java文件上传时如何处理参数

ゝ一世哀愁。 2021-10-18 15:26 538阅读 0赞

1.准备工作  
需要的jar包：common-fileupload.jar 和 common-io.jar  
下载地址：  
[https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload][https_mvnrepository.com_artifact_commons-fileupload_commons-fileupload]  
[https://mvnrepository.com/artifact/commons-io/commons-io][https_mvnrepository.com_artifact_commons-io_commons-io]  
2.前端测试代码

这里有几点需要注意的：  
1）表单提交方式需要post提交，get提交同样还是普通表单  
2）需要个体enctype指定类型enctype=“multipart/form-data”，表示文件上传表单  
3）上传文件的input的type类型为file类型  
![在这里插入图片描述][20190812170648125.png]  
3.后端代码

package com.web.upload;
    
    import java.io.File;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.List;
    
    import javax.servlet.ServletException;
    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.FileUploadException;
    import org.apache.commons.fileupload.disk.DiskFileItemFactory;
    import org.apache.commons.fileupload.servlet.ServletFileUpload;
    import org.apache.commons.io.IOUtils;
    
    public class FileUploadServlet extends HttpServlet {
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException {
    		//1.创建磁盘文件项工厂对象
    		DiskFileItemFactory factory = new DiskFileItemFactory();
    		factory.setSizeThreshold(1024*1024);//设置缓冲区大小，单位字节，当上传文件大小超过缓冲区大小会产生临时文件
    		String tempPath = this.getServletContext().getRealPath("temp");//获取临时文件夹绝对路径
    		factory.setRepository(new File(tempPath));//设置临时文件夹
    		//2.创建文件上传核心类
    		ServletFileUpload upload = new ServletFileUpload(factory);
    		boolean multipartContent = upload.isMultipartContent(request);//是否为文件上传表单，是返回true，不是返回false
    		if(multipartContent){
    			//文件上传表单，即enctype="multipart/form-data"，request.getParameter相关方法失效，无法获取文件上传表单参数的值
    			try {
    				upload.setHeaderEncoding("utf-8");//防止文件上传乱码
    				//3.解析request,获取文件项集合
    				List<FileItem> parseRequest = upload.parseRequest(request);
    				System.out.println("文件上传表单--------");
    				//4.遍历文件项集合
    				for (FileItem fileItem : parseRequest) {
    					boolean formField = fileItem.isFormField();//文件项是否未表单项，是返回true，不是返回false
    					if(formField){
    						//普通表单项
    						String fieldName = fileItem.getFieldName();//获取表单项的name
    						String filedValue = fileItem.getString("utf-8");//已utf-8的编码获取表单项的value,防止中文乱码
    						System.out.println(fieldName+":"+filedValue);
    					}else{
    						//文件上传项
    						String fileName = fileItem.getName();//获取文件名
    						InputStream in = fileItem.getInputStream();//文件输入流
    						String path = this.getServletContext().getRealPath("upload");//获取文件存放的绝对目录
    						File file = new File(path+"/"+fileName);
    						FileOutputStream out = new FileOutputStream(file);//获取文件输出流
    						IOUtils.copy(in, out);//拷贝文件到上传目录
    						in.close();
    						out.close();
    						fileItem.delete();//删除临时文件
    					}
    				}
    			} catch (FileUploadException e) {
    				e.printStackTrace();
    			}
    		}else{
    			//普通表单，还是使用request.getParameter等方法
    			request.setCharacterEncoding("utf-8");
    			System.out.println("普通表单--------");
    			String username = request.getParameter("username");
    			String filename = request.getParameter("upload");
    			System.out.println("username:"+username+";filename:"+filename);
    		}
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

[https_mvnrepository.com_artifact_commons-fileupload_commons-fileupload]: https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload
[https_mvnrepository.com_artifact_commons-io_commons-io]: https://mvnrepository.com/artifact/commons-io/commons-io
[20190812170648125.png]: /images/20211018/6df032df86f34058a0c6f1636029ed50.png