SpringMVC-文件上传

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>springmvc</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>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <!--springmvc过滤器，防止乱码-->
    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>utf-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

</web-app>

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:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc
        https://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!--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.kakafa.controller"/>


    <!--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>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper">
                    <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                        <property name="failOnEmptyBeans" value="false"/>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>


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

    <!--springMVC的文件上传配置，这里的id必须为"multipartResolver"不然会出错-->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!--请求的编码格式，必须和JSP的pageEncoding属性一致，以便正确读取表单内容，默认为ISO-8859-1-->
        <property name="defaultEncoding" value="utf-8"/>
        <!--上传文件大小限制，单位为字节-->
        <property name="maxUploadSize" value="10485760"/>
        <property name="maxInMemorySize" value="40960"/>
    </bean>

</beans>

首页：


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>

<%--
  enctype="multipart/form-data"
  enctype就是encodetype就是编码类型的意思
  multipart/form-data是指表单数据有多部分构成，既有文本数据，又有文件等二进制数据的意思
--%>
  <form action="${pageContext.request.contextPath}/upload" enctype="multipart/form-data" method="post">
    <input type="file" name="file">
    <input type="submit" value="上传">
  </form>

  </body>
</html>

FileController

package com.kakafa.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.commons.CommonsMultipartFile;
import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;


@RestController
public class FileController {

    //方法一
    //@RequestParam("file")将jsp页面中name=file的控件得到的文件封装成CommonsMultipartFile对象
    //如果是多个文件批量上传，则CommonsMultipartFile为数组即可
    @RequestMapping("/upload")
    public String upload(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {

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

        //如果文件名为空则直接回到首页
        if (filename.equals("")){
            return "redirect:/index.jsp";
        }

        //上传路径保存设置
        //request.getServletContext().getRealPath("/sss")获得当前运行文件在服务器上的绝对路径
        String path = request.getServletContext().getRealPath("/sss");
        System.out.println("=======path:"+path);

        //如果路径不存在，创建一个
        File realPath=new File(path);
        if (!realPath.exists()){
            realPath.mkdir();//mkdir()是创建文件夹，createNewFile()是创建文件
        }
        System.out.println("=======上传文件保存地址：realPath"+realPath);

        InputStream is = file.getInputStream();
        FileOutputStream fos = new FileOutputStream(new File(realPath, filename));
        //读取写出
        int len=0;
        byte[] buffer=new byte[1024];
        while((len=is.read(buffer))!=-1){
            fos.write(buffer,0,len);
            fos.flush();//flush()方法将输入流和输出流中的缓冲进行刷新，使缓冲区中的元素及时做输入和输出，而不必等缓冲区满
        }
        fos.close();
        is.close();

        return "redirect:/index.jsp";
    }

    //方法二
    @RequestMapping("/upload2")
    public String  fileUpload2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {

        //上传路径保存设置
        String path = request.getServletContext().getRealPath("/sss");
        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（注意这个时候）
        file.transferTo(new File(realPath+"/"+ file.getOriginalFilename()));

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

测试结果：

注意：

1)request.getServletContext()方法报红问题

解决：getServletContext()方法是Servlet3.0添加的，所以需要引入3.0以上的jar包

2)报错：Error creating bean with name 'multipartResolver': Failed to introspect bean class

原因：没有commons-fileupload包导致的

解决：pom.xml导包,并且记得把包加入到lib中

        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.1</version>
        </dependency>