這是一個將基本類、map集合、不是基本型別的欄位、list陣列、set陣列轉為json格式的util工具類

寫的不好，多多指教，希望大家有好的意見請提出。

public class JsonUtils {

    /**
     * @param obj
     * @return
     * @throws InstantiationException
     * @throws IllegalAccessException
     */
    public static String getJsonString(Object obj) throws InstantiationException, IllegalAccessException  {

        //如果傳入的物件為集合
        if (obj instanceof Collection) {

            //執行collectionTojson方法將集合型別轉為json格式
            return collectionTojson(obj);
 


        }

        //如果獲取的物件型別為一個Map集合
        else if (obj instanceof Map) {

            //執行mapTojson方法將Map型別轉為json格式
            return mapTojson(obj);

        }

        //如果獲取的物件型別為普通物件
        else{

            //執行classTojson方法將普通型別轉為json格式
            return classTojson(obj);

        }       
    }

    /**
     * @描述 將基本類轉為json格式
     * @param obj
     * @return
     * @throws IllegalArgumentException
     * @throws IllegalAccessException
     */
 

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

        //定義一個StringBuffer型別的字串
        StringBuffer buffer = new StringBuffer();
        buffer.append("[");

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

        //獲取類中所有的欄位
        Field[] declaredFields = clazz.getDeclaredFields
 
();

        //設定可以獲得私有欄位的value
        Field.setAccessible(declaredFields, true);                          

        //定義全域性變數
        boolean listf = false;
        boolean setf = false;
        Set<Object> set = null;
        List<Object> list = null;

        //遍歷獲取到的所有欄位
        for (Field field : declaredFields) {

            //getDeclaringClass()同getClasses()，但不侷限於public修飾，只要是目標類中宣告的內部類和介面均可

            String simpleName = clazz.getSimpleName();

             //判斷獲取到的型別
             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; 
             }

        }


        //如果獲取的物件型別為一個List集合
        if(listf == true){

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

        }

        //如果獲取的物件型別為一個Set集合
        if(setf == true){

            buffer = setTojson(set, buffer);

        }

        buffer.append("]");

        return buffer.toString();
    }


    /**
     * 描述 將基本類轉為json格式
     * @param obj
     * @return
     */
    private static String classTojson(Object obj){

        //通過反射獲取到類
        Class<? extends Object> clazz = obj.getClass();

        //獲取類中所有的欄位
        Field[] fields = clazz.getDeclaredFields();

        StringBuffer buffer = new StringBuffer();
        buffer.append("[{");

        //設定setAccessible方法能獲取到類中的私有屬性和方法
        Field.setAccessible(fields, true);

        //遍歷所有的方法和屬性
        for (Field field : fields) {

            try {

                Object object = field.get(obj);

                //獲取到該屬性對應型別名稱
                String fieldName = field.getType().getSimpleName();

                //如果該屬性的值為空
                if(object == null){

                    //根據型別判斷追加的值
                    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{

                    //獲取到該屬性的值對應的類
                    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"))
                {
                    //將獲取到的值強轉為list集合
                    List<Object> list = (List<Object>) object;
                    buffer.append("\""+field.getName()+"\":[");

                    //執行listTojson方法將獲取到的list轉為json格式
                    buffer = listTojson(buffer, list).append("]");
                }
                else if(simpleName.equals("HashSet")||simpleName.equals("TreeSet"))
                {
                    //將獲取到的值強轉為set集合
                    buffer.append("\""+field.getName()+"\":[");
                    Set<Object> set = (Set<Object>) object;

                    //執行setTojson方法將獲取到的set轉為json格式
                    buffer = setTojson(set, buffer).append("]");

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

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

                    //執行mapTojson方法將獲取到的map物件轉為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 將map集合轉為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;

        //通過Map.entrySet使用iterator(迭代器)遍歷key和value
        Set<Entry<Object, Object>> set = map.entrySet();  
        Iterator iterator = set.iterator();  
        buffer.append("{");

        while (iterator.hasNext()){  

            //使用Map.Entry接到通過迭代器迴圈出的set的值
            Map.Entry  mapentry = (Map.Entry) iterator.next();  
            Object value = mapentry.getValue();

            //使用getKey()獲取map的鍵，getValue()獲取鍵對應的值
            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 將不是基本型別的欄位轉為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 將list陣列轉為json格式
     * @param buffer
     * @param list
     * @return
     * @throws IllegalArgumentException
     * @throws IllegalAccessException
     */
    private static StringBuffer listTojson(StringBuffer buffer,List list) throws IllegalArgumentException, IllegalAccessException{

    //遍歷傳過來的list陣列
    for (Object object : list) {

        //判斷遍歷出的值是否為空
        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("{");
                //遍歷物件中的所有欄位獲取欄位值和欄位名稱拼成json字串
                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 將set陣列轉為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{

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

                //判斷集合中的值是否為java基本型別
                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("{");

                    //遍歷物件中的所有欄位獲取欄位值和欄位名稱拼成json字串
                    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;
    }

}