为实体类增加toJSON方法

public class BaseEntity implements Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = -5311594725961174392L;

    @Override
    public String toString() {
        try {
            return toJSON();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return null;
    }
    
    public String toJSON() throws IllegalArgumentException, IllegalAccessException {
        StringBuilder jsonBuff = new StringBuilder();
        jsonBuff.append("{");
        Field[] fields = this.getClass().getDeclaredFields();
        for (Field item : fields) {
            item.setAccessible(true);
            String name = item.getName();
            jsonBuff.append("\"" + name + "\"" + ":");
            Object value = item.get(this);
            if (value != null) {
                Class<?> type = item.getType();
                if (type.equals(String.class)) {
                    jsonBuff.append("\"" + value + "\"");
                } else if (type.equals(int.class) || type.equals(Integer.class)) {
                    jsonBuff.append(item.getInt(this));
                } else if (type.equals(short.class) || type.equals(Short.class)) {
                    jsonBuff.append(item.getShort(this));
                } else if (type.equals(long.class) || type.equals(Long.class)) {
                    jsonBuff.append(item.getLong(this));
                } else if (type.equals(float.class) || type.equals(Float.class)) {
                    jsonBuff.append(item.getFloat(this));
                } else if (type.equals(double.class) || type.equals(Double.class)) {
                    jsonBuff.append(item.getDouble(this));
                } else if (type.equals(char.class)) {
                    jsonBuff.append(item.getChar(this));
                } else if (type.equals(boolean.class)) {
                    jsonBuff.append(item.getBoolean(this));
                } else if (type.equals(Map.class)) {
                    jsonBuff.append(mapToString((Map)value));
                } else if (type.equals(List.class)) {
                    jsonBuff.append(listToString((List)value));
                } else if (type.getSuperclass().equals(BaseEntity.class)) {
                    jsonBuff.append(((BaseEntity)value).toJSON());
                }
            }
            jsonBuff.append(", ");
        }
        return jsonBuff.substring(0, jsonBuff.length() - 2) + "}";
    }
    
    public String mapToString(Map<String, ? extends Object> map) {
        StringBuilder buff = new StringBuilder();
        Iterator<String> iter = map.keySet().iterator();
        buff.append("{");
        while (iter.hasNext()) {
            String name = iter.next();
            Object value = map.get(name);
            buff.append("\"" + name + "\"" + ":");
            if (value != null) {
                String valueStr = String.valueOf(value);
                if (value.getClass().equals(String.class)) {
                    buff.append("\"" + valueStr + "\"");
                } else {
                    buff.append(valueStr);
                }
            }
            buff.append(", ");
        }
        return buff.substring(0, buff.length() - 2) + "}";
    }
    
    public String listToString(List<? extends Object> list) {
        StringBuilder buff = new StringBuilder();
        buff.append("[");
        for (Object value : list) {
            String valueStr = String.valueOf(value);
            if (value.getClass().equals(String.class)) {
                buff.append("\"" + valueStr + "\"");
            } else {
                buff.append(valueStr);
            }
            buff.append(", ");
        }
        return buff.substring(0, buff.length() - 2) + "]";
    }
}