JAVA  封装一个工具类，将实例的里面的空值设为对应的默认值，比喻字符串类型就设为默认 "", Integer就设为0  

示例代码：

    protected static void setDefaults(Object obj) {
        Class<?> clazz = obj.getClass();
        Field[] fields = clazz.getDeclaredFields();

        for (Field field : fields) {
            field.setAccessible(true); // 允许访问私有字段
            try {
                Object fieldValue = field.get(obj);
                if (fieldValue == null) {
                    System.out.println(field.getType()+"-"+field.getType().isPrimitive());
                    if (field.getType().isPrimitive() || field.getType() == String.class) {
                        // 对于基本类型和String，直接设置默认值
                        setDefaultValue(field, obj);

                    } else if (field.getType() == Integer.class || field.getType() == Integer.TYPE) {
                        // 对于Integer类型，设置默认值0
                        field.set(obj, 0);
                    } else if (field.getType() == Double.class || field.getType() == Double.TYPE) {
                        field.set(obj, 0.0);
                    } else if (field.getType() == Long.class || field.getType() == Long.TYPE) {
                        field.set(obj, 0L);
                    } else {
                        // 对于其他类型，不做处理
                        continue;
                    }
                }
            } catch (IllegalAccessException e) {
                throw new RuntimeException("Failed to access field: " + field.getName(), e);
            }
        }
    }

    private void setDefaultValue(Field field, Object obj) throws IllegalAccessException {
        if (field.getType() == boolean.class || field.getType() == Boolean.class) {
            field.setBoolean(obj, false);
        } else if (field.getType() == byte.class || field.getType() == Byte.class) {
            field.setByte(obj, (byte) 0);
        } else if (field.getType() == char.class || field.getType() == Character.class) {
            field.setChar(obj, '\u0000');
        } else if (field.getType() == short.class || field.getType() == Short.class) {
            field.setShort(obj, (short) 0);
        } else if (field.getType() == int.class || field.getType() == Integer.class) {
            field.setInt(obj, 0);
        } else if (field.getType() == long.class || field.getType() == Long.class) {
            field.setLong(obj, 0L);
        } else if (field.getType() == float.class || field.getType() == Float.class) {
            field.setFloat(obj, 0.0f);
        } else if (field.getType() == double.class || field.getType() == Double.class){
            field.setDouble(obj, 0.0);
        }

    }

使用：

    public static void main(String[] args) {
        CZKInfoDTO dto=new CZKInfoDTO();
        setDefaults(dto);
        System.out.println(JSON.toJSONString(dto));
    }

运行结果：

而使用设置得到的结果：