struts2 使用 jakarta 上传文件时commons fileupload的异常捕捉

问题：

        struts2 使用jakarta 上传文件时，如果上传文件的大小超出commons fileupload(jakarta上传文件还是依赖commons-fileupload)设置的大小就会在进入action以前抛出异常.
        如果想返回用户的输入界面（input）,那么页面原来的参数会丢失。

首先看一下struts2 执行一个action的过程

1.  将用户请求发给org.apache.struts2.dispatcher.Dispatcher，
     wrapRequest(HttpServletRequest request, ServletContext servletContext)  方法会判断是否"multipart/form-data"，如果是建立一个multiPartRequest 的实例，并且建立MultiPartRequestWrapper

写道

...if (content_type != null && content_type.indexOf("multipart/form-data") != -1) {
       MultiPartRequest multi = getContainer().getInstance(MultiPartRequest.class);
       request = new MultiPartRequestWrapper(multi, request, getSaveDir(servletContext));
} else {
       request = new StrutsRequestWrapper(request);
}

 

2. 建立 MultiPartRequestWrapper 时解析(parse) request,

public void parse(HttpServletRequest servletRequest, String saveDir)
            throws IOException {
        DiskFileItemFactory fac = new DiskFileItemFactory();
        // Make sure that the data is written to file
        fac.setSizeThreshold(0);
        if (saveDir != null) {
            fac.setRepository(new File(saveDir));
        }

        // Parse the request
        try {
            ServletFileUpload upload = new ServletFileUpload(fac);
            upload.setSizeMax(maxSize);
            //upload 解析request并取得页面参数
        List items = upload.parseRequest(createRequestContext(servletRequest));
        ......

 3.我们看一下ServletFileUpload(commons-fileupload v1.1.1) 的parseRequest做了什么

public List /* FileItem */ parseRequest(RequestContext ctx)
           throws FileUploadException {
       if (ctx == null) {
           throw new NullPointerException("ctx parameter");
       }

       ArrayList items = new ArrayList();
       String contentType = ctx.getContentType();

       if ((null == contentType)
           || (!contentType.toLowerCase().startsWith(MULTIPART))) {
           throw new InvalidContentTypeException(
               "the request doesn't contain a "
               + MULTIPART_FORM_DATA
               + " or "
               + MULTIPART_MIXED
               + " stream, content type header is "
               + contentType);
       }
       int requestSize = ctx.getContentLength();

       if (requestSize == -1) {
           throw new UnknownSizeException(
               "the request was rejected because its size is unknown");
       }
       //关键就这里了，大小超出的异常，这里是所有上传文件合计的大小，如果超出就抛出异常
       //这时上层是拿不到保存参数的items的
       if (sizeMax >= 0 && requestSize > sizeMax) {
           throw new SizeLimitExceededException(
               "the request was rejected because its size (" + requestSize
               + ") exceeds the configured maximum (" + sizeMax + ")",
               requestSize, sizeMax);
       }

       String charEncoding = headerEncoding;
       if (charEncoding == null) {
           charEncoding = ctx.getCharacterEncoding();
       }

       try {
           byte[] boundary = getBoundary(contentType);
           if (boundary == null) {
               throw new FileUploadException(
                       "the request was rejected because "
                       + "no multipart boundary was found");
           }

           InputStream input = ctx.getInputStream();

           MultipartStream multi = new MultipartStream(input, boundary);
           multi.setHeaderEncoding(charEncoding);

