[slickquiz id=18]
Aug 16
ThreeParams.java Servlet that reads and displays three request (form) parameters. Uses the ServletUtilities class.
ThreeParams.java Servlet that reads and displays three request (form) parameters. Uses the ServletUtilities class.
package cwp;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
/** Simple servlet that reads three parameters from the
* form data.
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class ThreeParams extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Reading Three Request Parameters";
out.println(ServletUtilities.headWithTitle(title) +
"\n" +
"
" + title + "
\n" +
"
\n" +
"
param1: "
+ request.getParameter("param1") + "\n" +
"
param2: "
+ request.getParameter("param2") + "\n" +
"
param3: "
+ request.getParameter("param3") + "\n" +
"
\n" +
"");
}
}
Aug 16
ShowMessage.java Servlet that demonstrates the use of initialization parameters.
ShowMessage.java Servlet that demonstrates the use of initialization parameters. Remember that, to use this servlet, you have to do three things:
* Put the modified web.xml file in the WEB-INF directory.
* Restart the server.
* Use the registered servlet name (i.e., the URL http://host/servlet/ShowMsg), not the raw servlet name (i.e., the URL http://host/servlet/cwp.ShowMessage).
package cwp;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
/** Example using servlet initialization. Here, the message
* to print and the number of times the message should be
* repeated is taken from the init parameters.
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class ShowMessage extends HttpServlet {
private String message;
private String defaultMessage = "No message.";
private int repeats = 1;
public void init() throws ServletException {
ServletConfig config = getServletConfig();
message = config.getInitParameter("message");
if (message == null) {
message = defaultMessage;
}
try {
String repeatString = config.getInitParameter("repeats");
repeats = Integer.parseInt(repeatString);
} catch(NumberFormatException nfe) {
// NumberFormatException handles case where repeatString
// is null *and* case where it is in an illegal format.
}
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "The ShowMessage Servlet";
out.println(ServletUtilities.headWithTitle(title) +
"\n" +
"
" + title + "
");
for(int i=0; i" + message + "
");
}
out.println("");
}
}
web.xml
?
ShowMsg
cwp.ShowMessage
?
message
Shibboleth
?
repeats
5
Aug 15
ServletUtilities.java Utility class that simplifies the output of the DOCTYPE and HEAD in servlets, among other things. Used by most remaining servlets in the chapter.
ServletUtilities.java Utility class that simplifies the output of the DOCTYPE and HEAD in servlets, among other things. Used by most remaining servlets in the chapter.
package cwp;
import javax.servlet.*;
import javax.servlet.http.*;
/** Some simple time savers. Note that most are static methods.
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class ServletUtilities {
public static final String DOCTYPE =
"";
public static String headWithTitle(String title) {
return(DOCTYPE + "\n" +
"\n" +
"\n");
}
/** Read a parameter with the specified name, convert it
* to an int, and return it. Return the designated default
* value if the parameter doesn't exist or if it is an
* illegal integer format.
*/
public static int getIntParameter(HttpServletRequest request,
String paramName,
int defaultValue) {
String paramString = request.getParameter(paramName);
int paramValue;
try {
paramValue = Integer.parseInt(paramString);
} catch(NumberFormatException nfe) { // null or bad format
paramValue = defaultValue;
}
return(paramValue);
}
/** Given an array of Cookies, a name, and a default value,
* this method tries to find the value of the cookie with
* the given name. If there is no cookie matching the name
* in the array, then the default value is returned instead.
*/
public static String getCookieValue(Cookie[] cookies,
String cookieName,
String defaultValue) {
if (cookies != null) {
for(int i=0; i' with
* '>', and (to handle cases that occur inside attribute
* values), all occurrences of double quotes with
* '"' and all occurrences of '&' with '&'.
* Without such filtering, an arbitrary string
* could not safely be inserted in a Web page.
*/
public static String filter(String input) {
StringBuffer filtered = new StringBuffer(input.length());
char c;
for(int i=0; i') {
filtered.append(">");
} else if (c == '"') {
filtered.append(""");
} else if (c == '&') {
filtered.append("&");
} else {
filtered.append(c);
}
}
return(filtered.toString());
}
}
Aug 15
SimplerHelloWWW.java Servlet that uses ServletUtilities to simplify the generation of the DOCTYPE and HEAD part of the servlet.
