FileUpload 核心API介绍--ServletFileUpload 讲解

艾米莉亚糖

已于 2022-05-03 15:27:10 修改

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分类专栏： § -- JavaEE 文章标签：原创

于 2018-07-06 17:13:41 首次发布

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ServletFileUpload的讲解.

1.ServletFileUpload upload=new ServletFileUpload(factory);

创建一个上传工具，指定使用缓存区与临时文件存储位置.

2.List<FileItem> items=upload.parseRequest(request);

它是用于解析request对象，得到所有上传项.每一个FileItem就相当于一个上传项.

3.boolean flag=upload.isMultipartContent(request);

用于判断是否是上传.

可以简单理解，就是判断encType="multipart/form-data";

4.设置上传文件大小.

void setFileSizeMax(long fileSizeMax) 设置单个文件上传大小 .

void setSizeMax(long sizeMax) 设置总文件上传大小 .

5.解决上传文件中文名称乱码.

setHeaderEncoding("utf-8");

注意:如果使用reqeust.setCharacterEncoding("utf-8")也可以，但不建议使用。

代码实现:

在javaweb文件上传(2) 的基础上新建一个Servlet文件,名字为Upload3Servlet.java,代码如下所示.

package cn.itcast.web.servlet;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
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;

//commons-fileupload api详解
@SuppressWarnings("all")
public class Upload3Servlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");

		// 1.创建 DiskFileItemFactory
		// DiskFileItemFactory factory = new DiskFileItemFactory(); //使用默认的.
		File file = new File(this.getServletContext().getRealPath("/temp"));// 获取temp目录部署到tomcat后的绝对磁盘路径
		DiskFileItemFactory factory = new DiskFileItemFactory(1024 * 100, file); // 使用默认的.

		// 2.创建ServletFileUpload
		ServletFileUpload upload = new ServletFileUpload(factory);
		boolean flag = upload.isMultipartContent(request); // 用于判断是否是上传操作.

			// 解决上传文件名称的中文乱码
			upload.setHeaderEncoding("utf-8");
			try {
				List<FileItem> items = upload.parseRequest(request);// 解决request,得到所有的上传项FileItem
			    }
			} catch (FileUploadException e) {
				e.printStackTrace();
			}
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}
}

upload2.jsp页面.

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'index.jsp' starting page</title>
  </head>
  <body>
	<form action="${pageContext.request.contextPath}/upload2" method="post" encType="multipart/form-data">
		<input type="text" name="content"><br>
		<input type="file" name="f"><br>
		<input type="submit" value="上传">
	</form>
  </body>
</html>

web.xml文件如下.

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
  <display-name></display-name>
  <servlet>
    <servlet-name>Upload1Servlet</servlet-name>
    <servlet-class>cn.itcast.web.servlet.Upload1Servlet</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>Upload2Servlet</servlet-name>
    <servlet-class>cn.itcast.web.servlet.Upload2Servlet</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>Upload3Servlet</servlet-name>
    <servlet-class>cn.itcast.web.servlet.Upload3Servlet</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>Upload4Servlet</servlet-name>
    <servlet-class>cn.itcast.web.servlet.Upload4Servlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>Upload1Servlet</servlet-name>
    <url-pattern>/upload1</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>Upload2Servlet</servlet-name>
    <url-pattern>/upload2</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>Upload3Servlet</servlet-name>
    <url-pattern>/upload3</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>Upload4Servlet</servlet-name>
    <url-pattern>/upload4</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

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FileUpload 核心API介绍--ServletFileUpload 讲解

ServletFileUpload的讲解.1.ServletFileUpload upload=new ServletFileUpload(factory);创建一个上传工具，指定使用缓存区与临时文件存储位置.2.List&lt;FileItem&gt; items=upload.parseRequest(request)...
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