           boolean nextPart = multi.skipPreamble();
           while (nextPart) {
               Map headers = parseHeaders(multi.readHeaders());
               String fieldName = getFieldName(headers);
               if (fieldName != null) {
                   String subContentType = getHeader(headers, CONTENT_TYPE);
                   if (subContentType != null && subContentType
                       .toLowerCase().startsWith(MULTIPART_MIXED)) {
                       // Multiple files.
                       byte[] subBoundary = getBoundary(subContentType);
                       multi.setBoundary(subBoundary);
                       boolean nextSubPart = multi.skipPreamble();
                       while (nextSubPart) {
                           headers = parseHeaders(multi.readHeaders());
                           if (getFileName(headers) != null) {
                               FileItem item =
                                       createItem(headers, false);
                               OutputStream os = item.getOutputStream();
                               try {
                                   multi.readBodyData(os);
                               } finally {
                                   os.close();
                               }
                               items.add(item);
                           } else {
                               // Ignore anything but files inside
                               // multipart/mixed.
                               multi.discardBodyData();
                           }
                           nextSubPart = multi.readBoundary();
                       }
                       multi.setBoundary(boundary);
                   } else {
                       FileItem item = createItem(headers,
                               getFileName(headers) == null);
                       OutputStream os = item.getOutputStream();
                       try {
                           multi.readBodyData(os);
                       } finally {
                           os.close();
                       }
                       items.add(item);
                   }
               } else {
                   // Skip this part.
                   multi.discardBodyData();
               }
               nextPart = multi.readBoundary();
           }
       } catch (IOException e) {
           throw new FileUploadException(
               "Processing of " + MULTIPART_FORM_DATA
                   + " request failed. " + e.getMessage());
       }

       return items;
   }

 4.这之后才开始逐个进入interceptor,见DefaultActionInvocation.invoke()

....
//递归interceptor
if (interceptors.hasNext()) {
                final InterceptorMapping interceptor = (InterceptorMapping) interceptors.next();
                UtilTimerStack.profile("interceptor: "+interceptor.getName(),
                        new UtilTimerStack.ProfilingBlock<String>() {
                            public String doProfiling() throws Exception {
                                resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);
                                return null;
                            }
                });
            } else {
                        //如果有errors,resultCode会得到‘input’
                resultCode = invokeActionOnly();
            }
...

 5.我们的目标就是返回input并且保留页面原来的参数，那么就要不要让ServletFileUpload抛出异常，并且要让strusts使用我们自己的jakart.

 6.写自己的ServletFileUpload

/*
 * Copyright 2001-2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.infowarelab.newcentury.web.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.FileUpload;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.MultipartStream;
import org.apache.commons.fileupload.RequestContext;
import org.apache.commons.fileupload.servlet.ServletRequestContext;
import org.apache.log4j.Logger;

/**
  * come from commons-fileupload
  * @author alfred
 */
public class ServletFileUpload extends FileUpload {

    // ---------------------------------------------------------- Class methods

    /**
     * Logger for this class
     */
    private static final Logger logger = Logger.getLogger(ServletFileUpload.class);
    private List<String> errors = new ArrayList<String>();

    /**
     * Constructs an uninitialised instance of this class. A factory must be
     * configured, using <code>setFileItemFactory()</code>, before attempting
     * to parse requests.
     *
     * @see FileUpload#FileUpload(FileItemFactory)
     */
    public ServletFileUpload() {
        super();
    }

    /**
     * Constructs an instance of this class which uses the supplied factory to
     * create <code>FileItem</code> instances.
     *
     * @see FileUpload#FileUpload()
     */
    public ServletFileUpload(FileItemFactory fileItemFactory) {
        super(fileItemFactory);
    }
    /**
     * overide parseRequest
     */
    public List /* FileItem */parseRequest(RequestContext ctx) throws FileUploadException {
        if (ctx == null) {
            throw new NullPointerException("ctx parameter");
        }

        ArrayList items = new ArrayList();
        String contentType = ctx.getContentType();

        if ((null == contentType) || (!contentType.toLowerCase().startsWith(MULTIPART))) {
            throw new InvalidContentTypeException("the request doesn't contain a " + MULTIPART_FORM_DATA + " or "
                    + MULTIPART_MIXED + " stream, content type header is " + contentType);
        }
        int requestSize = ctx.getContentLength();

        if (requestSize == -1) {
            // throw new UnknownSizeException(
            // "the request was rejected because its size is unknown");
            logger.error("the request was rejected because its size is unknown");
            errors.add("the request was rejected because its size is unknown");
        }