SimplerHelloWWW.java Servlet that uses ServletUtilities to simplify the generation of the DOCTYPE and HEAD part of the servlet.
package cwp;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
/** Simple servlet that generates HTML. This variation of
* HelloWWW uses the ServletUtilities utility class
* to generate the DOCTYPE, HEAD, and TITLE.
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class SimplerHelloWWW extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println(ServletUtilities.headWithTitle("Hello WWW") +
"\n" +
"
Hello WWW
\n" +
"");
}
}
Servlet Utilities
package cwp;
import javax.servlet.*;
import javax.servlet.http.*;
/** Some simple time savers. Note that most are static methods.
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* May be freely used or adapted.
*/
public class ServletUtilities {
public static final String DOCTYPE =
"";
public static String headWithTitle(String title) {
return(DOCTYPE + "\n" +
"\n" +
"\n");
}
/** Read a parameter with the specified name, convert it
* to an int, and return it. Return the designated default
* value if the parameter doesn't exist or if it is an
* illegal integer format.
*/
public static int getIntParameter(HttpServletRequest request,
String paramName,
int defaultValue) {
String paramString = request.getParameter(paramName);
int paramValue;
try {
paramValue = Integer.parseInt(paramString);
} catch(NumberFormatException nfe) { // null or bad format
paramValue = defaultValue;
}
return(paramValue);
}
/** Given an array of Cookies, a name, and a default value,
* this method tries to find the value of the cookie with
* the given name. If there is no cookie matching the name
* in the array, then the default value is returned instead.
*/
public static String getCookieValue(Cookie[] cookies,
String cookieName,
String defaultValue) {
if (cookies != null) {
for(int i=0; i' with
* '>', and (to handle cases that occur inside attribute
* values), all occurrences of double quotes with
* '"' and all occurrences of '&' with '&'.
* Without such filtering, an arbitrary string
* could not safely be inserted in a Web page.
*/
public static String filter(String input) {
StringBuffer filtered = new StringBuffer(input.length());
char c;
for(int i=0; i') {
filtered.append(">");
} else if (c == '"') {
filtered.append(""");
} else if (c == '&') {
filtered.append("&");
} else {
filtered.append(c);
}
}
return(filtered.toString());
}
}
Aug 14
HelloWWW.java Servlet that generates HTML. This and all remaining servlets are in the cwp package and therefore should be installed in the cwp subdirectory.
HelloWWW.java Servlet that generates HTML. This and all remaining servlets are in the cwp package and therefore should be installed in the cwp subdirectory.
package cwp;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
/** Simple servlet that generates HTML.
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class HelloWWW extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String docType =
"\n";
out.println(docType +
"\n" +
"\n" +
"\n" +
"
Aug 14
HelloWorld.java Simple servlet that generates plain text.
HelloWorld.java Simple servlet that generates plain text.
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
/** Very simplistic servlet that generates plain text.
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class HelloWorld extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println("Hello World");
}
}
Aug 13
ServletTemplate.java Starting point for servlets.
ServletTemplate.java Starting point for servlets.
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
/** Servlet template.
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class ServletTemplate extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
// Use "request" to read incoming HTTP headers
// (e.g., cookies) and query data from HTML forms.
// Use "response" to specify the HTTP response status
// code and headers (e.g. the content type, cookies).
PrintWriter out = response.getWriter();
// Use "out" to send content to browser
}
}
Aug 13
StringBean.java Bean used to demonstrate jsp:useBean, etc. Remember to install it in the WEB-INF/classes/cwp directory.
StringBean.java Bean used to demonstrate jsp:useBean, etc. Remember to install it in the WEB-INF/classes/cwp directory.
package cwp;
/** A simple bean that has a single String property
* called message.
* <P>
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class StringBean {
private String message = "No message specified";
public String getMessage() {
return(message);
}
public void setMessage(String message) {
this.message = message;
}
}
