在学习Servlet过程中,针对图片上传做了一个Demo,实现的功能是:在a页面上传图片,点击提交后,将图片保存到服务器指定路径(D:/image);跳转到b页面,b页面读取展示绝对路径(D:/image)的图片。主要步骤如下:
步骤一:上传页面uploadphoto.jsp
需要注意两个问题:
1.form 的method必须是post的,get不能上传文件, 还需要加上enctype="multipart/form-data" 表示提交的数据是二进制文件。
2.需要提供type="file" 的字段进行上传
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<%@ page language= "java" contentType= "text/html; charset=UTF-8" pageEncoding= "UTF-8" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" " http://www.w3.org/TR/html4/loose.dtd " > <html> <head> <meta http-equiv= "Content-Type" content= "text/html; charset=UTF-8" > <title>upload page</title> </head> <body > <form action= "uploadPhoto" method= "post" enctype= "multipart/form-data" > 英雄名称: <input type= "text" name= "heroName" /> <br><br> 上传头像: <input type= "file" name= "filepath" /> <br><br> <input type= "submit" value= "上传" > </form> </body> </html> |
步骤二:UploadPhotoServlet类
1. 需要用到两个第三方的jar包,commons-io-1.4.jar和commons-fileupload-1.2.2.jar。项目是Maven项目,直接在pom.xml文件中引入:
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<dependency> <groupId>commons-io</groupId> <artifactId>commons-io</artifactId> <version> 2.4 </version> </dependency> <dependency> <groupId>commons-fileupload</groupId> <artifactId>commons-fileupload</artifactId> <version> 1.3 . 1 </version> </dependency> |
2. 前部分代码是固定写法,用来做一些准备工作。 直到遍历出Item,一个Item就是对应一个浏览器提交的数据,通过item.getInputStream可以打开浏览器上传的文件的输入流。
3. 客户提交的文件名有可能是一样的,所以在服务端保存文件的时候,不能使用客户提交的文件名。这里使用的是一种粗糙的解决文件名重复的办法,即使用时间戳。
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package servlet; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Iterator; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; 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; public class UploadPhotoServlet extends HttpServlet { public static String filename = null ; /** * */ private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request,HttpServletResponse response){ } @SuppressWarnings ( "rawtypes" ) public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException{ DiskFileItemFactory factory = new DiskFileItemFactory(); ServletFileUpload upload = new ServletFileUpload(factory); factory.setSizeThreshold( 1024 * 1024 ); List items = null ; try { items = upload.parseRequest(request); } catch (FileUploadException e) { e.printStackTrace(); } Iterator iter = items.iterator(); while (iter.hasNext()){ FileItem item = (FileItem) iter.next(); if (!item.isFormField()){ // 根据时间戳创建头像文件 filename = System.currentTimeMillis() + ".jpg" ; System.out.println(request.getContextPath()); /*File f = new File(getServletContext().getRealPath("upload"));*/ File f = new File( " D://image " ); if (!f.exists()) { f.mkdir(); } String imgsrc = f + "/" + filename; // 复制文件 InputStream is = item.getInputStream(); FileOutputStream fos = new FileOutputStream(imgsrc); byte b[] = new byte [ 1024 * 1024 ]; int length = 0 ; while (- 1 != (length = is.read(b))) { fos.write(b, 0 , length); } fos.flush(); fos.close(); } else { System.out.println(item.getFieldName()); String value = item.getString(); value = new String(value.getBytes( "ISO-8859-1" ), "UTF-8" ); System.out.println(value); } } //request.setAttribute("filename", filename); //request.getRequestDispatcher("/showPhoto").forward(request, response); response.sendRedirect( "/ServletTest/showPhoto?filename=" +filename); } } |
步骤三:ShowPhotoServlet类
其实这个类可以省略,即可以直接在UploadPhotoServlet类中跳转到页面showphoto.jsp,但是为了学习Servlet跳转方面的知识,于是增加一个新的Servlet类。
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package servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ShowPhotoServlet extends HttpServlet{ /** * */ private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException{ String filename = request.getParameter( "filename" ).toString(); response.sendRedirect( "/ServletTest/showphoto.jsp?filename=" +filename); } public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException{ String filename = request.getAttribute( "filename" ).toString(); request.setAttribute( "filename" , filename); request.getRequestDispatcher( "/showphoto.jsp" ).forward(request, response); } } |
1.servlet跳转至jsp(注意)
详见:http://www.zzvips.com/article/120301.htm
a.服务端跳转浏览器的地址不变(请求转发)
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request.setAttribute( "filename" , filename); request.getRequestDispatcher( "/showphoto.jsp" ).forward(request, response); |
b.客户端跳转浏览器的地址发生变化(请求重定向)
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response.sendRedirect( "/ServletTest/showphoto.jsp?filename=" +filename); |
2.servlet跳转至另一个servlet
a.服务端跳转需要重写doPost以获取传递参数
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String filename = request.getAttribute( "filename" ).toString(); |
b.客户端跳转需要重写doGet以获取传递参数
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String filename = request.getParameter( "filename" ).toString(); |
步骤三:web.xml配置
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<servlet> <servlet-name>UploadPhotoServlet</servlet-name> <servlet- class >servlet.UploadPhotoServlet</servlet- class > </servlet> <servlet-mapping> <servlet-name>UploadPhotoServlet</servlet-name> <url-pattern>/uploadPhoto</url-pattern> </servlet-mapping> <servlet> <servlet-name>ShowPhotoServlet</servlet-name> <servlet- class >servlet.ShowPhotoServlet</servlet- class > </servlet> <servlet-mapping> <servlet-name>ShowPhotoServlet</servlet-name> <url-pattern>/showPhoto</url-pattern> </servlet-mapping> |
步骤四:展示页面showphoto.jsp
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<%@ page language= "java" contentType= "text/html; charset=UTF-8" pageEncoding= "UTF-8" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" " http://www.w3.org/TR/html4/loose.dtd " > <html> <head> <meta http-equiv= "Content-Type" content= "text/html; charset=UTF-8" > <title>Image page</title> </head> <body> <% String filename = request.getParameter( "filename" ); String srcimg = "/image/" +filename; %> <img src= "<%=srcimg%>" /> </body> </html> |
1.配置虚拟路径
图片和工程不在一个盘符下。图片也不能放到工程下。 在JSP 文件中 <img src="C:/Users/fx/Pictures/test.jpg"/> 这样是引不到图片的。因为,JSP页面在引图片的时候是在页面解析的路径是:<img src="http://localhost:8080/test/images/1.jpg">。也就是说JSP在引图片的时候是先去工程目录下找的。
解决办法:
使用虚拟路径来配置,在tomcat下的server.xml中增加一个代码 在<Host></Host>中间:
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<Context docBase= "D:\image" path= "/image" reloadable= "true" /> |
然后在JSP页面中<img src = "/image/(图片名)">就可以访问图片了。
最终实现效果:
上传界面:
展示界面:
保存图片的文件夹:
总结
以上所述是小编给大家介绍的通过Java Servlet图片上传至指定文件夹并显示图片,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持!
原文链接:http://www.cnblogs.com/Junsept/p/7279343.html