java反射实现对象转JSON(粘贴可用)


package test;

import java.text.SimpleDateFormat;

import java.util.Collection;

import java.util.Date;

import java.util.Iterator;

import java.util.List;

import java.util.Map.Entry;

import java.util.Set;

import java.lang.reflect.Field;

import java.util.Map;

public class JsonUtils {

 

 /**

  * @param obj

  * @return

  * @throws InstantiationException

  * @throws IllegalAccessException

  */

 public static String getJsonString(Object obj) throws InstantiationException, IllegalAccessException  {

  

  //如果传入的对象为集合

  if (obj instanceof Collection) {

   

   //执行collectionTojson方法将集合类型转为json格式

   return collectionTojson(obj);

   

  }

  

  //如果获取的对象类型为一个Map集合

  else if (obj instanceof Map) {

   

   //执行mapTojson方法将Map类型转为json格式

   return mapTojson(obj);

  

  }

  

  //如果获取的对象类型为普通对象

  else{

   

   //执行classTojson方法将普通类型转为json格式

   return classTojson(obj);

   

  }  

 }

   

 /**

  * @描述 将集合转为json格式的字符串

  * @param obj

  * @return

  * @throws IllegalArgumentException

  * @throws IllegalAccessException

  */

 private static String collectionTojson(Object obj) throws IllegalArgumentException, IllegalAccessException{

  

  //定义一个StringBuffer类型的字符串

  StringBuffer buffer = new StringBuffer();

  buffer.append("[");

  

  Class<? extends Object> clazz = obj.getClass();

  

  //获取类中所有的字段

  Field[] declaredFields = clazz.getDeclaredFields();

  

  //设置可以获得私有字段的value

  Field.setAccessible(declaredFields, true);       

  

  //定义全局变量

  boolean listf = false;

  boolean setf = false;

  Set<Object> set = null;

  List<Object> list = null;

  

  //遍历获取到的所有字段

  for (Field field : declaredFields) {

   

   //getDeclaringClass()同getClasses()，但不局限于public修饰，只要是目标类中声明的内部类和接口均可

   

   String simpleName = clazz.getSimpleName();

   

    //判断获取到的类型

    if(simpleName.equals("ArrayList")||simpleName.equals("LinkedList")){

    list = (List<Object>) obj;

    listf=true;

    }

    if(simpleName.equals("HashSet")||simpleName.equals("TreeSet")){

     set = (Set<Object>) obj;

     setf=true;

    }

   

  }

  

  

  //如果获取的对象类型为一个List集合

  if(listf == true){

   

   return listTojson(buffer, list).toString();

  

  }

  

  //如果获取的对象类型为一个Set集合

  if(setf == true){

   

   buffer = setTojson(set, buffer);

  

  }

  

  buffer.append("]");

  

  return buffer.toString();

 }

 

 

 /**

  * 描述 将基本类转为json格式

  * @param obj

  * @return

  */

 private static String classTojson(Object obj){

  

  //通过反射获取到类

  Class<? extends Object> clazz = obj.getClass();

  

  //获取类中所有的字段

  Field[] fields = clazz.getDeclaredFields();

  

  StringBuffer buffer = new StringBuffer();

  buffer.append("[{");

  

  //设置setAccessible方法能获取到类中的私有属性和方法

  Field.setAccessible(fields, true);

  

  //遍历所有的方法和属性

  for (Field field : fields) {

   

   try {

    

    Object object = field.get(obj);

    

    //获取到该属性对应类型名称

    String fieldName = field.getType().getSimpleName();

    

    //如果该属性的值为空

    if(object == null){

     

     //根据类型判断追加的值

     if(fieldName.equals("String"))

     {

      buffer.append("\""+field.getName()+"\":\"\",");

     }

     else if(fieldName.equals("Boolean")||fieldName.equals("Integer")||fieldName.equals("Double")||fieldName.equals("Float")||fieldName.equals("Long")){

      

      buffer.append("\""+field.getName()+"\":0,");

