文件上传分析
1.普通表单提交默认enctype="application/x-www-form-urlencoded";但是当表单中存在文件类型时,需要设置enctype="multipart/form-data",它不对字符进行编码,用于发送二进制的文件(即所有文件类型,如视频、图片、音乐、文档都可以用此类型entype);还有一种enctype="text/plain"用于发送纯文本内容。
2.表单请求方式必须为post。
3.接收时不能再用request.getParameter(),而是request.getInputStream()解析二进制流,得到ServletInputStream对象。
接下来我们来看看上传一个t文件接收到的二进制流转化为字符串是什么:
(1)表单提交页面:
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>练习</title>
</head>
<body>
<form action="/UploadServlet" enctype="multipart/form-data" method="post">
<input type="text" name="username">
<input type="password" name="pwd">
<input type="file" name="pic">
<input type="submit">
</form>
</body>
</html>
(2)接收文件流UploadServlet:
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
@WebServlet("/UploadServlet")
public class UploadServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取复杂表单的输入流
InputStream in=request.getInputStream();
//输入流转化为字符串
byte[] b=new byte[1024];
in.read(b);
System.out.println(new String(b));
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
}
运行项目:
(1)表单填写:
test.txt中的内容是:
hello world
好好学习,天天向上
(2)点击提交,运行结果:
------WebKitFormBoundaryzRSPAU9UKnMzdAUZ
Content-Disposition: form-data; name="username"
hello 灏忛奔
------WebKitFormBoundaryzRSPAU9UKnMzdAUZ
Content-Disposition: form-data; name="pwd"
12345
------WebKitFormBoundaryzRSPAU9UKnMzdAUZ
Content-Disposition: form-data; name="pic"; filename="test.txt"
Content-Type: text/plain
锘縣ello world
濂藉ソ瀛︿範锛屽ぉ澶╁悜涓?
------WebKitFormBoundaryzRSPAU9UKnMzdAUZ--
分析:------WebKitFormBoundaryzRSPAU9UKnMzdAUZ--是分隔符,用于分隔表单的每一个字段。运行结果中有中文乱码后续会处理。将二进制流转化为字符串除了上面用的read()方法,还可以用org.apache.commons.io.IOUtils.toString(in),不过要导入jar包。
FileUpload文件上传
FileUpload分析
fileUpload是apache的commons组件提供的上传组件,它最主要的工作就是帮我们解析request.getInpustream()。可以参考在线API文档:http://tool.oschina.net/apidocs/apidoc?api=commons-fileupload
使用fileUpload组件首先需要引入两个jar包:
- commons-fileUpload.jar
- commons-io.jar
fileUpload的核心类有DiskFileItemFactory、ServletFileUpload、FileItem。
使用fileUpload固定步骤:
- 创建工厂类:DiskFileItemFactory factory=new DiskFileItemFactory();
- 创建解析器:ServletFileUpload upload=new ServletFileUpload(factory);
- 使用解析器解析request对象:List<FileItem> list=upload.parseRequest(request);
一个FileItem对象对应一个表单项。FileItem类有如下方法:
- String getFieldName():获取表单项的name的属性值。
- String getName():获取文件字段的文件名。如果是普通字段,则返回null
- String getString():获取字段的内容。如果是普通字段,则是它的value值;如果是文件字段,则是文件内容。
- String getContentType():获取上传的文件类型,例如text/plain、image。如果是普通字段,则返回null。
- long getSize():获取字段内容的大小,单位是字节。
- boolean isFormField():判断是否是普通表单字段,若是,返回true,否则返回false。
表单提交页面同上,修改UploadServlet的代码如下:
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 sun.misc.IOUtils;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
@WebServlet("/UploadServlet")
public class UploadServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
DiskFileItemFactory factory=new DiskFileItemFactory();
ServletFileUpload upload=new ServletFileUpload(factory);
try {
List<FileItem> list=upload.parseRequest(request);
for (FileItem fileItem:list){
System.out.println("fieldName:"+fileItem.getFieldName());
System.out.println("name:"+fileItem.getName());
System.out.println("string:"+fileItem.getString());
System.out.println("contentType:"+fileItem.getContentType());
System.out.println("size:"+fileItem.getSize()+"byte");
System.out.println("isFieldForm:"+fileItem.isFormField());
System.out.println("*************");
}
} catch (FileUploadException e) {
e.printStackTrace();
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
}
运行结果:
(1)填写表单:
(2)test.txt同上,点击提交结果:
fieldName:username
name:null
string:mike
contentType:null
size:4byte
isFieldForm:true
*************
fieldName:pwd
name:null
string:12345
contentType:null
size:5byte
isFieldForm:true
*************
fieldName:pic
name:test.txt
string:???hello world
contentType:text/plain
size:18byte
isFieldForm:false
*************
FileUpload文件上传
表单提交页面不变,UploadServlet代码如下:
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 sun.misc.IOUtils;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.UUID;
@WebServlet("/UploadServlet")
public class UploadServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//文件名中文乱码处理,使第34行获得的fileName中文正常显示。
// 但是普通表单内容的中文乱码用getBytes("iso-8859-1","utf-8")处理
request.setCharacterEncoding("utf-8");
DiskFileItemFactory factory=new DiskFileItemFactory();
ServletFileUpload upload=new ServletFileUpload(factory);
//文件名中文乱码处理也可以如此写
// upload.setHeaderEncoding("utf-8");
//设置单个文件大小限制
upload.setFileSizeMax(1024*10);
//设置所有文件总和大小限制
upload.setSizeMax(1024*30);
try {
List<FileItem> list=upload.parseRequest(request);
System.out.println(list);
for (FileItem fileItem:list){
if (!fileItem.isFormField()){
String filName=fileItem.getName();
//利用UUID生成伪随机字符串,作为文件名避免重复
String uuid= UUID.randomUUID().toString();
//获取文件后缀名
String suffix=filName.substring(filName.lastIndexOf("."));
//获取文件上传目录路径,在项目部署路径下的upload目录里。若想让浏览器不能直接访问到图片,可以放在WEB-INF下
String uploadPath=request.getSession().getServletContext().getRealPath("/upload");
File file=new File(uploadPath);
file.mkdirs();
//写入文件到磁盘
fileItem.write(new File(uploadPath,uuid+suffix));
}
}
} catch (FileUploadException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
}