实现文件上传功能（FileUpload组件）

文件上传：

项目中经常用到文件上传。

自己实现文件上传，使用文件上传组件fileupload组件

1、指定表单类型为文件上传，

enctype=”multipart/form-data”

2、提交方式必须是：post

3、表单中存在文件域元素。

需要的jar包

index.jsp

<body>
    <form action="${pageContext.request.contextPath}/FileUploadTest" method = "post" enctype="multipart/form-data">
        用户名：:<input type = "text" name = "username"/><br>
        文件:<input type = "file" name = "file1"/><br>
        <input type = "submit">
    </form>
</body>

FileUploadTest.servlet

package zck.servlet;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
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.FileItemFactory;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**
 * Servlet implementation class FileUploadTest
 */
@WebServlet("/FileUploadTest")
public class FileUploadTest extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public FileUploadTest() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //创建文件上传工厂类
        DiskFileItemFactory fileItemFactory  =  new DiskFileItemFactory();
        //创建文件上传核心类
        ServletFileUpload upload = new  ServletFileUpload(fileItemFactory);
        upload.setFileSizeMax(30*1024*1024);//设置单个文件最大值30M
        upload.setSizeMax(50*1024*1024);//最多50个文件
        
        //判断表单是否是文件上传表单
            if(upload.isMultipartContent(request)) {
                //把请求数据转化为FileItem对象集合
                try {
                    List<FileItem> list = upload.parseRequest(request);
                    //遍历得到每一个数据项
                    for(FileItem fileItem :list) {
                        //判断普通项，还是文件。
                        if(fileItem.isFormField()) {
                            //普通表单项
                            String fieldName =fileItem.getFieldName();//表单元素名称
                            String content =fileItem.getString();//值
                            System.out.print(fieldName+"\n"+content+"\n\n");
                        }else {
                            //文件上传表单项    
                            String name =fileItem.getName();//获取文件名
                            //上传文件目录路径
                            String basePath = ("D:\\software\\eclipse\\workplace2019-1\\UploadFiles\\WebContent\\upload\\");
                            //新建文件
                            File file = new File(basePath,name);
                            fileItem.write(file);
                            fileItem.delete();//删除临时文件
                        }
                    }
                } catch (FileUploadException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }else {
                System.out.print("不是文件上传表单，不处理");
            }
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

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实现文件上传功能（FileUpload组件）

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