     }

    

     else{

      buffer.append("\""+field.getName()+"\":null,");

     }

     

    }

    else{

     

     //获取到该属性的值对应的类

     Class<? extends Object> fieldclass = object.getClass();

     String simpleName = fieldclass.getSimpleName();

    

    if(simpleName.equals("String")){

     

     buffer.append("\""+field.getName()+"\":\""+field.get(obj)+"\",");

    

    }

    else if(simpleName.equals("Boolean")||simpleName.equals("Integer")||simpleName.equals("Double")||simpleName.equals("Float")||simpleName.equals("Long")){

     

     buffer.append("\""+field.getName()+"\":"+field.get(obj)+",");

    

    }

    else if(simpleName.equals("Date")){

     

     Date date = (Date) object;

     SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

     String simdate = simpleDateFormat.format(date);

     buffer.append("\""+field.getName()+"\":\""+simdate+"\",");

    

    }

    else if(simpleName.equals("ArrayList")||simpleName.equals("LinkedList"))

    {

     //将获取到的值强转为list集合

     List<Object> list = (List<Object>) object;

     buffer.append("\""+field.getName()+"\":[");
     

     //执行listTojson方法将获取到的list转为json格式

     buffer = listTojson(buffer, list).append("]");

    }

    else if(simpleName.equals("HashSet")||simpleName.equals("TreeSet"))

    {

     //将获取到的值强转为set集合

     buffer.append("\""+field.getName()+"\":[");

     Set<Object> set = (Set<Object>) object;

     

     //执行setTojson方法将获取到的set转为json格式

     buffer = setTojson(set, buffer).append("]");

    

    }

    else if(simpleName.equals("HashMap")||simpleName.equals("HashTable"))

    {

     buffer.append("\""+field.getName()+"\":");

     

     //执行mapTojson方法将获取到的map对象转为json格式

     StringBuffer mapbuffer = new StringBuffer(mapTojson(object));

     mapbuffer.deleteCharAt(0);

     buffer.append(mapbuffer);

    }

    else{

      

      buffer = beanTojson(object,buffer).append(",");

     }

    }

    

   } catch (Exception e) {

    // TODO Auto-generated catch block

    e.printStackTrace();

   }

  

  }

  buffer = new StringBuffer(buffer.substring(0,buffer.length()-1));

  buffer.append("}]");

  

  return buffer.toString();

 }

 /**

  * 描述 将map集合转为json格式

  * @param obj

  * @return

  * @throws IllegalArgumentException

  * @throws IllegalAccessException

  */

 private static String mapTojson(Object obj) throws IllegalArgumentException, IllegalAccessException{

  

  StringBuffer buffer = new StringBuffer();

  Class<? extends Object> clazz = obj.getClass();

  Field[] declaredFields = clazz.getDeclaredFields();

  Field.setAccessible(declaredFields, true);

  buffer.append("[");

  Map<Object,Object> map = (Map<Object, Object>) obj;

  

  //通过Map.entrySet使用iterator(迭代器)遍历key和value

  Set<Entry<Object, Object>> set = map.entrySet(); 

        Iterator iterator = set.iterator(); 

        buffer.append("{");

       

        while (iterator.hasNext()){ 

         

         //使用Map.Entry接到通过迭代器循环出的set的值

            Map.Entry  mapentry = (Map.Entry) iterator.next(); 

            Object value = mapentry.getValue();

           

            //使用getKey()获取map的键，getValue()获取键对应的值

            String valuename = value.getClass().getSimpleName();

            if(valuename.equals("String")){

    

    buffer.append("\""+mapentry.getKey()+"\":\""+mapentry.getValue()+"\",");

   }

   else if(valuename.equals("Boolean")||valuename.equals("Integer")||valuename.equals("Double")||valuename.equals("Float")||valuename.equals("Long")){

    

    buffer.append("\""+mapentry.getKey()+"\":"+mapentry.getValue()+",");

   }

   else if(valuename.equals("Date")){

    Date date = (Date) value;

