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- 导入jar包commons-io-2.4.jar和commons-fileupload的jar包
- post请求
- form表单提交,要加属性标签:
enctype="multipart/form-data"
- servlet中,
boolean isMultipart = ServletFileUpload.isMultipartContent(request)
可以判断表单请求是否是文件上传. - 文件上传,简单案例:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>文件上传</title>
</head>
<body>
<!--form表单, 必须是post请求 , 必须添加enctype属性标签-->
<form action="upload" method="post" enctype="multipart/form-data">
<!--选择type=file-->
<input type="file" name="myfile" id="myfile"/>
<input type="submit" value="上传"/>
</form>
</body>
</html>
package com.credi.servlet;
import java.io.File;
import java.io.IOException;
import java.util.List;
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 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;
@WebServlet("/upload")
public class UploadServlet extends HttpServlet{
private static final long serialVersionUID = 1L;
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 1 . 得到服务器真实路径
String path = this.getServletConfig().getServletContext().getRealPath("/");
System.out.println(path);
// 2 . 创建工厂
DiskFileItemFactory factory = new DiskFileItemFactory();
// 3. 设置缓冲大小
factory.setSizeThreshold(1024*3);
// 4. 设置上传处理对象
ServletFileUpload upload = new ServletFileUpload(factory);
// 5. 设置上传限制
upload.setFileSizeMax(3*1024*1024); // 上传最大文件大小
upload.setHeaderEncoding("utf-8"); // 字符编码
// 6. 解析请求
try {
List<FileItem> items = upload.parseRequest(req);
// 校验非空
if(items != null){
//遍历items集合
for( FileItem fileItem : items){
//判断是否是普通表单 并且 是否上传了内容
if(!fileItem.isFormField()&&fileItem.getName()!=null&&!"".equals(fileItem.getName())){
//得到上传的文件名
String fileName = fileItem.getName();
//文件的上传服务器的路径
File uploader = new File(path + "/upload/");
//文件夹是否存在
if(!uploader.exists()){
//不存在就创建文件
uploader.mkdirs();
}
File file = new File(uploader,fileName);
//上传文件
fileItem.write(file);
}
}
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
- 文件下载:
- 1 . 超链接下载:
<!--超链接下载-->
<!--浏览器能识别的格式,例如图片,文本, 会在网页中显示-->
<a href="statics/images/a.jpe" target="_blank">图片</a>
<a href="statics/a.txt" target="_blank">文本</a>
<!--浏览器不能识别的格式,例如快捷方式,应用程序, 就会弹出框让用户下载-->
<a href="statics/qqmusic.lnk" target="_blank">快捷方式</a>
<a href="statics/qqmusic.exe"target="_blank">应用程序</a>
- 2 .第三方下载:
<!--随便一种方式去请求servlet-->
<a href="download?fileName=a.jpg">下载图片</a>
package com.credi.servlet;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/download")
public class DownLoadServlet extends HttpServlet{
private static final long serialVersionUID = 1L;
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//设置响应编码
resp.setCharacterEncoding("utf-8");
//随意各种方式 , 拿到下载图片的名称
String fileName =req.getParameter("fileName");
//图片在服务器的真实路径
String path = this.getServletConfig().getServletContext().getRealPath("/upload/"+fileName);
//下载弹出框的设置
resp.setHeader("content-disposition", "attachment;filename="+fileName);
//创建File对象
File file = new File(path);
//文件输入流
InputStream is = new FileInputStream(file);
//响应的输出流
ServletOutputStream os = resp.getOutputStream();
//定义字节数组
byte[] car = new byte[1024];
int len = 0;
//读进来
while(-1 != (len=is.read(car))){
//响应出去
os.write(car,0,len);
}
//关闭
os.flush();
os.close();
is.close();
}
}
- servlet3.0之后的文件上传
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>文件上传</title>
</head>
<body>
<!--form表单, 必须是post请求 , 必须添加enctype属性标签-->
<form action="upload" method="post" enctype="multipart/form-data">
<!--选择type=file , 请记住它的name值-->
<input type="file" name="myfile" id="myfile"/>
<input type="submit" value="上传"/>
</form>
</body>
</html>
package com.credi.servlet;
import java.io.File;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
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;
@WebServlet("/upload")
//1. 必须要加此注解
@MultipartConfig
public class UploadServlet extends HttpServlet{
private static final long serialVersionUID = 1L;
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 2 . 得到Part对象
Part part = req.getPart("myfile"); //type=file的input文件上传框标签的name值
// 3 . 得到上传文件的名称
String fileName = part.getSubmittedFileName();
// 4 . 文件上传服务器的真实路径
String path = this.getServletContext().getRealPath("/upload/");
// 判断文件夹是否存在 , 不存在则创建
File file = new File(path);
//文件夹是否存在
if(!file.exists()){
//不存在就创建文件
file.mkdirs();
}
// 5 . 上传文件 (服务器存放文件的路径+文件名)
part.write(path + fileName);
}
}
- 从数据库动态获取用户图片信息后 , 实现图片的动态加载
<img src="user?action=userHead&imageName=${user.head }">
//借助commons
private void userHead(HttpServletRequest request, HttpServletResponse response) throws IOException {
// 1、接收参数(图片名称)
String imageName = request.getParameter("imageName");
// 2、判断是否为空
if (StringUtil.isEmpty(imageName)) {
return;
}
// 3、得到文件存放在服务器的真实路径 request.getServletContext().getRealPath("/WEB-INF/upload/" + 头像名称);
String filePath = request.getServletContext().getRealPath("/WEB-INF/upload/" + imageName);
// 4、通过路径得到file对象
File file = new File(filePath);
// 5、判断file对象是否存在,并且是一个标准文件
if (!file.exists() || !file.isFile() ) {
return;
}
// 6、截取图片名称,得到图片后缀
String pic = imageName.substring(imageName.lastIndexOf(".") + 1, imageName.length());
// 判断是否为空
if (StringUtil.isEmpty(pic)) {
return;
}
// 7、根据不同的后缀,设置对象的响应MIME类型
if ("gif".equals(pic.toLowerCase())) {
response.setContentType("image/gif");
} else if ("png".equals(pic.toLowerCase())) {
response.setContentType("image/png");
} else if ("jpg".equals(pic.toLowerCase()) || "jpeg".equals(pic.toLowerCase())) {
response.setContentType("image/jpeg");
}
// 8、利用commons-io的jar包,拷贝file对象 FileUtils.copyFile(file,response.getOutputStream());
FileUtils.copyFile(file, response.getOutputStream());
}