自定义注解

首先定义注解类：

import java.lang.annotation.*; @Documented @Target(ElementType.METHOD) @Retention(RetentionPolicy.RUNTIME) public @interface Token {
boolean save() default  false;
boolean remove() default false ;

}

该注解类定义了两个方法，save与remove，其作用在后面的示例中可以看到。下面是该注解应用的拦截器：

import com.jd.fastjson.JSON;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;
public class TokenInterceptor extends HandlerInterceptorAdapter {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
if (handler instanceof HandlerMethod) {
HandlerMethod handlerMethod = (HandlerMethod) handler;
Method method = handlerMethod.getMethod();
Token annotation = method.getAnnotation(Token.class);
if (annotation != null) {
boolean needSaveSession = annotation.save();
if (needSaveSession) {
request.getSession(false).setAttribute("token", UUID.randomUUID().toString());
}
boolean needRemoveSession = annotation.remove();
if (needRemoveSession) {
if (isRepeatSubmit(request)) {
Map map = new HashMap();
map.put("message","请勿频繁提交！");
map.put("error","2");
try {
PrintWriter printWriter = response.getWriter();
printWriter.println(JSON.toJSONString(map));
} catch (IOException e) {
e.printStackTrace();
}
return false;
}
request.getSession(false).removeAttribute("token");
}
}
return true;
} else {
try {
return super.preHandle(request, response, handler);
} catch (Exception e) {
e.printStackTrace();
}
}
return false;
}

private boolean isRepeatSubmit(HttpServletRequest request) {
String serverToken = (String) request.getSession(false).getAttribute("token");
if (serverToken == null) {
return true;
}
String clinetToken = "";
if (request.getMethod().equals("GET")) {
clinetToken = request.getParameter("token");
} else if (request.getMethod().equals("POST")) {
clinetToken = request.getParameter("token");
}
if (clinetToken == null) {
return true;
}
if (!serverToken.equals(clinetToken)) {
return true;
}
return false;
}
}

上面的拦截器是实现拦截所有请求，如果请求的方法上面有Token的注解，则判断是否是save，如果是save，则在session中存入一个token值并传值给页面，这是一个特殊值，用于标示是否是首次请求。如果是remove，则判断页面传回来的token值是否与session中的值相同。首次请求肯定是相同的，首次请求过后会执行session对token属性的删除，这样第二次请求时，页面有token值，而session没有，二者对比不相等，就能判断出这是重复的请求，会传给页面一个提示。

页面的ajax请求的提示如下：

$.ajax({
url: "/xxxxxController/xxxxxMethod?token="+$("input[name=token]").val(),
type: 'post',
data: JSON.stringify({"param":param}),
cache: true,
contentType: "application/json; charset=utf-8",
dataType: 'json',
success: function (data) {
if (data.error == 0) {
window.location.href = "/xxxxxxController/xxxxxMethod";
}else if(data.error ==2){
alert(data.message);
} else {
alert(data.errMsg);
}
},
error: function (XMLHttpRequest, textStatus, errorThrown) {
alert("操作异常");
window.location.href = "/xxxxxxController/xxxxxMethod";
}
});

注解在应用中的代码如下：

第一段代码（访问页面）：

@RequestMapping(value = "audit", method = RequestMethod.POST)
@Token(save = true)
public String toStrategyAudit(Model model, @RequestParam String param) {
JSONObject params = JSONObject.parseObject(param);
String detailId = params.getString("param");
························省略······················································································
model.addAttribute("detailId", detailId);
return "page/xxxxJsp";
}

第二段代码（页面提交请求）：

@RequestMapping(value = "addTable", method = RequestMethod.POST)
@ResponseBody
@Token(remove = true)
public JSONObject saveTableStructure(@RequestBody String body) {
try{
JSONObject result = new JSONObject();
JSONObject bodyJson = JSONObject.parseObject(body);
String paramS = bodyJson.getString("tableStructures");
········································省略···························································
tableMapper.addTable(list);
result.put("error", "0");
}catch(Exception e) {
e.printStackTrace();
result.put("errMsg", "error");
result.put("error", 1);
}
return result;
}

整个拦截器类是为了防止用户点击提交太频繁，导致后台提交的代码执行多次，会产生很严重的错误。