JSP文件上傳 enctype="multipart/form-data"

問題

當上傳文件時，表單需設置 enctype="multipart/form-data"，即：

<form action="UpLoadServlet" method="post" enctype="multipart/form-data">
    ……
</form>

這時如果表單中除了文件，還有其他類型的內容時，Servlet中用request是獲取不到值的。

 

解決

關於表單中只有文件上傳內容的部分見菜鳥教程，這裏不多做贅述。

這裏僅列出主體部分代碼：

picAdd.jsp

<form action="UpLoadServlet" method="post" enctype="multipart/form-data">
    <div class="row form-group">
        <div class="col col-md-2"><label for="text-input" class=" form-control-label">網頁鏈接：</label></div>
        <div class="col-12 col-md-10"><input type="text" name="blogLink" class="form-control"></div>
    </div>
    <div class="row form-group">
        <div class="col col-md-2"><label for="text-input" class=" form-control-label">圖片：</label></div>
        <div class="col-12 col-md-10"><input type="file" name="picLink" ></div>
    </div>
    <div class="row form-group">
        <div class="col col-md-2"><label for="text-input" class=" form-control-label">主頁顯示的文本：</label></div>
        <div class="col-12 col-md-10"><input type="text" name="viewText" class="form-control"></div>
    </div>
    <div class="row form-group">
        <div class="col col-md-2"><label for="text-input" class=" form-control-label">圖片加載失敗時顯示的內容：</label></div>
        <div class="col-12 col-md-10"><input type="text" name="failText" class="form-control">	</div>
   </div>
   <div class="form-group text-right">
	   <button type="submit" class="btn btn-primary btn-md">
	       <i class="fa fa-dot-circle-o"></i> 保存
	   </button>
   </div>
</form>

 

UpLoadServlet.java

package com.laku.fec.controller;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.ibatis.session.SqlSession;

import com.laku.fec.model.entity.Blog;
import com.laku.fec.model.service.IPersonService;
import com.laku.mybatis.MybatisUtils;

/**
 * Servlet implementation class UploadServlet
 */
@WebServlet("/UploadServlet")
public class UpLoadServlet extends HttpServlet {
	
	private static final long serialVersionUID = 1L;
    
    // 上傳文件存儲目錄
    private static final String UPLOAD_DIRECTORY = "upload";
 
    // 上傳配置
    private static final int MEMORY_THRESHOLD   = 1024 * 1024 * 3;  // 3MB
    private static final int MAX_FILE_SIZE      = 1024 * 1024 * 40; // 40MB
    private static final int MAX_REQUEST_SIZE   = 1024 * 1024 * 50; // 50MB
 
    /**
     * 上傳數據及保存文件
     */
    protected void doPost(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
    	
    	//文件上傳**************************
        // 檢測是否爲多媒體上傳
        if (!ServletFileUpload.isMultipartContent(request)) {
            // 如果不是則停止
            PrintWriter writer = response.getWriter();
            writer.println("Error: 表單必須包含 enctype=multipart/form-data");
            writer.flush();
            return;
        }
 
        // 配置上傳參數
        DiskFileItemFactory factory = new DiskFileItemFactory();
        // 設置內存臨界值 - 超過後將產生臨時文件並存儲於臨時目錄中
        factory.setSizeThreshold(MEMORY_THRESHOLD);
        // 設置臨時存儲目錄
        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));
 
        ServletFileUpload upload = new ServletFileUpload(factory);
         
        // 設置最大文件上傳值
        upload.setFileSizeMax(MAX_FILE_SIZE);
         
        // 設置最大請求值 (包含文件和表單數據)
        upload.setSizeMax(MAX_REQUEST_SIZE);
        
        // 中文處理
        upload.setHeaderEncoding("UTF-8"); 

        // 構造臨時路徑來存儲上傳的文件
        // 這個路徑相對當前應用的目錄
        String uploadPath = getServletContext().getRealPath("/") + File.separator + UPLOAD_DIRECTORY;
        System.out.println("1:"+getServletContext().getRealPath("/"));
        System.out.println("2:"+File.separator);
        System.out.println("uploadPath:"+uploadPath);
         
        // 如果目錄不存在則創建
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }
        
        //表單的其他參數
        String blogLink="";//1
        String filePath="";//2
        String viewText="";//3
        String failText="";//4
        
        try {
            // 解析請求的內容提取文件數據
            @SuppressWarnings("unchecked")
            List<FileItem> formItems = upload.parseRequest(request);
             
            if (formItems != null && formItems.size() > 0) {
                // 迭代表單數據
            	int cnt = 0;
                for (FileItem item : formItems) {
                	cnt++;
                    // 處理不在表單中的字段（處理文件）
                    if (!item.isFormField()) {
                        String fileName = new File(item.getName()).getName();
                        filePath = uploadPath + File.separator + fileName;
                        File storeFile = new File(filePath);
                        // 在控制檯輸出文件的上傳路徑
                        System.out.println("filePath:"+filePath);
                        // 保存文件到硬盤
                        item.write(storeFile);
                        request.setAttribute("message",
                            "文件上傳成功!");
                    }else{//處理表單中的非文件
                    	//獲取value值
                    	if(cnt==1) blogLink=item.getString("UTF-8");
                    	else if(cnt==3) viewText=item.getString("UTF-8");
                    	else if(cnt==4) failText=item.getString("UTF-8");
                    	System.out.println("blogLink:"+blogLink);
                    	System.out.println("viewText:"+viewText);
                    	System.out.println("failText:"+failText);
                    }
                }
            }
        } catch (Exception ex) {
            request.setAttribute("message",
                    "錯誤信息: " + ex.getMessage());
        }
        
        //其餘表單內容處理**************************

        SqlSession sqlSession = MybatisUtils.getSqlSession();
    	IPersonService service = sqlSession.getMapper(IPersonService.class);
    	 //中文編碼
      	response.setContentType("text/html;charset=gb2312");
        //封裝和提交
        Blog b = new Blog(blogLink, filePath, viewText, failText);
        int i = service.addPic(b);
        sqlSession.commit();
        
        // 跳轉
        if(i>0){
        	response.getWriter().println("<script> type='text/javascript'>window.alert('輪播圖添加成功！');window.location.href='BackServlet?method=findBlog';</script>");
        }else{
        	response.getWriter().println("<script> type='text/javascript'>window.alert('添加失敗！');window.location.href='backStage/picAdd.jsp';</script>");
        }
    }

}

其中第86-90，113-121行爲非文件表單處理的部分。