    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

    String simdate = simpleDateFormat.format(date);

    buffer.append("\""+mapentry.getKey()+"\":\""+simdate+"\",");

   }else if(valuename.equals("ArrayList")||valuename.equals("LinkedList"))

   {

    List<Object> list = (List<Object>) value;

    buffer.append("\""+mapentry.getKey()+"\":[");

    buffer = listTojson(buffer, list).append("]");

   }

   else if(valuename.equals("HashSet")||valuename.equals("TreeSet"))

   {

    buffer.append("\""+mapentry.getKey()+"\":[");

    Set<Object> sets = (Set<Object>) value;

    buffer = setTojson(sets, buffer).append("]");

   }

   else if(valuename.equals("HashMap")||valuename.equals("HashTable"))

   {

    buffer.append("\""+mapentry.getKey()+"\":");

    StringBuffer mapbuffer = new StringBuffer(mapTojson(value));

    mapbuffer.deleteCharAt(0);

    buffer.append(mapbuffer);

   }

            else{

             buffer.append("\""+mapentry.getKey()+"\":");

             buffer.append("{");

             

             Class<? extends Object> class1 = value.getClass();

             Field[] fields = class1.getDeclaredFields();

             Field.setAccessible(fields, true);

             

             for (Field field : fields) {

              

              Object object = field.get(value);

              String fieldName = field.getType().getSimpleName();

              

     if(object == null){

      if(fieldName.equals("String"))

      {

       buffer.append("\""+field.getName()+"\":\"\",");

      }

     

      else{

       buffer.append("\""+field.getName()+"\":null,");

      }

      

     }

              else{

               

               Class<? extends Object> fieldclass = field.get(value).getClass();

               String simpleName = fieldclass.getSimpleName();

               if(simpleName.equals("String")){

       

       buffer.append("\""+field.getName()+"\":\""+field.get(value)+"\",");

      }

      else if(simpleName.equals("Boolean")||simpleName.equals("Integer")||simpleName.equals("Double")||simpleName.equals("Float")||simpleName.equals("Long")){

       

       buffer.append("\""+field.getName()+"\":"+field.get(value)+",");

      }

      else if(simpleName.equals("Date")){

       Date date = (Date) object;

       SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

       String simdate = simpleDateFormat.format(date);

       buffer.append("\""+field.getName()+"\":\""+simdate+"\",");

      }

      else if(simpleName.equals("ArrayList")||simpleName.equals("LinkedList")){

       

       List<Object> list = (List<Object>) object;

       buffer.append("\""+field.getName()+"\":[");

       StringBuffer append = listTojson(buffer, list).append("]");

       buffer.append(append);

      }

      else if(simpleName.equals("HashSet")||simpleName.equals("TreeSet")){

       

       buffer.append("\""+field.getName()+"\":[");

       Set<Object> sets = (Set<Object>) object;

       buffer = setTojson(sets, buffer).append("]");

      }

      else if(simpleName.equals("HashMap")||simpleName.equals("HashTable")){

       

       buffer.append("\""+field.getName()+"\":");

       StringBuffer mapbuffer = new StringBuffer(mapTojson(object));

       mapbuffer.deleteCharAt(0);

       buffer.append(mapbuffer);

      }

      else{

       buffer = beanTojson(object,buffer).append(",");

        

      }

              }

     

    }

             

             buffer =  new StringBuffer(""+buffer.substring(0,buffer.length()-1)+"");

             buffer.append("},");

            }

             

          }

       

         buffer =  new StringBuffer(""+buffer.substring(0,buffer.length()-1)+"");

   return buffer.toString()+"}]";

 }

 /**

  * @描述 将不是基本类型的字段转为json格式

  * @param obj

  * @param buffer

  * @return

  * @throws IllegalArgumentException

  * @throws IllegalAccessException

  */

 private static StringBuffer beanTojson(Object obj,StringBuffer buffer) throws IllegalArgumentException, IllegalAccessException{

  

  Class<? extends Object> clazz = obj.getClass();

