List对象转化为JSON数据

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;

public class FromObjectToJson<T> {
    public  String ToJson(List<T> list) {
        // 变量
        StringBuffer jsonStr = new StringBuffer();
        // 前提条件
        if (null == list || 0 == list.size()) {
            return null;
        }
        // class对象
        Class<?> classType = list.get(0).getClass();
        // 得到javabean的名字
        String javaBeanClassName = classType.getSimpleName();

        jsonStr.append("{\"").append(javaBeanClassName.toLowerCase()).append("s").append("\":[");
        // 此JavaBean中所声明的所有字段
        Field[] fields = classType.getDeclaredFields();
        for (int i = 0; i < list.size(); i++) {
            jsonStr.append("{");
            for (Field field : fields) {
                // 得到字段名
                String fieldName = field.getName();
                field.setAccessible(true);
                // 得到指定对象上此 Field 表示的字段的值
                Object fieldValue;
                try {
                    fieldValue = field.get(list.get(i));
                    jsonStr.append("\"").append(fieldName.toLowerCase()).append("\":").append("\"").append(fieldValue)
                            .append("\"").append(",");
                } catch (IllegalArgumentException e) {
                    e.printStackTrace();
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            }
            jsonStr.deleteCharAt(jsonStr.length() - 1);
            jsonStr.append("},");
        }
        jsonStr.deleteCharAt(jsonStr.length() - 1);
        jsonStr.append("]}");
        return jsonStr.toString();
    }


    public static void main(String[] args) {
        List<UserModel> list = new ArrayList<UserModel>();
        UserModel  userModel1 = new UserModel(1, "张三", "男");
        UserModel  userModel2 = new UserModel(2, "李四", "男");
        UserModel  userModel3 = new UserModel(3, "美女", "女");
        list.add(userModel1);
        list.add(userModel2);
        list.add(userModel3);
        String json_string = new FromObjectToJson<UserModel>().ToJson(list);
        System.out.println("\n json数据:" + json_string);

    }
}           

1.效果图如下显示

json数据:{"usermodels":[{"id":"1","name":"张三","sex":"男"},{"id":"2","name":"李四","sex":"男"},{"id":"3","name":"美女","sex":"女"}]}