Implementing Tomcat Custom Valve - tomcat6

Question

I am trying to implement a custom valve in Tomcat, say MyValve which extends BaseValve.
I created a jar of the project and added it into the Tomcat\lib folder.
The next step is of configuring the server.xml or context.xml.
I tried both.
But my valve class is not getting detected.
Could someone please let me know the steps to create a valve and use it.
Thanks

Answer 1

The question is on steps required to create a custom valve and use it. So let me explain it step by step for someone else also to take advantage of it. For my example, I will use a Java Maven Project. (Git Project)
Step 1: Open a new or existing maven project (you can also clone from the above repo).
Step 2: Add the following dependency to the pom.xml file.
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-catalina</artifactId>
<version>7.0.85</version>
<scope>provided</scope>
</dependency>
Step 3: Under src/main/java path, create a package and create a new Java Class: TomcatValve.java (could be any name). Extend this class by ValueBase class.
Step 4: With this, you will have to implement its invoke method. The entire class would look something similar to this:
import java.io.IOException;
import java.util.Enumeration;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.catalina.valves.ValveBase;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
/**
* #author Keet Sugathadasa
*/
public class TomcatValve extends ValveBase {
private static final Logger logger = Logger.getLogger(TomcatValve.class.getName());
public void invoke(Request request, Response response) throws IOException, ServletException {
HttpServletRequest httpServletRequest = request.getRequest();
Enumeration<String> headerNames = httpServletRequest.getHeaderNames();
logger.info("Receiving request");
while (headerNames.hasMoreElements()) {
String header = headerNames.nextElement();
logger.log(Level.INFO, "Header --> {0} Value --> {1}", new Object[]{header, httpServletRequest.getHeader(header)});
}
getNext().invoke(request, response);
}
}
Step 5: Open a terminal, and run mvn install. Now in the target/ folder, there jar should have been built.
Step 6: Copy this jar to ${TOMCAT_HOME}/lib or ${CATALINA_HOME}/lib folder. This is usually in /usr/local/apache-tomcat9/lib.
Step 7: Go to ${TOMCAT_HOME}/conf or ${CATALINA_HOME}/conf folder and add the following line to server.xml:
Classname: TomcatValve
PackageName: com.keetmalin.tomcat
<Valve className="com.keetmalin.tomcat.TomcatValve"/>
Step 9: Go to ${TOMCAT_HOME}/bin or ${CATALINA_HOME}/bin folder and run the following command in a terminal:
./catalina.sh run
Step 10: Next, your Tomcat server will start. Open a browser and go to http://localhost:8080/ and go back to the terminal. You will see that the logs are being printed. Now instead of printing logs, you can do anything you wish. Hope it helps!

Answer 2

What version of Tomcat are you running? The CATALINA_HOME\lib is the correct directory for Tomcat v6.x (and v7, I believe). If your valve is not getting picked up it could be that you are not editing the server.xml or context.xml files in your CATALINA_BASE directory. Are you using Eclipse IDE or something similar? If so, check your Tomcat server settings because it copies XML files from CATALINA_HOME (installation) to CATALINA_BASE (configured instance) directory. This problem tripped me up for a while.

Answer 3

I found that I had created a jar which contained the java file, instead of the class file using netbeans.
The solution that worked for me was to create a jar with the correct directory structure for the package (MyValve.jar\org\apache\catalina\connector\) and stick the class file in that directory. I put the jar in the same location (CATALINA_HOME\lib).
I added an entry to the server.xml file inside the <Host> section like this:
<Valve className="org.apache.catalina.connector.MyValve"
classField="value">