自己实现Java中List对象转换为JSON对象

Posted 2020-10-08

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();  
  }  
}