在开发中，一个对外暴露的接口可能会面临瞬间的大量重复请求，如果想过滤掉重复请求造成对业务的伤害，那就需要实现幂等
幂等：
任意多次执行所产生的影响均与一次执行的影响相同。最终的含义就是 对数据库的影响只能是一次性的，不能重复处理。
解决方案：
- 数据库建立唯一性索引，可以保证最终插入数据库的只有一条数据
- token机制，每次接口请求前先获取一个token，然后再下次请求的时候在请求的header体中加上这个token，后台进行验证，如果验证通过删除token，下次请求再次判断token（本次案例使用）
- 悲观锁或者乐观锁，悲观锁可以保证每次for update的时候其他sql无法update数据(在数据库引擎是innodb的时候,select的条件必须是唯一索引,防止锁全表)
- 先查询后判断，首先通过查询数据库是否存在数据，如果存在证明已经请求过了，直接拒绝该请求，如果没有存在，就证明是第一次进来，直接放行
一、搭建Redis服务
package com.ckw.idempotence.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.ValueOperations;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import org.springframework.stereotype.Component;
import java.io.Serializable;
import java.util.concurrent.TimeUnit;
@Component
public class RedisService {
private RedisTemplate redisTemplate;
@Autowired(required = false)
public void setRedisTemplate(RedisTemplate redisTemplate) {
RedisSerializer stringSerializer = new StringRedisSerializer();
redisTemplate.setKeySerializer(stringSerializer);
redisTemplate.setValueSerializer(stringSerializer);
redisTemplate.setHashKeySerializer(stringSerializer);
redisTemplate.setHashValueSerializer(stringSerializer);
this.redisTemplate = redisTemplate;
}
public boolean set(final String key, Object value) {
boolean result = false;
try {
ValueOperations operations = redisTemplate.opsForValue();
operations.set(key, value);
result = true;
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
public boolean setEx(final String key, Object value, Long expireTime) {
boolean result = false;
try {
ValueOperations<Serializable, Object> operations = redisTemplate.opsForValue();
operations.set(key, value);
redisTemplate.expire(key, expireTime, TimeUnit.SECONDS);
result = true;
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
public boolean exists(final String key) {
return redisTemplate.hasKey(key);
}
public Object get(final String key) {
Object o = null;
ValueOperations valueOperations = redisTemplate.opsForValue();
return valueOperations.get(key);
}
public Boolean remove(final String key) {
if(exists(key)){
return redisTemplate.delete(key);
}
return false;
}
}二、自定义注解
作用：拦截器拦截请求时，判断调用的地址对应的Controller方法是否有自定义注解，有的话说明该接口方法进行 幂等
package com.ckw.idempotence.annotion;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface AutoIdempotent {
}三、Token创建和校验
package com.ckw.idempotence.service;
import com.ckw.idempotence.exectionhandler.BaseException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.util.StringUtils;
import javax.servlet.http.HttpServletRequest;
import java.util.UUID;
@Service
public class TokenService {
@Autowired RedisService redisService;
//创建token
public String createToken() {
//使用UUID代表token
UUID uuid = UUID.randomUUID();
String token = uuid.toString();
//存入redis
boolean b = redisService.setEx(token, token, 10000L);
return token;
}
//检验请求头或者请求参数中是否有token
public boolean checkToken(HttpServletRequest request) {
String token = request.getHeader("token");
//如果header中是空的
if(StringUtils.isEmpty(token)){
//从request中拿
token = request.getParameter("token");
if(StringUtils.isEmpty(token)){
throw new BaseException(20001, "缺少参数token");
}
}
//如果从header中拿到的token不正确
if(!redisService.exists(token)){
throw new BaseException(20001, "不能重复提交-------token不正确、空");
}
//token正确 移除token
if(!redisService.remove(token)){
throw new BaseException(20001, "token移除失败");
}
return true;
}
}这里用到了自定义异常和自定义响应体如下
自定义异常：
package com.ckw.idempotence.exectionhandler;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@AllArgsConstructor
@NoArgsConstructor
public class BaseException extends RuntimeException {
private Integer code;
private String msg;
}设置统一异常处理：
package com.ckw.idempotence.exectionhandler;
import com.ckw.idempotence.utils.R;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;
@ControllerAdvice
public class GlobalExceptionHandler {
@ExceptionHandler(Exception.class)
@ResponseBody
public R error(Exception e){
e.printStackTrace();
return R.error();
}
@ExceptionHandler(BaseException.class)
@ResponseBody
public R error(BaseException e){
e.printStackTrace();
