自己实现Java中List对象转换为JSON对象

1.在你的MyEclipse里新建一个Web Project,就叫Ajax_Json吧。

2.新建一个类，名字叫做JsonUtil.java，打包到young.ajax.json，把下面代码复制进去。

package young.ajax.json;  

import java.beans.IntrospectionException;  

import java.beans.Introspector;  

import java.beans.PropertyDescriptor;  

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
public class JsonUtil {
private static Log log = LogFactory.getLog(JsonUtil.class);
public static String object2json(Object obj) {
             StringBuilder json = new StringBuilder();
             if (obj == null) {
               json.append("\"\"");
             } else if (obj instanceof String || obj instanceof Integer || obj instanceof Float
                 || obj instanceof Boolean || obj instanceof Short || obj instanceof Double
                 || obj instanceof Long || obj instanceof BigDecimal || obj instanceof BigInteger
                 || obj instanceof Byte) {
               json.append("\"").append(string2json(obj.toString())).append("\"");
             } else if (obj instanceof Object[]) {
               json.append(array2json((Object[]) obj));
             } else if (obj instanceof List) {
               json.append(list2json((List<?>) obj));
             } else if (obj instanceof Map) {
               json.append(map2json((Map<?, ?>) obj));
             } else if (obj instanceof Set) {
               json.append(set2json((Set<?>) obj));
             } else {
               json.append(bean2json(obj));
             }
             return json.toString();
  }
public static String bean2json(Object bean) {
             StringBuilder json = new StringBuilder();
             json.append("{");
             PropertyDescriptor[] props = null;
             try {
               props = Introspector.getBeanInfo(bean.getClass(), Object.class).getPropertyDescriptors();
             } catch (IntrospectionException e) {}
             if (props != null) {
               for (int i = 0; i < props.length; i++) {
                 try {
                   String name = object2json(props[i].getName());
                   String value = object2json(props[i].getReadMethod().invoke(bean));
                   json.append(name);
                   json.append(":");
                   json.append(value);
                   json.append(",");
                 } catch (Exception e) {}
               }
               json.setCharAt(json.length() - 1, ‘}‘);
             } else {
               json.append("}");
             }
             return json.toString();
  }
public static String list2json(List<?> list) {
             StringBuilder json = new StringBuilder();
             json.append("[");
             if (list != null && list.size() > 0) {
               for (Object obj : list) {
                 json.append(object2json(obj));
                 json.append(",");
               }
               json.setCharAt(json.length() - 1, ‘]‘);
             } else {
               json.append("]");
             }
             return json.toString();
  }
public static String array2json(Object[] array) {
             StringBuilder json = new StringBuilder();
             json.append("[");
             if (array != null && array.length > 0) {
               for (Object obj : array) {
                 json.append(object2json(obj));
                 json.append(",");
               }
               json.setCharAt(json.length() - 1, ‘]‘);
             } else {
               json.append("]");
             }
             return json.toString();
  }
public static String map2json(Map<?, ?> map) {
             StringBuilder json = new StringBuilder();
             json.append("{");
             if (map != null && map.size() > 0) {
               for (Object key : map.keySet()) {
                 json.append(object2json(key));
                 json.append(":");
                 json.append(object2json(map.get(key)));
                 json.append(",");
               }
               json.setCharAt(json.length() - 1, ‘}‘);
             } else {
               json.append("}");
             }
             return json.toString();
  }
public static String set2json(Set<?> set) {
             StringBuilder json = new StringBuilder();
             json.append("[");
             if (set != null && set.size() > 0) {
               for (Object obj : set) {
                 json.append(object2json(obj));
                 json.append(",");
               }
               json.setCharAt(json.length() - 1, ‘]‘);
             } else {
               json.append("]");
             }
             return json.toString();
  }
public static String string2json(String s) {
             if (s == null)
               return "";
             StringBuilder sb = new StringBuilder();
             for (int i = 0; i < s.length(); i++) {
               char ch = s.charAt(i);
               switch (ch) {
               case ‘"‘:
                 sb.append("\\\"");
                 break;
               case ‘\\‘:
                 sb.append("\\\\");
                 break;
               case ‘\b‘:
                 sb.append("\\b");
                 break;
               case ‘\f‘:
                 sb.append("\\f");
                 break;
               case ‘\n‘:
                 sb.append("\\n");
                 break;
               case ‘\r‘:
                 sb.append("\\r");
                 break;
               case ‘\t‘:
                 sb.append("\\t");
                 break;
               case ‘/‘:
                 sb.append("\\/");
                 break;
               default:
                 if (ch >= ‘\u0000‘ && ch <= ‘\u001F‘) {
                   String ss = Integer.toHexString(ch);
                   sb.append("\\u");
                   for (int k = 0; k < 4 - ss.length(); k++) {
                     sb.append(‘0‘);
                   }
                   sb.append(ss.toUpperCase());
                 } else {
                   sb.append(ch);
                 }
               }
             }
             return sb.toString();
  }
}