使用自定义注解实现防止表单重复提交

我们还是先引入 Maven 依赖

<!-- Spring框架基本的核心工具 -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context-support</artifactId>
</dependency>

<!-- SpringWeb模块 -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-web</artifactId>
</dependency>
<!-- 自定义验证注解 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>
<!--常用工具类 -->
<dependency>
    <groupId>org.Apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
</dependency>
<!-- io常用工具类 -->
<dependency>
     <groupId>commons-io</groupId>
     <artifactId>commons-io</artifactId>
 </dependency>
<!-- JSON工具类 -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
</dependency>
<!-- 阿里JSON解析器 -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
</dependency>
<!-- servlet包 -->
<dependency>
    <groupId>JAVAx.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
</dependency>
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接下来我们实现一个注解类（注解在 Java 中与类、接口的声明类似，只是所使用的关键字有所不同，声明注解使用 @interface 关键字。在底层实现上，所有定义的注解都会自动继承
java.lang.annotation.Annotation 接口。）

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 自定义注解防止表单重复提交
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RepeatSubmit
{
    /**
     * 间隔时间(ms)，小于此时间视为重复提交
     */
    public int interval() default 5000;

    /**
     * 提示消息
     */
    public String message() default "不允许重复提交，请稍后再试";
}
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P.S. 关于自定义注解的解释在之前的博客中有写到，这里就不再多说了，有需要了解的小伙伴请移步至：大聪明教你学Java | Spring Boot 使用自定义注解实现操作日志的记录

下面我们再实现一个拦截器，对提交表单的过程做一个相应的拦截校验

import java.lang.reflect.Method;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;

/**
 * 防止重复提交拦截器
 */
@Component
public abstract class RepeatSubmitInterceptor implements HandlerInterceptor
{
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception
    {
        if (handler instanceof HandlerMethod)
        {
            HandlerMethod handlerMethod = (HandlerMethod) handler;
            Method method = handlerMethod.getMethod();
            RepeatSubmit annotation = method.getAnnotation(RepeatSubmit.class);
            if (annotation != null)
            {
                if (this.isRepeatSubmit(request, annotation))
                {
                    //如果本次提交被认为是重复提交，则在此处做具体的逻辑处理
                    //如：弹出警告窗口等
                    return false;
                }
            }
            return true;
        }
        else
        {
            return true;
        }
    }

    /**
     * 验证是否重复提交由子类实现具体的防重复提交的规则
     *
     * @param request 请求对象
     * @param annotation 防复注解
     * @return 结果
     */
    public abstract boolean isRepeatSubmit(HttpServletRequest request, RepeatSubmit annotation) throws Exception;
}
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我们可以看到再拦截器中一共有两个方法，分别是 preHandle 和 isRepeatSubmit。无论我们执行什么请求，都会进入 RepeatSubmitInterceptor 拦截器，进入拦截器后先执行 preHandle 方法进行预处理，判断本次拦截的方法是否增加了 RepeatSubmit 自定义注解，如果增加了该注解才会进行具体的校验。isRepeatSubmit 方法是防止表单重复提交的规则，我们通过子类来实现 isRepeatSubmit 具体的校验规则

import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import com.mumu.framework.interceptor.RepeatSubmitInterceptor;
import org.springframework.stereotype.Component;
import com.mumu.common.annotation.RepeatSubmit;
import com.xxx.xxx.xxx.JSON; 

/**
 * 判断请求url和数据是否和上一次相同
 * com.xxx.xxx.xxx.JSON; 是自定义的json工具类，具体代码贴在后面
 */
@Component
public class SameUrlDataInterceptor extends RepeatSubmitInterceptor
{
    public final String REPEAT_PARAMS = "repeatParams";

    public final String REPEAT_TIME = "repeatTime";

    public final String SESSION_REPEAT_KEY = "repeatData";

    @SuppressWarnings("unchecked")
    @Override
    public boolean isRepeatSubmit(HttpServletRequest request, RepeatSubmit annotation) throws Exception
    {
        // 本次参数及系统时间
        String nowParams = JSON.marshal(request.getParameterMap());
        Map<String, Object> nowDataMap = new HashMap<String, Object>();
        nowDataMap.put(REPEAT_PARAMS, nowParams);
        nowDataMap.put(REPEAT_TIME, System.currentTimeMillis());

        // 请求地址（作为存放session的key值）
        String url = request.getRequestURI();

        HttpSession session = request.getSession();
        Object sessionObj = session.getAttribute(SESSION_REPEAT_KEY);
        if (sessionObj != null)
        {
            Map<String, Object> sessionMap = (Map<String, Object>) sessionObj;
            if (sessionMap.containsKey(url))
            {
                Map<String, Object> preDataMap = (Map<String, Object>) sessionMap.get(url);
                if (compareParams(nowDataMap, preDataMap) && compareTime(nowDataMap, preDataMap, annotation.interval()))
                {
                    return true;
                }
            }
        }
        Map<String, Object> sessionMap = new HashMap<String, Object>();
        sessionMap.put(url, nowDataMap);
        session.setAttribute(SESSION_REPEAT_KEY, sessionMap);
        return false;
    }

