JSON Java端JavaBean/Collection与JSON对象的转换

JSON是AJAX编程中浏览器与WEB服务器之间一种轻型的基于文本的信息交换协议，其目的是作为XML信息格式的一种替代。它优于XML在于：
1. JSON在浏览器端是JAVASCRIPT对象的一种字面表达;
2.JSON是有类型的，而XML是无类型的。
JSON提供了JAVASCRIPT和JAVA工具方法和类型。但JAVA端类型太底层，只提供JSONObject和JSONArray等初级类型，没 有提供这些类型和JavaBean/Collection的直接转化。以下程序提供了这些类型之间的相互转换。对Map类型没有提供完整的转换，望读者根 据已存在的工具方法自己实现。

public static Object json2Bean(JSONObject json, Class beanClass, Map<String, Class> collectionComponentTypes) throws Exception: 完成JSONObject到JavaBean的转换，第三个参数说明的是JavaBean类型中有容器类型时，容器类型的属性名及其容器所含元素的类型。

public static JSONObject bean2Json(Object bean)：完成JavaBean到JSONObject的转换。

public static JSONArray collectionToJson(Object value)/public static JSONArray arrayToJarr(Object value) : 完成Collection/Array到JSONArray的转换。







package com.kettas.ajax.day3.json;

import java.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Collection;
import java.util.Date;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;

import org.json.JSONArray;
import org.json.JSONObject;

public class JsonUtil {
private static Class[] classes = {
byte.class, short.class, int.class,long.class,
float.class, double.class, boolean.class, char.class,
Byte.class, Short.class, Integer.class, Long.class,
Float.class, Double.class, Boolean.class, Character.class,
String.class
};

private static Class[] arrayClasses = {
byte[].class, short[].class, int[].class,long[].class,
float[].class, double[].class, boolean[].class, char[].class,
Byte[].class, Short[].class, Integer[].class, Long[].class,
Float[].class, Double[].class, Boolean[].class, Character[].class,
String[].class
};

public static Object json2Bean(JSONObject json, Class beanClass, Map<String, Class> collectionComponentTypes) throws Exception{
Object bean = null;
bean = beanClass.newInstance();

Method[] setters = getSetters(beanClass);
for(int i = 0; i < setters.length; i++){
Method setter = setters[i];
String property = getProperty(setter.getName());
if(property == null || json.get(property) == null) continue;
Class paramType = setter.getParameterTypes()[0];
if(isPrimitive(paramType)){
setter.invoke(bean, json.get(property));
} else if(isPrimitiveArray(paramType)){
JSONArray jarr = json.getJSONArray(property);
Object arr = Array.newInstance(getType(paramType), jarr.length());
for(int j = 0; j < jarr.length(); j++)
Array.set(arr, j, jarr.get(j));
setter.invoke(bean, arr);
}else if(paramType == java.util.Date.class){
setter.invoke(bean, new java.util.Date((long)json.getDouble(property)));
}else if(paramType == java.sql.Date.class){
setter.invoke(bean, new java.sql.Date((long)json.getDouble(property)));
}else if(paramType == java.sql.Time.class){
setter.invoke(bean, new java.sql.Time((long)json.getDouble(property)));
}else if(paramType == java.sql.Timestamp.class){
setter.invoke(bean, new java.sql.Timestamp((long)json.getDouble(property)));
}else if(paramType == java.util.Calendar.class){
java.util.Calendar c = java.util.Calendar.getInstance();
c.setTimeInMillis((long)json.getDouble(property));
setter.invoke(bean, c);
}else if(paramType == java.util.Set.class){
Class componentType = null;
if(collectionComponentTypes != null)
componentType = collectionComponentTypes.get(property);
java.util.Set s = new java.util.HashSet();
initCollection(s, json.getJSONArray(property), componentType, collectionComponentTypes);
setter.invoke(bean, s);
}else if(paramType == java.util.List.class ||
paramType == java.util.Collection.class){
Class componentType = null;
if(collectionComponentTypes != null)
componentType = collectionComponentTypes.get(property);
java.util.List l = new java.util.ArrayList();
initCollection(l, json.getJSONArray(property), componentType, collectionComponentTypes);
setter.invoke(bean, l);
}else if(paramType.getName().startsWith("[")){
Object[] arr = toObjectArray(paramType, json.getJSONArray(property), collectionComponentTypes);
setter.invoke(bean, arr);
}else{
setter.invoke(bean, json2Bean(json.getJSONObject(property), paramType, collectionComponentTypes));
}
}

return bean;
}

private static Class<?> getType(Class paramType) {
Class type = null;
for(int i = 0; i < arrayClasses.length; i++){
if(paramType == arrayClasses[i]){
type = classes[i];
}
}
return type;
}

public static Object[] toObjectArray(Class paramType, JSONArray jarr, Map<String, Class> collectionComponentTypes) throws Exception{
Object[] objs = new Object[jarr.length()];
Class beanClass = Class.forName(paramType.getName().substring(2));
for(int i = 0; i < objs.length; i++){
objs[i] = json2Bean(jarr.getJSONObject(i), beanClass, collectionComponentTypes);
}
return objs;
}

