springmvc的文件上传与下载

1、导入依赖包

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.3</version>
</dependency>
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>3.1.0</version>
</dependency>

2、web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

    <servlet>
        <servlet-name>dispatcherservlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springmvc-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcherservlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <!--配置过滤器-->
    <filter>
        <filter-name>encoding</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>encoding</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

</web-app>

3、springmvc-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/mvc
       https://www.springframework.org/schema/mvc/spring-mvc.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">

    <!--JSON乱码问题配置-->
<!--    <mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8"/>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>-->

    <!--自动扫描包,让指定包下的注解生效，由IOC容器统一管理-->
    <context:component-scan base-package="com.mzj.controller"/>

    <!--开启springmvc注解模式-->
    <mvc:annotation-driven/>

    <!--过滤静态资源-->
    <mvc:default-servlet-handler/>


    <!--视图解析器-->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
          id="internalResourceViewResolver">
        <!--前缀-->
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <!--后缀-->
        <property name="suffix" value=".jsp"/>
    </bean>

    <!--文件上传的配置-->
    <bean id="multipartResolver"
          class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!--请求编码格式，必须和jsp的pageEncoding属性一致，以便于正确读取表单数据，默认为ISO-8859-1 -->
        <property name="defaultEncoding" value="utf-8"/>
        <!-- 上传文件大小上限，单位为字节，10485760 = 10M -->
        <property name="maxUploadSize" value="10485760"/>
    </bean>
</beans>

4、创建上传页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<form action="${pageContext.request.contextPath}/upload" enctype="multipart/form-data" method="post">
    <input type="file" name="file" />
    <input type="submit" value="upload" />
</form>

5、在配置springmvc-servlet.xml文件中配置

<!--文件上传的配置-->
<bean id="multipartResolver"
      class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!--请求编码格式，必须和jsp的pageEncoding属性一致，以便于正确读取表单数据，默认为ISO-8859-1 -->
    <property name="defaultEncoding" value="utf-8"/>
    <!-- 上传文件大小上限，单位为字节，10485760 = 10M -->
    <property name="maxUploadSize" value="10485760"/>
</bean>

6、创建Controller

package com.mzj.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.commons.CommonsMultipartFile;

import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * @author XM
 */
@RestController
public class FileUpload {

    /**
     * 原生态文件上传写入，用字节输入输出流
     *
     * @param filename
     * @param file
     * @param request
     * @return
     * @throws IOException
     */
    @RequestMapping("/upload")
    public String fileupload(String filename, MultipartFile file, HttpServletRequest request) throws IOException {

        // 获取文件名
        String uploadFileName = file.getOriginalFilename();

        // 如果文件名为空，直接返回到首页
        if ("".equals(uploadFileName)) {
            return "redirect:/index.jsp";
        }
        System.out.println("上传文件名为：" + uploadFileName);

        // 上传路径保存设置
        String path = request.getServletContext().getRealPath("/upload");
        // 如果路径不存在就创建一个
        File realPath = new File(path);
        if (!realPath.exists()) {
            realPath.mkdir();
        }
        System.out.println("上传文件保存地址：" + realPath);

        // 文件输入流
        InputStream is = file.getInputStream();
        FileOutputStream os = new FileOutputStream(new File(realPath, uploadFileName));

        // 读取写出
        int len = 0;
        byte[] buffer = new byte[1024];
        while ((len = is.read(buffer)) != -1) {
            os.write(buffer, 0, len);
            os.flush();
        }
        os.close();
        is.close();
        return "redirect:/index.jsp";
    }

    /*
    采用file.transferTo来保存上传的文件
     */
    @RequestMapping("/uoload2")
    public String fileupload2(@RequestParam("file")CommonsMultipartFile file, HttpServletRequest request) throws IOException {
        // 上传路径保存设置
        String path = request.getServletContext().getRealPath("/upload");
        File realPath = new File(path);
        if (!realPath.exists()) {
            realPath.mkdir();
        }

        // 上传文件地址
        System.out.println("上传文件保存地址" + realPath);

        // 通过CommonsMultipartFile的方法直接写文件
        file.transferTo(new File(realPath + "/" + file.getOriginalFilename()));

        return "redirect:/index.jsp";
    }
}