借鑑博客:https://www.cnblogs.com/hellokuangshen/p/11289940.html
文件上傳和下載
springMVC 可以很好的支持文件上傳,但是SpringMVC上下文中默認沒有裝配MultipartResolver,因此默認情況下其不能處理文件上傳工作。如果想使用Spring的文件上傳功能,則需要在上下文中配置MultipartResolver。
準備工作
前端表單要求:爲了能上傳文件,必須將表單的method設置爲POST,並將enctype設置爲multipart/form-data。只有在這樣的情況下,瀏覽器纔會把用戶選擇的文件以二進制數據發送給服務器;
對錶單中的 enctype 屬性做個詳細的說明:
- application/x-www=form-urlencoded:默認方式,只處理表單域中的 value 屬性值,採用這種編碼方式的表單會將表單域中的值處理成 URL 編碼方式。
- multipart/form-data:這種編碼方式會以二進制流的方式來處理表單數據,這種編碼方式會把文件域指定文件的內容也封裝到請求參數中,不會對字符編碼。
- text/plain:除了把空格轉換爲 “+” 號外,其他字符都不做編碼處理,這種方式適用直接通過表單發送郵件。
<form action="" enctype="multipart/form-data" method="post">
<input type="file" name="file"/>
<input type="submit">
</form>
一旦設置了enctype爲multipart/form-data,瀏覽器即會採用二進制流的方式來處理表單數據,而對於文件上傳的處理則涉及在服務器端解析原始的HTTP響應。
Spring MVC爲文件上傳提供了直接的支持,這種支持是用即插即用的MultipartResolver實現的。Spring MVC使用Apache Commons FileUpload技術實現了一個MultipartResolver實現類:CommonsMultipartResolver。因此,SpringMVC的文件上傳還需要依賴Apache Commons FileUpload的組件。
在springmvc-servlet.xml進行配置文件如下:
注意!!!這個bena的id必須爲:multipartResolver , 否則上傳文件會報400的錯誤!在這裏栽過坑,教訓!
<!--文件上傳配置-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<!-- 請求的編碼格式,必須和jSP的pageEncoding屬性一致,以便正確讀取表單的內容,默認爲ISO-8859-1 -->
<property name="defaultEncoding" value="utf-8"/>
<!-- 上傳文件大小上限,單位爲字節(10485760=10M) -->
<property name="maxUploadSize" value="10485760"/>
<property name="maxInMemorySize" value="40960"/>
</bean>
除此之外,我們還需要導入文件上傳的jar包,commons-fileupload , Maven會自動幫我們導入他的依賴包 commons-io包;
<!--文件上傳-->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.3</version>
</dependency>
我們會使用它的實現類 CommonsMultipartFile , 常用方法
String getOriginalFilename():獲取上傳文件的原名
InputStream getInputStream():獲取文件流
void transferTo(File dest):將上傳文件保存到一個目錄文件中
我們去實際測試一下
springMVC實現文件上傳
方式一:採用流的方式上傳文件
controller文件:
//文件上傳:流
@RequestMapping("/upload")
@ResponseBody
public String upload(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
//1.獲得文件名
String filename = file.getOriginalFilename();
if ("".equals(filename)){
return "文件不存在";
}
//2.上傳文件保存路徑
String path = request.getServletContext().getRealPath("/upload");
File realPath = new File(path);
if (!realPath.exists()){
realPath.mkdir();
}
//3.上傳文件
InputStream is = file.getInputStream();
FileOutputStream os = new FileOutputStream(new File(realPath, filename));
int len = 0;
byte[] buffer = new byte[1024];
while ((len=is.read(buffer))!=-1){
os.write(buffer,0,len);
os.flush();
}
//4.關閉流
os.close();
is.close();
return "上傳完畢";
}
前端頁面:
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<body>
<form enctype="multipart/form-data" method="post" action="${pageContext.request.contextPath}/upload2">
<input type="file" name="file">
<<input type="submit">
</form>
</body>
</html>
結果輸出:
採用file.Transto 來上傳
controller:
文件上傳:CommonsMultipartFile
@RequestMapping(value = "/upload2")
@ResponseBody
public String upload2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
//上傳文件保存路徑
String path = request.getServletContext().getRealPath("/upload");
File realPath = new File(path);
if (!realPath.exists()){
realPath.mkdir();
}
//transferTo:將文件寫入到磁盤,參數就是一個文件
file.transferTo(new File(realPath+"/"+file.getOriginalFilename()));
return "上傳完畢";
}
其他文件配置不變
完整項目實現
項目結構:
pom.xml文件配置:
<?xml version="1.0" encoding="UTF-8"?>
<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">
<parent>
<artifactId>SpringMVC</artifactId>
<groupId>com.kuang</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>demo07_springmvc_file_intercepter</artifactId>
<packaging>war</packaging>
<name>demo07_springmvc_file_intercepter Maven Webapp</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<!--文件上傳和下載的包commons-fileupload,依賴於commons-io-->
