1 servlet/jsp miscellaneous representation and management of data on the web
Post on 20-Dec-2015
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Servlet/JSP MiscellaneousServlet/JSP Miscellaneous
Representation and Management of
Data on the Web
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Uploading Files with Uploading Files with ServletsServlets
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Handling Uploads with Package Handling Uploads with Package Commons FileUploadCommons FileUpload
• Commons FileUpload is a package of Apache for
handling uploaded files in the Servlet side
• Files are sent in the body of post requests
• Using this package, uploaded files are
temporarily written into the memory or the disk
(depending on the file size)
• You can set the size threshold beyond which
files are written to disk
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Handling Uploads with Package Handling Uploads with Package Commons FileUploadCommons FileUpload
• Servlets read the file from the disk or memory
• In Tomcat, the default temporary directory is $CATALINA_BASE/temp/
• However, you can specify a temporary directory
of your own (e.g., /tmp)
• What if a very big file is uploaded?- You can define the maximal size of uploaded files
- Exception is thrown for larger files
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Example 1Example 1
<html> <head> <title>Upload Files and Parameters</title> </head> <body> <form action="upload1" method="post" enctype="multipart/form-data">
<h2>File:<input type="file" name="file1"/></h2><h2><input type="submit" value="send" /></h2> </form> </body></html>
upload1.htmlupload1.html
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public class Upload1 extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
DiskFileUpload upload = new DiskFileUpload(); upload.setSizeThreshold(1000); upload.setSizeMax(60000); try { List items = upload.parseRequest(request); Iterator it = items.iterator(); FileItem item = (FileItem) it.next(); response.setContentType(item.getContentType()); response.setContentLength((int)item.getSize());
Upload1.javaUpload1.java
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InputStream is = item.getInputStream(); OutputStream os = response.getOutputStream(); byte[] buffer = new byte[4096]; int read = -1; while((read=is.read(buffer))>=0) os.write(buffer,0,read); } catch (FileUploadException exp) { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<html><body><b>Error</b>: <i>" + exp.getMessage() + "</i></body></html>"); } }} Upload1.javaUpload1.java
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Example 2Example 2
<html> <head> <title>Upload Files and Parameters</title> </head> <body> <form action="upload2" method="post" enctype="multipart/form-data"> <h2>Parameter x: <input type="text" name="x" /></h2> <h2>File: <input type="file" name="file1" /></h2> <h2>Parameter y: <input type="text" name="y" /></h2> <h2><input type="submit" value="send" /></h2> </form> </body></html>
upload2.htmlupload2.html
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List items = upload.parseRequest(request); Iterator it = items.iterator(); out.println("<ol>"); while (it.hasNext()) { FileItem item = (FileItem) it.next(); if (item.isFormField()) out.println("<li><b>Field</b>: " + item.getFieldName() + " = " + item.getString() + "</li>"); else out.println("<li><b>File</b>" + ": parameter name: " + item.getFieldName() + ", file name: " + item.getName() + ", file size: " + item.getSize() + " bytes, file type: " + item.getContentType() + "</li>"); } out.println("</ol>"); Upload2.javaUpload2.java
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Example 3Example 3
• The latter example reflected a common design problem:
combining complex HTML code and Java code in a
Servlet or a JSP- Java code for processing parameters and uploaded files
- HTML code for generating the (dynamic) response
• An accepted solution is to process the parameters in a
Servlet, and forward the request to a JSP for generating
the response- Attributes can be sent to the JSP
• The next example also uses JSTL
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JSTLJSTL
• JSTL stands for JSP Standard Tag Library
• This is a regular tag library that can be imported
to your page, like the ones we created in the past
• This library includes some standard actions that
are common in JSP, like iteration and conditions
over EL expressions, parsing/manipulation of
XML and database access
• More details can be found in Sun's J2EE Tut.
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Example 3Example 3
<html> <head> <title>Upload Files and Parameters</title> </head> <body> <form action="upload3" method="post" enctype="multipart/form-data"> <h2>Parameter x: <input type="text" name="x" /></h2> <h2>File: <input type="file" name="file1" /></h2> <h2>Parameter y: <input type="text" name="y" /></h2> <h2><input type="submit" value="send" /></h2> </form> </body></html>
upload3.htmlupload3.html
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List formParams = new LinkedList();List files = new LinkedList();
List items = upload.parseRequest(request);Iterator it = items.iterator();
while (it.hasNext()) { FileItem item = (FileItem) it.next(); if (item.isFormField())formParams.add(item); else files.add(item); }
request.setAttribute("formParams",formParams);request.setAttribute("files",files);
this.getServletContext().getRequestDispatcher ("/WEB-INF/jsp/upload3.jsp").forward(request,response);
Upload3.javaUpload3.java
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<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %><%@ page isELIgnored="false" %><html><head><title>Submitted Parameters</title></head> <body><h1>Submitted Parameters:</h1><ol>
<c:forEach var="item" items="${formParams}"> <li><b>Parameter</b>: name:<i>${item.fieldName}</i>, value:<i>${item.string}</i></li> </c:forEach> <c:forEach var="item" items="${files}"> <li><b>File</b>: name:<i>${item.name}</i>, length:<i>${item.size}</i>, size:<i>type:${item.contentType}</i></li> </c:forEach> </ol></body></html> /WEB-INF/jsp/upload3.jsp/WEB-INF/jsp/upload3.jsp
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A QuestionA Question
What is the advantage of redirecting to JSP pages
that are under WEB-INF?
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Managing User Managing User Authentication with Authentication with
TomcatTomcat
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A ReminderA Reminder
create table users (
username varchar(30) not null primary key,
pass varchar(30) not null
);
create table users_roles (
username varchar(30) not null,
role varchar(30) not null,
primary key (username,role),
foreign key (username) references users(username)
);
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In server.xmlIn server.xml<Realm
className="org.apache.catalina.realm.JDBCRealm"
driverName="oracle.jdbc.driver.OracleDriver"
connectionURL="jdbc:oracle:thin:snoopy/snoopy@sol4:1521:stud"
userTable="users"
userNameCol="username"
userCredCol="pass"
userRoleTable="users_roles"
roleNameCol="role"/>
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User TablesUser Tables
• What if we do not have one table that stores
usernames and passwords? What if we only have
one role for the all users?
• What if we wanted the above information to be
stored in several tables (e.g., users and
administrators)
• The idea is to use views rather than real tables
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Creating ViewsCreating Views
create view up as
(select username u, pass p from users
union
select u,p from admin);
create view ur as
(select username u, 'myRole' r from users
union
select u, 'admin' r from admin);
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Fixing server.xmlFixing server.xml<Realm
className="org.apache.catalina.realm.JDBCRealm"
driverName="oracle.jdbc.driver.OracleDriver"
connectionURL="jdbc:oracle:thin:snoopy/snoopy@sol4:1521:stud"
userTable="up"
userNameCol="u"
userCredCol="p"
userRoleTable="ur"
roleNameCol="r"/>