注解+反射参数校验更加简洁

本文主要是介绍注解+反射参数校验更加简洁，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

背景

做RPC接口的时候我们需要对一些字段做非空校验在字段很多的情况下如果一个一个的用if判断代码会很恶心所以我们需要有一种便捷的方式去实现这个功能比如使用注解+反射的方式

怎么做？

首先定义注解
非空注解：

package com.api.annotation;import java.lang.annotation.*;/*** 非空校验注解*/@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface NotNull {String message() default "";
}

数值注解：

package com.api.annotation;import java.lang.annotation.*;/*** 数字类型校验注解*/@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Number {String message() default "";
}

日期注解：

package com.api.annotation;import java.lang.annotation.*;/*** 日期格式校验注解*/@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Date {String message() default "";String format() default "yyyy-MM-dd HH:mm:ss";
}

接下来定义一下校验的返回值

public class BaseResultInfo {/*** 响应码*/protected int code = 200;/*** 响应消息*/protected String msg = "OK";public int getCode() {return code;}public void setCode(int code) {this.code = code;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}

再定义一个返回码的枚举：

public enum ResultCodeEnum {SUCCESS(200,"成功"),PARAM_ERROR(1,"参数异常！！"),SYSTEM_ERROR(2,"系统异常！");ResultCodeEnum(int code, String msg) {this.code = code;this.msg = msg;}/*** 返回code*/private int code;/*** 错误消息*/private String msg;public int getCode() {return code;}public void setCode(int code) {this.code = code;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}
}

接下来定义一个基类包含一个校验方法通过反射来对字段进行校验

@Service
public class BaseService {/*** 验证某个bean的参数** @param object 被校验的参数*//*** 验证某个bean的参数* @param object        校验bean对象* @param resultInfo    校验结果* @param <T>* @return* @throws Exception*/public <T> BaseResultInfo validate(T object, BaseResultInfo resultInfo) throws Exception {if(object == null){resultInfo.setCode(ResultCodeEnum.PARAM_ERROR.getCode());resultInfo.setMsg("入参对象不能为null");return resultInfo;}//获取object的类型Class<? extends Object> clazz = object.getClass();//获取该类型声明的成员Field[] fields = clazz.getDeclaredFields();//遍历属性for (Field field : fields) {//对于private私有化的成员变量，通过setAccessible来修改器访问权限field.setAccessible(true);if(!validate(field, object, resultInfo)){return resultInfo;};//重新设置会私有权限field.setAccessible(false);}return resultInfo;}/*** 校验bean对象注解* @param field* @param object* @param resultInfo* @throws Exception*/private <T> boolean validate(Field field, T object, BaseResultInfo resultInfo) throws Exception {if(field.isAnnotationPresent(NotNull.class)){NotNull annotation = field.getAnnotation(NotNull.class);if(field.get(object) == null || StringUtils.isBlank(field.get(object).toString())){resultInfo.setCode(ResultCodeEnum.PARAM_ERROR.getCode());resultInfo.setMsg(StringUtils.isEmpty(annotation.message()) ? field.getName()+"不可为空" : annotation.message() );return false;}}if(field.isAnnotationPresent(Date.class)){Date annotation = field.getAnnotation(Date.class);SimpleDateFormat format = new SimpleDateFormat(annotation.format());try {if(field.get(object) != null){format.parse(field.get(object).toString());}} catch (ParseException e) {resultInfo.setCode(ResultCodeEnum.PARAM_ERROR.getCode());resultInfo.setMsg(annotation.message());return false;}}if(field.isAnnotationPresent(Number.class)){Number annotation = field.getAnnotation(Number.class);if(field.get(object) != null){try{new BigDecimal(field.get(object).toString());}catch (Exception e){resultInfo.setCode(ResultCodeEnum.PARAM_ERROR.getCode());resultInfo.setMsg(StringUtils.isEmpty(annotation.message()) ? field.getName()+"必须是数值" : annotation.message() );return false;}}}return true;}}

准备工作做好了接下来看下怎么用
随便定义一个方法的入参,对于thrift等接口，数值类型如果使用double会丢失精度，而且也不支持date类型，所以我们一般都是使用String类型（这里仅仅是参考没有加thrift的相关注解）

import com.api.annotation.Date;
import com.api.annotation.NotNull;
import com.api.annotation.Number;public class ApplyRequest {@NotNullprivate String applyNum;@NotNull(message = "描述不可以为空")private String description;@Numberprivate String amount;@Date(format = "yyyy-MM")private String periodDate;@Dateprivate String creationDate;public String getApplyNum() {return applyNum;}public void setApplyNum(String applyNum) {this.applyNum = applyNum;}public String getAmount() {return amount;}public void setAmount(String amount) {this.amount = amount;}public String getPeriodDate() {return periodDate;}public void setPeriodDate(String periodDate) {this.periodDate = periodDate;}public String getCreationDate() {return creationDate;}public void setCreationDate(String creationDate) {this.creationDate = creationDate;}
}