How to create an Undertow Handler in JBoss EAP 7

Environment

Red Hat JBoss Enterprise Application Platform (EAP) 7

Issue

• How to create an Undertow Handler in JBoss EAP 7
• Tomcat/JBossWeb Valve is not supported in EAP 7 and Undertow Handler needs to be used instead of valve in EAP 7. How can we create an Undertow Handler?

Resolution

1. Create a custom handler that implements io.undertow.server.HttpHandler

package com.redhat.jboss.support.example;

import io.undertow.server.HttpHandler;
import io.undertow.server.HttpServerExchange;
import java.util.logging.Logger;

public class UndertowExampleHandler implements HttpHandler {

    private static final Logger LOGGER = Logger.getLogger(UndertowExampleHandler.class.getName());
    private static final String DEFAULT_MESSAGE = "Hello, World!";
    private String message;

    private HttpHandler next;

    public UndertowExampleHandler(HttpHandler next) {
        message = DEFAULT_MESSAGE;
        this.next = next;
    }

    @Override
    public void handleRequest(final HttpServerExchange exchange) throws Exception {
        LOGGER.info("handleRequest() is called");
        LOGGER.info("message = " + this.getMessage());
        LOGGER.info("requestPath = " + exchange.getRequestPath());
        next.handleRequest(exchange);
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String str) {
        LOGGER.info("setMessage() is called: str = " + str);
        if (str != null && !str.isEmpty()) {
            this.message = str;
        }
    }
}

2. Create a JBoss Module that contains the jar with the Handler class

Execute the following JBoss CLI commands below, which do the followings:

• Create a custom module named examples.undertow.handler containing the jar undertow-example-handler.jar which has the ExampleHandler.
• Define the custom-filter in the undertow filters section.
• Add the filter-ref to the undertow host which you want it to be applied.

# Install the module
# Depends on Java/Java EE API and Undertow Core API
module add --name=com.redhat.jboss.support.example.undertow.handler --slot=main --resources=jboss-undertow-example-handler.jar --dependencies=io.undertow.core,javaee.api,javax.api

# add the handler to undertow subsystem
/subsystem=undertow/configuration=filter/custom-filter=example-handler:add(class-name=com.redhat.jboss.support.example.UndertowExampleHandler, module=com.redhat.jboss.support.example.undertow.handler)

# (Optional) add a parameter to the handler
# /subsystem=undertow/configuration=filter/custom-filter=example-handler:write-attribute(name=parameters.message,value=test)

# add the filter ref to the host to enable it
/subsystem=undertow/server=default-server/host=default-host/filter-ref=example-handler:add()

The module add command above results in this $JBOSS_HOME/modules/com/redhat/jboss/support/example/undertow/handler/main/module.xml:

<?xml version="1.0" ?>
<module xmlns="urn:jboss:module:1.1" name="com.redhat.jboss.support.example.undertow.handler" slot="main">
    <resources>
        <resource-root path="jboss-undertow-example-handler.jar"/>
    </resources>
    <dependencies>
        <module name="io.undertow.core"/>
        <module name="javaee.api"/>
        <module name="javax.api"/>
    </dependencies>
</module>

The CLI commands add the fliter and filter-ref to the undertow subsystem such as:

    <subsystem xmlns="urn:jboss:domain:undertow:3.1">
        ...
        <server name="default-server">
            ...
            <host name="default-host" alias="localhost">
                ...
                <filter-ref name="example-handler"/>
            </host>
        </server>
        ...
        <filters>
            ...
            <filter name="example-handler" module="com.redhat.jboss.support.example.undertow.handler" class-name="com.redhat.jboss.support.example.UndertowExampleHandler">
                <param name="message" value="test"/>
            </filter>
        </filters>
    </subsystem>

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