<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.3</version>
</dependency>
</dependencies>
<build>
<finalName>demo07_springmvc_file_intercepter</finalName>
<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
<plugins>
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
</plugin>
<plugin>
<artifactId>maven-war-plugin</artifactId>
<version>3.2.2</version>
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
web.xml文件配置:
<?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_3_0.xsd"
id="WebApp_ID" version="3.0">
<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>
<!--配置過濾器-->
<filter>
<filter-name>myFilter</filter-name>
<!--<filter-class>com.kuang.filter.GenericEncodingFilter</filter-class>-->
<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>
<!--/* 包括.jsp-->
<filter-mapping>
<filter-name>myFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
springmvc-servlet.xml文件配置:
<?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_3_0.xsd"
id="WebApp_ID" version="3.0">
<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>
<!--配置過濾器-->
<filter>
<filter-name>myFilter</filter-name>
<!--<filter-class>com.kuang.filter.GenericEncodingFilter</filter-class>-->
<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>
<!--/* 包括.jsp-->
<filter-mapping>
<filter-name>myFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
fileUploadController文件:
package com.kuang.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
import sun.security.util.Length;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URL;
import java.net.URLEncoder;
@Controller
public class FileUploadController {
//文件上傳:流
@RequestMapping("/upload")
@ResponseBody
public String upload(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
//1.獲得文件名
String filename = file.getOriginalFilename();
if ("".equals(filename)){
return "文件不存在";
}
//2.上傳文件保存路徑
String path = request.getServletContext().getRealPath("/upload");
File realPath = new File(path);
if (!realPath.exists()){
realPath.mkdir();
}
//3.上傳文件
InputStream is = file.getInputStream();
FileOutputStream os = new FileOutputStream(new File(realPath, filename));
int len = 0;
byte[] buffer = new byte[1024];
while ((len=is.read(buffer))!=-1){
os.write(buffer,0,len);
os.flush();
}
//4.關閉流
os.close();
is.close();
return "上傳完畢";
}
//文件上傳:CommonsMultipartFile
@RequestMapping(value = "/upload2")
@ResponseBody
public String upload2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
//上傳文件保存路徑
String path = request.getServletContext().getRealPath("/upload");
File realPath = new File(path);
if (!realPath.exists()){
realPath.mkdir();
}
//transferTo:將文件寫入到磁盤,參數就是一個文件
file.transferTo(new File(realPath+"/"+file.getOriginalFilename()));
return "上傳完畢";
}
}
文件下載實現
文件下載步驟:
設置 response 響應頭
讀取文件 – InputStream
寫出文件 – OutputStream
執行操作
關閉流 (先開後關)
代碼實現:
@RequestMapping(value="/download")
public String downloads(HttpServletResponse response) throws Exception{
//要下載的圖片地址
String path = "C:/Users/Administrator/Desktop/";
String fileName = "1.png";
//1、設置response 響應頭
response.reset(); //設置頁面不緩存,清空buffer
response.setCharacterEncoding("UTF-8"); //字符編碼
response.setContentType("multipart/form-data"); //二進制傳輸數據
//設置響應頭
response.setHeader("Content-Disposition",
"attachment;fileName="+URLEncoder.encode(fileName, "UTF-8"));
File file = new File(path,fileName);
//2、 讀取文件--輸入流
InputStream input=new FileInputStream(file);
//3、 寫出文件--輸出流
OutputStream out = response.getOutputStream();
byte[] buff =new byte[1024];
int index=0;
//4、執行 寫出操作
while((index= input.read(buff))!= -1){
out.write(buff, 0, index);
out.flush();
}
out.close();
input.close();
return null;
}