Apache commons validator provides a class to validate emails. Code: import org.apache.commons.validator.EmailValidator... Maven dependency: <dependency> <groupId>commons-validator</gr...

Parsing a CVS file seemed to be a sore spot for software development. It's not simple enough that you can roll your own code in a couple of hours, and yet not deemed big enough for a full-fledged project. As a result, there are multiple libraries, each one with its own quirks. This is a summary of some simple tests I've done with five CSV parsers. Apache commons CSV parser : Does not escape backslash. The backslash is treated as literal if not proceeding a double quote, but then there's no way to have a backslash as the last character before the ending quote (even though it's a rare scenario). IOException thrown for unmatched quotes SuperCSV parser Can't handle escapes inside quotes Throws Exception for...

Demo code for CSV parsing with Apache Commons CSV parser . Java code: import java.io.*; import org.apache.commons.csv... Test with a simple CSV file: psmith01,CLASS2B,Peter Smith 1,YEAR2,1,N,ADVANCED,... Result: Line 1 has 11 values: |psmith01| |CLASS2B|... The parser worked correctly. Test with a more complicated CSV file: "psmith01 abc", "CLASS2B " , " Peter... Result: Line 1 has 4 values: |psmith01 abc| |CLASS... The third line is invalid input, but throwing a Java IOException is a bit grave. Also, the parser is not able to escape a backslash. Add a new line in item two: "One", "Two ", "Three" Result: Line 2 has 3 values: |One| |Two | |...

Java reflection with Apache beanutils example. import org.apache.commons.beanutils.MethodUtils; ...

HTTP basic authentication is just Base64 encoded user name and password passed in as the Authorization header. So the following code works: // encode user name and password String credent... However, since JDK 1.2, there's a more Java friendly way: Authenticator.setDefault(new Authenticator() { ... Test code: import java.net.*; import java.io.*; pub...

This is the task: your client wants to know how the web application is used. That is pretty easy. A plethora of commercial tools or any of the free log analysis tools such as analog and AWStats would fit the bill. But here's the catch: they want to know not only what pages are visited by how many people and when, but also who logged in and did what. Your application is using form based authentication and therefore, everyone is anonymous in the web access log. What to do? This is a servlet filter that generates a web access log with authenticated user info that can be fed to log analysis tools such as analog and AWStats . Filter code (the output format is Apache...

I tried to find a GZIP compression servlet filter to compress a large log file that we send down to the browser. Most of the implementations I found were overly complicated and many buggy. This is a simple implementation that worked for me. The filter: package filter.demo; import java.io.*; i... Config web.xml : <filter> <filter-name>gzipFilter</filte... The ugly anonymous inner class could have been avoided if the servlet API did not insist on ServletResponse.getOutputStream returning the bogus ServletOutputStream class (instead of the plain OutputStream ). Additional Note: In an earlier version of this filter, the gzip headers were added in doFilter , like this: // This is NOT good! if (supportsGzip) { ... It turned out that the ServletResponse methods sendError bypasses the gzip...

Create the stuff you want to manufacture with the factory: package tc.demo; public class Junk { ... Create the factory: package tc.demo; import java.util.Enumerati... Tell Tomcat to use your factory. Create file context.xml and put it under the directory META-INF of your web application: <Context> <Resource name="/find/junk/here" ... Note that beside name , type and factory , you can put any arbitrary attribute in the Resource element. Access the thing with JNDI: <%@page language="java" import="javax.naming.*,tc.... The server side log looked like this: INFO: jndiName: here INFO: name: scope, value: ... Also note that, in contrast to Tomcat documentation , resource-ref is not needed in web.xml .

JavaDoc says that you can call getOutputStream or getWriter on ServletResponse , but you cannot call both. The second call will get IllegalStateException . So this works: import java.io.*; import javax.servlet.*; im... So does this: import java.io.*; import javax.servlet.*; im... But not this: import java.io.*; import javax.servlet.*; im... You can make the last servlet work if you insert a filter like this: import java.io.*; import javax.servlet.*; im... But depending on the underlying implementation, the order of the output strings may be undetermined.

This example decompresses a gzip compressed file with java.util.zip.GZIPInputStream . The input is assumed to be Base64 encoded after being gzipped (such would be the case when binary data is transmitted within an XML file). You don't need the Base64InputStream if the data is not Base64 encoded. import java.io.*; import java.util.zip.GZIPInpu...