public static void initCollection(Collection c, JSONArray jarr, Class componentType, Map<String, Class> collectionComponentTypes) throws Exception{
//component of collection is primitive
if(componentType == null || isPrimitive(componentType)){
for(int i = 0; i < jarr.length(); i++ )
c.add(jarr.get(i));
}else if(componentType == java.util.Date.class){
for(int i = 0; i < jarr.length(); i++)
c.add(new java.util.Date((long)jarr.getDouble(i)));
}else if(componentType == java.sql.Date.class){
for(int i = 0; i < jarr.length(); i++)
c.add(new java.sql.Date((long)jarr.getDouble(i)));
}else if(componentType == java.sql.Time.class){
for(int i = 0; i < jarr.length(); i++)
c.add(new java.sql.Time((long)jarr.getDouble(i)));
}else if(componentType == java.sql.Timestamp.class){
for(int i = 0; i < jarr.length(); i++)
c.add(new java.sql.Timestamp((long)jarr.getDouble(i)));
}else if(componentType == java.util.Calendar.class){
for(int i = 0; i < jarr.length(); i++){
java.util.Calendar cal = java.util.Calendar.getInstance();
cal.setTimeInMillis((long)jarr.getDouble(i));
c.add(cal);
}
}else if(componentType != null){
for(int i = 0; i < jarr.length(); i++){
c.add(json2Bean(jarr.getJSONObject(i), componentType, collectionComponentTypes));
}
}
}

public static JSONObject bean2Json(Object bean){
Class clazz = bean.getClass();
JSONObject json = new JSONObject();
Method[] getters = getGetters(clazz);
int len = getters.length;
for(int i = 0; i < len; i++){
Method m = getters[i];
String property = getProperty(m.getName());
Class retType = m.getReturnType();
if(property == null || property.equals("class") )continue;
try {
Object value = m.invoke(bean, null);
if(isPrimitive(retType))
json.put(property, value);
else if(isPrimitiveArray(retType)){
JSONArray jarr = priArray(value);
json.put(property, jarr);
}else if(isDate(value)){
json.put(property, getTime(value));
}else if(value instanceof Collection){
json.put(property, collectionToJson(value));
}else if(retType.getName().startsWith("[")){
json.put(property, arrayToJarr(value));
}else if(value instanceof Map){
json.put(property, new JSONObject((Map)value));
}
else{
json.put(property, bean2Json(value));
}
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException("Error to get value");
}
}

return json;
}

public static JSONArray arrayToJarr(Object value) {
// TODO Auto-generated method stub
Object[] arr = (Object[])value;
Collection c = new ArrayList();
for(Object o : arr)
c.add(o);
return collectionToJson(c);
}

public static JSONArray collectionToJson(Object value) {
// TODO Auto-generated method stub
JSONArray jarr = new JSONArray();
Collection c = (Collection)value;
for(Object o : c){
Class type = o.getClass();
if(isPrimitive(type)) jarr.put(o);
else if(isPrimitiveArray(type)) jarr.put(priArray(o));
else if(isDate(o)) jarr.put(getTime(o));
else if(o instanceof Collection) jarr.put(collectionToJson(o));
else if(type.getName().startsWith("[")) jarr.put(arrayToJarr(o));
else if(o instanceof Map) jarr.put(new JSONObject((Map)o));
else jarr.put(bean2Json(o));
}

return jarr;
}

private static Object getTime(Object value) {
// TODO Auto-generated method stub
if(value instanceof Date)
return ((Date)value).getTime() ;
return ((Calendar)value).getTimeInMillis();
}

private static boolean isDate(Object value){
return value instanceof Date ||
value instanceof Calendar;
}

public static JSONArray priArray(Object value){
JSONArray jarr = new JSONArray();
int arLen = Array.getLength(value);
for(int j = 0; j < arLen; j++){
jarr.put(Array.get(value, j));
}

return jarr;
}

private static String getProperty(String name) {
// TODO Auto-generated method stub
if(name.startsWith("get") || name.startsWith("set")) name = name.substring(3);
else name = name.substring(2);
if(name.length() > 0){
StringBuilder sb = new StringBuilder(name.length());
char first = name.charAt(0);
if(name.length() > 1){
char second = name.charAt(1);
if(second >='A' && second <='Z');
else first += 32;
}
sb.append(first).append(name.substring(1));
return sb.toString();
}

return null;
}

private static Method[] getGetters(Class clazz){
Method[] methods = clazz.getMethods();
ArrayList<Method> getters = new ArrayList<Method>();
for(int i = 0; i < methods.length; i++){
if(methods[i].getName().startsWith("get") ||
methods[i].getName().startsWith("is") ){
Class[] paramTypes = methods[i].getParameterTypes();
if(paramTypes == null || paramTypes.length == 0 )
getters.add(methods[i]);
}
}

Method[] retMethods = new Method[getters.size()];
int i = 0;
for(Method m : getters){
retMethods[i++] = m;
}

return retMethods;
}

private static Method[] getSetters(Class clazz){
Method[] methods = clazz.getMethods();
ArrayList<Method> setters = new ArrayList<Method>();
for(int i = 0; i < methods.length; i++){
if(methods[i].getName().startsWith("set")){
if(methods[i].getParameterTypes() != null &&
methods[i].getParameterTypes().length == 1) setters.add(methods[i]);
}
}

Method[] retMethods = new Method[setters.size()];
int i = 0;
for(Method m : setters){
retMethods[i++] = m;
}

return retMethods;
}

private static boolean isPrimitive(Class clazz){
for(int i = 0; i < classes.length; i++){
if(classes[i] == clazz) return true;
}

return false;
}

private static boolean isPrimitiveArray(Class clazz){
for(int i = 0; i < arrayClasses.length; i++){
if(arrayClasses[i] == clazz) return true;
}

return false;
}

private static boolean isSpecificClass(Class clazz){
return isPrimitive(clazz) || isPrimitiveArray(clazz);
}
}