原生Servlet 上传文件

依赖jar

        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.4</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>

示例如下：

1.   新建Maven项目  upload

　　war  类型

2.   pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
        http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>
    <groupId>com.java</groupId>
    <artifactId>upload</artifactId>
    <version>1.0.0</version>
    <packaging>war</packaging>

    <dependencies>

        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.4</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>

    </dependencies>

    <build>
        <finalName>${project.artifactId}</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>

        </plugins>
    </build>
</project>

3.   UploadFileServlet.java

package com.java.servlet;

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

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.FileUtils;

/**
 * 原生Servlet上传文件
 *
 */
public class UploadFileServlet extends HttpServlet {

    private static final long serialVersionUID = -755404037178760784L;

    /**
     * 设置字符集为UTF-8
     */
    private static final String ENCODING = "UTF-8";

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        if (ServletFileUpload.isMultipartContent(request)) {
            try {
                DiskFileItemFactory factory = new DiskFileItemFactory();
                ServletFileUpload upload = new ServletFileUpload(factory);
                List<FileItem> items = upload.parseRequest(request);

                // 存储普通表单参数
                Map<String, String> paramMap = new HashMap<>();

                // 存储文件参数
                Map<String, FileItem> fileMap = new HashMap<>();

                /* 解析表单参数 */
                for (FileItem item : items) {

                    // 普通表单参数
                    if (item.isFormField()) {
                        paramMap.put(item.getFieldName(), item.getString(ENCODING));
                    }

                    // 文件参数
                    else {
                        fileMap.put(item.getFieldName(), item);
                    }
                }

                /* 从参数集合中获取需要的参数 */
                String uploadPath = paramMap.get("uploadPath");
                FileItem fileItem = fileMap.get("file");
                String fileName = fileItem.getName();

                File outFile = new File(uploadPath, fileName);
                if (outFile.exists()) {
                    FileUtils.forceDelete(outFile);
                }
                fileItem.write(outFile);

                write(response, "上传完成:" + outFile.getAbsolutePath());
            } catch (FileUploadException e) {
                e.printStackTrace();
                write(response, e.getMessage());
            } catch (Exception e) {
                e.printStackTrace();
                write(response, e.getMessage());
            }
        }

        // 请求Content-type设置错误时给出提示
        else {
            write(response, "非multipart类型，检查Content-type");
        }

    }

    private void write(HttpServletResponse response, String message) {
        response.setContentType("text/html; charset=UTF-8");
        PrintWriter writer = null;
        try {
            writer = response.getWriter();
            writer.write(message);
            writer.flush();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            writer.close();
        }
    }

}

4.   web.xml

<?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"
    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>upload</display-name>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>

    <servlet>
        <servlet-name>uploadFile</servlet-name>
        <servlet-class>com.java.servlet.UploadFileServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>uploadFile</servlet-name>
        <url-pattern>/uploadFile</url-pattern>
    </servlet-mapping>
</web-app>

5.   新建页面文件  src/main/webapp/index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
%>

<!DOCTYPE html>
<html>

    <head>
        <title>上传文件</title>
        <base href="<%=basePath%>">
        <meta http-equiv="content-type" content="text/html; charset=UTF-8" />
    </head>

    <body>

        <form action="uploadFile" enctype="multipart/form-data" method="post">
            <table>
                <tr>
                    <th>选择上传文件:</th>
                    <td><input name="file" type="file" /></td>
                </tr>
                <tr>
                    <th>上传服务器路径:</th>
                    <td><input name="uploadPath" type="text" placeholder="上传服务器路径" /></td>
                </tr>
                <tr>
                    <td colspan="2"><button type="submit">上传</button></td>
                </tr>
            </table>
        </form>

    </body>

</html>

部署到tomcat下，启动

浏览器输入 http://localhost:8080/upload/

如下所示：

选择文件，输入上传路径  G:\Temp\Test  如下所示：

单击【上传】，返回信息如下：

上传完成:G:\Temp\Test\fastjson-1.2.49.jar

查看G:\Temp\Test，文件已上传成功！

.