    /**
     * 判断参数是否相同
     */
    private boolean compareParams(Map<String, Object> nowMap, Map<String, Object> preMap)
    {
        String nowParams = (String) nowMap.get(REPEAT_PARAMS);
        String preParams = (String) preMap.get(REPEAT_PARAMS);
        return nowParams.equals(preParams);
    }

    /**
     * 判断两次间隔时间
     */
    private boolean compareTime(Map<String, Object> nowMap, Map<String, Object> preMap, int interval)
    {
        long time1 = (Long) nowMap.get(REPEAT_TIME);
        long time2 = (Long) preMap.get(REPEAT_TIME);
        if ((time1 - time2) < interval)
        {
            return true;
        }
        return false;
    }
}
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自定义 Json 工具类

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMAppingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectWriter;

/**
 * JSON解析处理
 */
public class JSON
{
    private static final ObjectMapper objectMapper = new ObjectMapper();
    private static final ObjectWriter objectWriter = objectMapper.writerWithDefaultPrettyPrinter();

    public static void marshal(File file, Object value) throws Exception
    {
        try
        {
            objectWriter.writeValue(file, value);
        }
        catch (JsonGenerationException e)
        {
            throw new Exception(e);
        }
        catch (JsonMappingException e)
        {
            throw new Exception(e);
        }
        catch (IOException e)
        {
            throw new Exception(e);
        }
    }

    public static void marshal(OutputStream os, Object value) throws Exception
    {
        try
        {
            objectWriter.writeValue(os, value);
        }
        catch (JsonGenerationException e)
        {
            throw new Exception(e);
        }
        catch (JsonMappingException e)
        {
            throw new Exception(e);
        }
        catch (IOException e)
        {
            throw new Exception(e);
        }
    }

    public static String marshal(Object value) throws Exception
    {
        try
        {
            return objectWriter.writeValueAsString(value);
        }
        catch (JsonGenerationException e)
        {
            throw new Exception(e);
        }
        catch (JsonMappingException e)
        {
            throw new Exception(e);
        }
        catch (IOException e)
        {
            throw new Exception(e);
        }
    }

    public static byte[] marshalBytes(Object value) throws Exception
    {
        try
        {
            return objectWriter.writeValueAsBytes(value);
        }
        catch (JsonGenerationException e)
        {
            throw new Exception(e);
        }
        catch (JsonMappingException e)
        {
            throw new Exception(e);
        }
        catch (IOException e)
        {
            throw new Exception(e);
        }
    }

    public static <T> T unmarshal(File file, Class<T> valueType) throws Exception
    {
        try
        {
            return objectMapper.readValue(file, valueType);
        }
        catch (JsonParseException e)
        {
            throw new Exception(e);
        }
        catch (JsonMappingException e)
        {
            throw new Exception(e);
        }
        catch (IOException e)
        {
            throw new Exception(e);
        }
    }

    public static <T> T unmarshal(InputStream is, Class<T> valueType) throws Exception
    {
        try
        {
            return objectMapper.readValue(is, valueType);
        }
        catch (JsonParseException e)
        {
            throw new Exception(e);
        }
        catch (JsonMappingException e)
        {
            throw new Exception(e);
        }
        catch (IOException e)
        {
            throw new Exception(e);
        }
    }

    public static <T> T unmarshal(String str, Class<T> valueType) throws Exception
    {
        try
        {
            return objectMapper.readValue(str, valueType);
        }
        catch (JsonParseException e)
        {
            throw new Exception(e);
        }
        catch (JsonMappingException e)
        {
            throw new Exception(e);
        }
        catch (IOException e)
        {
            throw new Exception(e);
        }
    }

    public static <T> T unmarshal(byte[] bytes, Class<T> valueType) throws Exception
    {
        try
        {
            if (bytes == null)
            {
                bytes = new byte[0];
            }
            return objectMapper.readValue(bytes, 0, bytes.length, valueType);
        }
        catch (JsonParseException e)
        {
            throw new Exception(e);
        }
        catch (JsonMappingException e)
        {
            throw new Exception(e);
        }
        catch (IOException e)
        {
            throw new Exception(e);
        }
    }
}

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在校验的过程中主要针对三个部分做校验：请求地址、请求参数以及请求时间，只有当请求地址和请求参数一致且两次请求的时间间隔小于xx毫秒时（xx毫秒即为在自定义注解中指定的时间），才会被判定为是重复提交。这种校验方式较为繁琐（毕竟需要比对三部分内容），但是它可以尽可能的避免出现“误拦截”的情况，让系统有更高的可用性和安全性。

本文中提到的方法只是众多方法中的一种，我个人也是通过这种方式来实现的防止表单重复提交。当然了，我们可以选择的办法有很多，比如采用 JS 禁用提交按钮、利用Session防止表单重复提交等等，最终如何选择还是要根据自己的应用和开发框架来决定，选择一个适合自己的方法才是最好的。