当使用 enctype="multipart/form-data" 属性时
根据Sending additional data with multipart，request.getParameter;不能使用 with enctype="multipart/form-data"。在 process.jsp，我没有使用request.getParameter. 但jsp:getProperty返回空值。删除enctype="multipart/form-data"工作正常。我想知道 enctype="multipart/form-data" 效果如何jsp:setProperty and jsp:getProperty。它们是如何连接的？我知道jsp:setProperty不是更喜欢的方式。当我使用旧代码时，没有使用框架或没有使用 MVC。但我必须使用 servlet 3.0 和 tomcat 8.5 运行。enctype="multipart/form-data"在使用Jsp 到 Jsp时，还有其他方法可以传递数据吗？
表单.jsp
<!-- <form action="process.jsp" method="post" enctype="application/x-www-form-urlencoded"> -->
<!-- <form action="process.jsp" method="post"> -->
<form action="process.jsp" method="post" enctype="multipart/form-data">
Name:<input type="text" name="name"><br>
Password:<input type="password" name="password"><br>
Email:<input type="text" name="email"><br>
File:<input type="file" name="fileName"><br>
<hr>
<input type="submit" value="register">
</form>
进程.jsp
<jsp:useBean id="bean" class="dao.User" scope="page">
<jsp:setProperty property="*" name="bean"/>
</jsp:useBean>
Record:<br>
<jsp:getProperty property="name" name="bean"/><br>
<jsp:getProperty property="password" name="bean"/><br>
<jsp:getProperty property="email" name="bean" /><br>
User.java
public class User {
private String name;
private String password;
private String email;
private String fileName;
// getter and setter...
}
慕码人8056858浏览 175回答 2
2回答
-
慕娘9325324
您可以使用 jsp 将文件上传到带有其他输入字段的服务器。前任。索引.jsp<form action="upload.jsp" method="post" enctype="multipart/form-data"><input type="file" name="file" size="50" /><br><input type="text" name="name" /><br /><input type="submit" value="Upload File" /></form>上传.jsp<%@ page import="java.io.*,java.util.*, javax.servlet.*"%><%@ page import="javax.servlet.http.*"%><%@ page import="org.apache.commons.fileupload.*"%><%@ page import="org.apache.commons.fileupload.disk.*"%><%@ page import="org.apache.commons.fileupload.servlet.*"%><%@ page import="org.apache.commons.io.output.*"%><html><head></head><body> <% File file; int maxFileSize = 5000 * 1024; int maxMemSize = 5000 * 1024; String filePath = "D:/"; String contentType = request.getContentType(); if ((contentType.indexOf("multipart/form-data") >= 0)) { DiskFileItemFactory factory = new DiskFileItemFactory(); factory.setSizeThreshold(maxMemSize); factory.setRepository(new File("c:\\temp")); ServletFileUpload upload = new ServletFileUpload(factory); upload.setSizeMax(maxFileSize); try { List fileItems = upload.parseRequest(request); Iterator i = fileItems.iterator(); out.println("<html>"); out.println("<body>"); while (i.hasNext()) { FileItem fi = (FileItem) i.next(); if (!fi.isFormField()) { String fieldName = fi.getFieldName(); String fileName = fi.getName(); boolean isInMemory = fi.isInMemory(); long sizeInBytes = fi.getSize(); file = new File(filePath + fileName); //fi.write(file); out.println("Uploaded Filename: " + filePath + fileName + "<br>"); }else{ System.out.println(fi.getFieldName() +":"+fi.getString()); } } out.println("</body>"); out.println("</html>"); } catch (Exception ex) { System.out.println(ex); } } else { out.println("<html>"); out.println("<body>"); out.println("<p>No file uploaded</p>"); out.println("</body>"); out.println("</html>"); } %></body></html>您需要在 servlet jar 中包含 jar 文件 commons-fileupload。 -
慕雪6442864
我发现为什么enctype="multipart/form-data"不使用jsp:setProperty and jsp:getProperty. 当我使用 tomcat 运行时，process.jsp 生成为 process_jsp.java。 dao.User bean = null; bean = (dao.User) _jspx_page_context.getAttribute("bean", javax.servlet.jsp.PageContext.PAGE_SCOPE); if (bean == null){ bean = new dao.User(); _jspx_page_context.setAttribute("bean", bean, javax.servlet.jsp.PageContext.PAGE_SCOPE); out.write('\n'); org.apache.jasper.runtime.JspRuntimeLibrary.introspect(_jspx_page_context.findAttribute("bean"), request); out.write(' '); out.write(' '); out.write('\n'); }根据上面的源代码org.apache.jasper.runtime.JspRuntimeLibrary.introspect被调用。 public static void introspect(Object bean, ServletRequest request) throws JasperException { Enumeration<String> e = request.getParameterNames(); while ( e.hasMoreElements() ) { String name = e.nextElement(); String value = request.getParameter(name); introspecthelper(bean, name, value, request, name, true); } }上面的代码映射请求参数和名称（bean 属性名称），然后introspecthelper将通过使用将值传递给适当的 setter 方法java.lang.reflect.Method.invoke。与 一起工作时enctype="multipart/form-data"，Enumeration<String> e = request.getParameterNames()是问题所在。没有找到元素，所以introspecthelper永远不会执行。因为JspRuntimeLibrary.introspect是静态方法。我不能覆盖它的行为。那么，编写自定义标签或遵循如何使用 JSP/Servlet 将文件上传到服务器？是解决问题的唯一方法。
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