Admin: 1 версия

2010-06-01T05:06:53Z

1 версия

в 17:44, 31 мая 2010

2010-05-31T17:44:27Z

Новая страница

== Filter Response ==



<source lang="java">
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.security.*;
public class MyServlet implements Filter
{

private FilterConfig filterConfig = null;
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException
{
chain.doFilter(request, response);
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("The filter got this message: " + filterConfig.getInitParameter("message"));
}
public void destroy() { }
public void init(FilterConfig filterConfig) {
this.filterConfig = filterConfig;
}
}</source>



== Filter that uses a response wrapper to convert all output to uppercase ==



<source lang="java">
import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
public class UpperCaseFilter implements Filter {
protected FilterConfig config;
public void init(FilterConfig config) throws ServletException {
this.config = config;
}
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws ServletException, IOException {
ServletResponse newResponse = response;
if (request instanceof HttpServletRequest) {
newResponse = new CharResponseWrapper((HttpServletResponse) response);
}
chain.doFilter(request, newResponse);
if (newResponse instanceof CharResponseWrapper) {
String text = newResponse.toString();
if (text != null) {
text = text.toUpperCase();
response.getWriter().write(text);
}
}
}
}
class CharResponseWrapper extends HttpServletResponseWrapper {
protected CharArrayWriter charWriter;
protected PrintWriter writer;
protected boolean getOutputStreamCalled;
protected boolean getWriterCalled;
public CharResponseWrapper(HttpServletResponse response) {
super(response);
charWriter = new CharArrayWriter();
}
public ServletOutputStream getOutputStream() throws IOException {
if (getWriterCalled) {
throw new IllegalStateException("getWriter already called");
}
getOutputStreamCalled = true;
return super.getOutputStream();
}
public PrintWriter getWriter() throws IOException {
if (writer != null) {
return writer;
}
if (getOutputStreamCalled) {
throw new IllegalStateException("getOutputStream already called");
}
getWriterCalled = true;
writer = new PrintWriter(charWriter);
return writer;
}
public String toString() {
String s = null;
if (writer != null) {
s = charWriter.toString();
}
return s;
}
}
Simple response wrapper that utilizes a local CharArrayWriter for output

<filter>
<filter-name>Upper Case Filter</filter-name>
<filter-class>com.omh.filters.UpperCaseFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>Upper Case Filter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
*/</source>



== Servlet Filter Init Parameter ==



<source lang="java">
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.security.*;
public class MyServlet implements Filter
{

private FilterConfig filterConfig = null;
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException
{
System.out.println("The message is: " + filterConfig.getInitParameter("message"));
chain.doFilter(request, response);
}
public void destroy() { }
public void init(FilterConfig filterConfig) {
this.filterConfig = filterConfig;
}
}</source>



== Simple filter for measuring servlet response times ==



<source lang="java">
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
public class ResponseTimerFilter implements Filter {
protected FilterConfig config;
public void init(FilterConfig config) throws ServletException {
this.config = config;
}
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws ServletException, IOException {
long startTime = System.currentTimeMillis();
chain.doFilter(request, response);
long elapsed = System.currentTimeMillis() - startTime;
String name = "servlet";
if (request instanceof HttpServletRequest) {
name = ((HttpServletRequest) request).getRequestURI();
}
config.getServletContext().log(name + " took " + elapsed + " ms");
}
}
<filter>
<filter-name>Timing Filter</filter-name>
<filter-class>com.omh.filters.ResponseTimerFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>Timing Filter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
*/</source>



== Use Filter to Check Date ==



<source lang="java">
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.security.*;
public class MyServlet implements Filter
{
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException
{

GregorianCalendar calendar = new GregorianCalendar();
Date date1 = new Date();
calendar.setTime(date1);
int hour = calendar.get(Calendar.HOUR_OF_DAY);
if(hour < 9 || hour > 17) {
chain.doFilter(request, response);
} else {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<HTML>");
out.println("<HEAD>");
out.println("<TITLE>");
out.println("Get Back to Work!");
out.println("</TITLE>");
out.println("</HEAD>");
out.println("<BODY>");
out.println("<H1>Get Back to Work!</H1>");
out.println("Sorry, that resource is not available now.");
out.println("</BODY>");
out.println("</HTML>");
}
}
public void destroy()
{
}
public void init(FilterConfig filterConfig)
{
}
}</source>



== Use Filter to check Request Parameter ==



<source lang="java">
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.security.*;
public class MyServlet implements Filter
{
private FilterConfig filterConfig = null;
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException
{
String password = ((HttpServletRequest) request).getParameter("password");

if(password.equals("opensesame")) {
chain.doFilter(request, response);
} else {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<HTML>");
out.println("<HEAD>");
out.println("<TITLE>");
out.println("Incorrect Password");
out.println("</TITLE>");
out.println("</HEAD>");
out.println("<BODY>");
out.println("<H1>Incorrect Password</H1>");
out.println("Sorry, that password was incorrect.");
out.println("</BODY>");
out.println("</HTML>");
}
}
public void destroy() { }
public void init(FilterConfig filterConfig) {
this.filterConfig = filterConfig;
}
}</source>



== Use Filter to log Configuration ==



<source lang="java">
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.security.*;
public class MyServlet implements Filter
{
private FilterConfig filterConfig = null;
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException
{
long start = System.currentTimeMillis();
String address = request.getRemoteAddr();
String file = ((HttpServletRequest) request).getRequestURI();

chain.doFilter(request, response);
filterConfig.getServletContext().log(
"User access! " +
" User IP: " + address +
" Resource: " + file +
" Milliseconds used: " + (System.currentTimeMillis() - start)
);
}
public void destroy() { }
public void init(FilterConfig filterConfig) {
this.filterConfig = filterConfig;
}
}</source>



== Your First Filter ==



<source lang="java">
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.security.*;
public class MyServlet implements Filter
{
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException
{
System.out.println("In filter");
chain.doFilter(request, response);
System.out.println("Leaving filter");
}
public void destroy()
{
}
public void init(FilterConfig filterConfig)
{
}
}</source>

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Admin: 1 версия

в 17:44, 31 мая 2010