  Field[] declaredFields = clazz.getDeclaredFields();

  Field.setAccessible(declaredFields, true);

  

  buffer.append("\""+clazz.getSimpleName()+"\":{");

  

  for (Field field : declaredFields) {

   

   Object object = field.get(obj);

   String fieldName = field.getType().getSimpleName();

   

   if(object == null){

    if(fieldName.equals("String"))

    {

     buffer.append("\""+field.getName()+"\":\"\",");

    }

   

    else{

     buffer.append("\""+field.getName()+"\":null,");

    }

    

   }

   else{

    

   Class<? extends Object> fieldclass = object.getClass();

   String simpleName = fieldclass.getSimpleName();

   

   if(simpleName.equals("String")){

    

    buffer.append("\""+field.getName()+"\":\""+field.get(obj)+"\",");

   }

   else if(simpleName.equals("Boolean")||simpleName.equals("Integer")||simpleName.equals("Double")||simpleName.equals("Float")||simpleName.equals("Long")){

    

    buffer.append("\""+field.getName()+"\":"+field.get(obj)+",");

   }

   else if(simpleName.equals("Date")){

    

    Date date = (Date) object;

    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

    String simdate = simpleDateFormat.format(date);

    buffer.append("\""+field.getName()+"\":\""+simdate+"\",");

   }

   else if(simpleName.equals("ArrayList")||simpleName.equals("LinkedList")){

    

    List<Object> list = (List<Object>) object;

    buffer = listTojson(buffer, list);

   }

   else if(simpleName.equals("HashSet")||simpleName.equals("TreeSet")){

    

    Set<Object> set = (Set<Object>) object;

    buffer = setTojson(set, buffer);

   }

   else if(simpleName.equals("HashMap")||simpleName.equals("HashTable")){

    

    buffer.append("\""+field.getName()+"\":");

    StringBuffer mapbuffer = new StringBuffer(mapTojson(object));

    mapbuffer.deleteCharAt(0);

    buffer.append(mapbuffer);

   }

   else{

     buffer = beanTojson(object,buffer).append("}");

    }

   }

   

  }

  

  buffer =  new StringBuffer(""+buffer.substring(0,buffer.length()-1)+"");

  buffer.append("}");

  

  return buffer;

 }

 

 /**

  * @描述 将list数组转为json格式

  * @param buffer

  * @param list

  * @return

  * @throws IllegalArgumentException

  * @throws IllegalAccessException

  */

 private static StringBuffer listTojson(StringBuffer buffer,List list) throws IllegalArgumentException, IllegalAccessException{

  

 //遍历传过来的list数组

 for (Object object : list) {

   

  //判断遍历出的值是否为空

  if (object == null) {

   buffer.append(","); 

  }

  else{

    

   Class<? extends Object> class1 = object.getClass();

   String simpleName = class1.getSimpleName();

    

   if(simpleName.equals("String")){

     

    buffer.append("\""+object.toString()+"\",");

   }

   else if(simpleName.equals("Boolean")||simpleName.equals("Integer")||simpleName.equals("Double")||simpleName.equals("Float")||simpleName.equals("Long")){

     

    buffer.append(""+object.toString()+",");

   }

   else if(simpleName.equals("Date")){

    Date date = (Date) object;

    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

    String simdate = simpleDateFormat.format(date);

    buffer.append(""+simdate+",");

   }

   else{

     

    Class<? extends Object> class2 = object.getClass();

    Field[] fields = class2.getDeclaredFields();

    Field.setAccessible(fields, true);

    buffer.append("{");

    //遍历对象中的所有字段获取字段值和字段名称拼成json字符串

    for (Field field : fields) {

      

     Object fieldobj = field.get(object);

     String fieldName = field.getType().getSimpleName();

      

     if(fieldobj == null){

       

      if(fieldName.equals("String"))

      {

       buffer.append("\""+field.getName()+"\":\"\",");

      }

      

      else{

       buffer.append("\""+field.getName()+"\":null,");

      }

       

     }

      

     else{

       