return R.error().message(e.getMsg()).code(e.getCode());
}
}自定义响应体：
package com.ckw.idempotence.utils;
import lombok.Data;
import java.util.HashMap;
import java.util.Map;
@Data
public class R {
private Boolean success;
private Integer code;
private String message;
private Map<String, Object> data = new HashMap<String, Object>();
private R() {
}
//封装返回成功
public static R ok(){
R r = new R();
r.setSuccess(true);
r.setCode(ResultCode.SUCCESS);
r.setMessage("成功");
return r;
}
//封装返回失败
public static R error(){
R r = new R();
r.setSuccess(false);
r.setCode(ResultCode.ERROR);
r.setMessage("失败");
return r;
}
public R success(Boolean success){
this.setSuccess(success);
return this;
}
public R message(String message){
this.setMessage(message);
return this;
}
public R code(Integer code){
this.setCode(code);
return this;
}
public R data(String key, Object value){
this.data.put(key, value);
return this;
}
public R data(Map<String, Object> map){
this.setData(map);
return this;
}
}
自定义响应码：
package com.ckw.idempotence.utils;
import lombok.Data;
import java.util.HashMap;
import java.util.Map;
@Data
public class R {
private Boolean success;
private Integer code;
private String message;
private Map<String, Object> data = new HashMap<String, Object>();
private R() {
}
//封装返回成功
public static R ok(){
R r = new R();
r.setSuccess(true);
r.setCode(ResultCode.SUCCESS);
r.setMessage("成功");
return r;
}
//封装返回失败
public static R error(){
R r = new R();
r.setSuccess(false);
r.setCode(ResultCode.ERROR);
r.setMessage("失败");
return r;
}
public R success(Boolean success){
this.setSuccess(success);
return this;
}
public R message(String message){
this.setMessage(message);
return this;
}
public R code(Integer code){
this.setCode(code);
return this;
}
public R data(String key, Object value){
this.data.put(key, value);
return this;
}
public R data(Map<String, Object> map){
this.setData(map);
return this;
}
}
四、拦截器配置
1、拦截器配置类
package com.ckw.idempotence.config;
import com.ckw.idempotence.interceptor.AutoIdempotentInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
@Configuration
public class WebConfiguration implements WebMvcConfigurer {
@Autowired
private AutoIdempotentInterceptor autoIdempotentInterceptor;
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(autoIdempotentInterceptor);
}
}
2、拦截器类
package com.ckw.idempotence.interceptor;
import com.ckw.idempotence.annotion.AutoIdempotent;
import com.ckw.idempotence.service.TokenService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Method;
@Component
public class AutoIdempotentInterceptor implements HandlerInterceptor {
@Autowired
private TokenService tokenService;
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
if(!(handler instanceof HandlerMethod))
return true;
HandlerMethod handlerMethod = (HandlerMethod) handler;
Method method = handlerMethod.getMethod();
//拿到方法上面的自定义注解
AutoIdempotent annotation = method.getAnnotation(AutoIdempotent.class);
//如果不等于null说明该方法要进行幂等
if(null != annotation){
return tokenService.checkToken(request);
}
return true;
}
}
五、正常Sevice类
package com.ckw.idempotence.service;
import org.springframework.stereotype.Service;
@Service
public class TestService {
public String testMethod(){
return "正常业务逻辑";
}
}
六、Controller类
package com.ckw.idempotence.controller;
import com.ckw.idempotence.annotion.AutoIdempotent;
import com.ckw.idempotence.service.TestService;
import com.ckw.idempotence.service.TokenService;
import com.ckw.idempotence.utils.R;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
@RestController
@CrossOrigin
@RequestMapping("/Idempotence")
public class TestController {
@Autowired
private TokenService tokenService;
@Autowired
private TestService testService;
@GetMapping("/getToken")
public R getToken(){
String token = tokenService.createToken();
return R.ok().data("token",token);
}
//相当于添加数据接口（测试时 连续点击添加数据按钮 看结果是否是添加一条数据还是多条数据）
@AutoIdempotent
@PostMapping("/test/addData")
public R addData(){
String s = testService.testMethod();
return R.ok().data("data",s);
}
}七、测试
第一次点击：
第二次点击：
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