitializer.getIdentifier()="+ lazyInitializer.getIdentifier()); return lazyInitializer.getIdentifier(); } } if(bean instanceof PersistentSet){ return new String[]{}; //忽略hibernate one-to-many } return bean; }};但是这样还是有个问题，当one-to-one具备双向映射关系时，会陷入调用递归死循环。因此避免这样的情况