      String fsimpleName = fieldobj.getClass().getSimpleName();

       

      if(fsimpleName.equals("String")){

        

       buffer.append("\""+field.getName()+"\":\""+field.get(object)+"\",");

      }

      else if(fsimpleName.equals("Boolean")||fsimpleName.equals("Integer")||fsimpleName.equals("Double")||fsimpleName.equals("Float")||fsimpleName.equals("Long")){

        

       buffer.append("\""+field.getName()+"\":"+field.get(object)+",");

      }

      else if(fsimpleName.equals("Date")){

       

       Date date = (Date) object;

       SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

       String simdate = simpleDateFormat.format(date);

       buffer.append("\""+field.getName()+"\":"+simdate+",");

      }

      else{

       

       buffer = beanTojson(fieldobj, buffer).append(",");

      }

     }

      

    }

     

    buffer =  new StringBuffer(""+buffer.substring(0,buffer.length()-1)+"");

    buffer.append("},");

   }

   }

   

  }

  

  buffer =  new StringBuffer(""+buffer.substring(0,buffer.length()-1)+"");

  buffer.append("]");

  

  return buffer;

 }

 

 

 

 /**

  * @描述 将set数组转为json格式

  * @param set

  * @param buffer

  * @return

  * @throws IllegalArgumentException

  * @throws IllegalAccessException

  */

 private static StringBuffer setTojson(Set set,StringBuffer buffer) throws IllegalArgumentException, IllegalAccessException{

  

  for (Object object : set) {

   if (object == null) {

    buffer.append(""+"null"+","); 

   }

   else{

    

  
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  Class<? extends Object> class1 = object.getClass();

    

    //判断集合中的值是否为java基本类型

    String simpleName = class1.getSimpleName();

    if(simpleName.equals("String")){

     

     buffer.append("\""+object.toString()+"\",");

    }

    else if(simpleName.equals("Boolean")||simpleName.equals("Integer")||simpleName.equals("Double")||simpleName.equals("Float")||simpleName.equals("Long")){

     

     buffer.append(""+object.toString()+",");

    }

    else if(simpleName.equals("Date")){

     

     Date date = (Date) object;

     SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

     String simdate = simpleDateFormat.format(date);

     buffer.append(""+simdate+",");

    }

    else{

     

     Class<? extends Object> class2 = object.getClass();

     Field[] fields = class2.getDeclaredFields();

     Field.setAccessible(fields, true);

     buffer.append("{");

     

     //遍历对象中的所有字段获取字段值和字段名称拼成json字符串

     for (Field field : fields) {

      

      Object fieldobj = field.get(object);

      String fieldName = field.getType().getSimpleName();

      

      if(object == null){

       if(fieldName.equals("String"))

       {

        buffer.append("\""+field.getName()+"\":\"\",");

       }

      

       else{

        buffer.append("\""+field.getName()+"\":null,");

       }

       

      }

      else{

       

       String fsimpleName = fieldobj.getClass().getSimpleName();

       if(fsimpleName.equals("String")){

        

        buffer.append("\""+field.getName()+"\":\""+field.get(object)+"\",");

       }

       else if(fsimpleName.equals("Boolean")||fsimpleName.equals("Integer")||fsimpleName.equals("Double")||fsimpleName.equals("Float")||fsimpleName.equals("Long")){

        

        buffer.append("\""+field.getName()+"\":"+field.get(object)+",");

       }

       else if(fsimpleName.equals("Date")){

        

        Date date = (Date) object;

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

        String simdate = simpleDateFormat.format(date);

        buffer.append("\""+field.getName()+"\":"+simdate+",");

       }

       else{

        

        buffer = beanTojson(fieldobj, buffer).append(",");

       }

      } 

     }

     

     buffer =  new StringBuffer(""+buffer.substring(0,buffer.length()-1)+"");

     buffer.append("},");

    }

   }

  }

  

  buffer =  new StringBuffer(""+buffer.substring(0,buffer.length()-1)+"");

  return buffer;

 }

      

}