        String charEncoding = getHeaderEncoding();
        if (charEncoding == null) {
            charEncoding = ctx.getCharacterEncoding();
        }

        try {
            byte[] boundary = getBoundary(contentType);
            if (boundary == null) {
                // throw new FileUploadException(
                // "the request was rejected because "
                // + "no multipart boundary was found");
                logger.error("the request was rejected because no multipart boundary was found");
                errors.add("the request was rejected because no multipart boundary was found");
            }

            InputStream input = ctx.getInputStream();

            MultipartStream multi = new MultipartStream(input, boundary);
            multi.setHeaderEncoding(charEncoding);

            boolean nextPart = multi.skipPreamble();
            while (nextPart) {
                Map headers = parseHeaders(multi.readHeaders());
                String fieldName = getFieldName(headers);
                if (fieldName != null) {
                    String subContentType = getHeader(headers, CONTENT_TYPE);
                    if (subContentType != null && subContentType.toLowerCase().startsWith(MULTIPART_MIXED)) {
                        // Multiple files.
                        byte[] subBoundary = getBoundary(subContentType);
                        multi.setBoundary(subBoundary);
                        boolean nextSubPart = multi.skipPreamble();
                        while (nextSubPart) {
                            headers = parseHeaders(multi.readHeaders());
                            if (getFileName(headers) != null) {
                                FileItem item = createItem(headers, false);
                                OutputStream os = item.getOutputStream();
                                try {
                                    multi.readBodyData(os);
                                } finally {
                                    os.close();
                                }
                                items.add(item);
                            } else {
                                // Ignore anything but files inside
                                // multipart/mixed.
                                multi.discardBodyData();
                            }
                            nextSubPart = multi.readBoundary();
                        }
                        multi.setBoundary(boundary);
                    } else {
                        FileItem item = createItem(headers, getFileName(headers) == null);
                        OutputStream os = item.getOutputStream();
                        try {
                            multi.readBodyData(os);
                        } finally {
                            os.close();
                        }
                        items.add(item);
                    }
                } else {
                    // Skip this part.
                    multi.discardBodyData();
                }
                nextPart = multi.readBoundary();
            }
            // remove SizeLimitExceededException
            if (getSizeMax() >= 0 && requestSize > getSizeMax()) {
                // throw new SizeLimitExceededException(
                // "the request was rejected because its size (" + requestSize
                // + ") exceeds the configured maximum (" + getSizeMax() + ")",
                // requestSize, getSizeMax());
                logger.error("the request was rejected because its size (" + requestSize
                        + ") exceeds the configured maximum (" + getSizeMax() + ")");
            }
        } catch (IOException e) {
            logger.error("Processing of " + MULTIPART_FORM_DATA + " request failed. " + e.getMessage());
            errors.add("Processing of " + MULTIPART_FORM_DATA + " request failed. " + e.getMessage());
            // throw new FileUploadException(
            // "Processing of " + MULTIPART_FORM_DATA
            // + " request failed. " + e.getMessage());
        }

        return items;
    }

    /**
     * @return the errors
     */
    public List<String> getErrors() {
        return errors;
    }

    /**
     * @param errors the errors to set
     */
    public void setErrors(List<String> errors) {
        this.errors = errors;
    }

}

 

7.copy org.apache.struts2.dispatcher.multipart.JakartaMultiPartRequest，只是import上面自己的ServletFileUpload.这样就可以保存页面的所有参数了。

8.更改struts配置文件加入你自己的JakartaMultiReques

<bean type="org.apache.struts2.dispatcher.multipart.MultiPartRequest"
ame="jakarta_yourself"
       class="com.xxxxx.util.JakartaMultiPartRequest"
cope="default" optional="true" />

 9.更改struts.properties

struts.multipart.parser=jakarta_yourself

10.就OK啦