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Gradle plugin supporting deployment of your web application to an embedded Tomcat web container

README.md

Gradle Tomcat plugin

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The plugin provides deployment capabilities of web applications to an embedded Tomcat web container in any given Gradle build. It extends the War plugin. At the moment the Tomcat versions 6.x and 7.x are supported.

The typical use case for this plugin is to support deployment during development. The plugin allows for rapid web application development due to the container's fast startup times. Gradle starts the embedded container in the same JVM. Currently, the container cannot be forked as a separate process. This plugin also can't deploy a WAR file to a remote container. If you are looking for this capability, please have a look at the Cargo plugin instead.

Usage

To use the plugin's functionality, you will need to add the its binary artifact to your build script's classpath and apply the plugin.

Adding the plugin binary to the build

The plugin JAR needs to be defined in the classpath of your build script. It is directly available on Bintray. The following code snippet shows an example on how to retrieve it from Bintray:

buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath 'org.gradle.api.plugins:gradle-tomcat-plugin:1.2.3'
    }
}

Provided plugins

The JAR file comes with two plugins:

Plugin Identifier Depends On Type Description
tomcat-base - TomcatBasePlugin Provides Tomcat custom task types, pre-configures classpath.
tomcat tomcat-base TomcatPlugin Provides tasks for starting and stopping an embedded Tomcat container and exposes extension named tomcat.

The tomcat plugin helps you get started quickly. If you are OK if the preconfigured tasks, this is the preferrable option. Most plugin users will go with this option. To use the Tomcat plugin, include the following code snippet in your build script:

apply plugin: 'tomcat'

If you need full control over your tasks or don't want to go with the preconfigured tasks, you will want to use the tomcat-base plugin. That might be the case if you want to set up the container solely for functional testing. The downside is that each task has to be configured individually in your build script. To use the Tomcat base plugin, include the following code snippet in your build script:

apply plugin: 'tomcat-base'

Assigning the Tomcat libraries

Additionally, the Tomcat runtime libraries need to be added to the configuration tomcat. At the moment the Tomcat versions 6.x and 7.x are supported by the plugin. Make sure you don't mix up Tomcat libraries of different versions.

Tomcat 6.x:

repositories {
    mavenCentral()
}

dependencies {
    def tomcatVersion = '6.0.29'
    tomcat "org.apache.tomcat:catalina:${tomcatVersion}",
           "org.apache.tomcat:coyote:${tomcatVersion}",
           "org.apache.tomcat:jasper:${tomcatVersion}"
}

Tomcat 7.x:

repositories {
    mavenCentral()
}

dependencies {
    def tomcatVersion = '7.0.11'
    tomcat "org.apache.tomcat.embed:tomcat-embed-core:${tomcatVersion}",
           "org.apache.tomcat.embed:tomcat-embed-logging-juli:${tomcatVersion}"
    tomcat("org.apache.tomcat.embed:tomcat-embed-jasper:${tomcatVersion}") {
        exclude group: 'org.eclipse.jdt.core.compiler', module: 'ecj'
    }
}

Tasks

The tomcat plugin pre-defines the following tasks out-of-the-box:

Task Name Depends On Type Description
tomcatRun - TomcatRun Starts a Tomcat instance and deploys the exploded web application to it.
tomcatRunWar - TomcatRunWar Starts a Tomcat instance and deploys the WAR to it.
tomcatStop - TomcatStop Stops the Tomcat instance.
tomcatJasper - TomcatJasper Runs the JSP compiler and turns JSP pages into Java source using Jasper.

Project layout

The Tomcat plugin uses the same layout as the War plugin.

Extension properties

The Tomcat plugin exposes the following properties through the extension named tomcat:

  • httpPort: The TCP port which Tomcat should listen for HTTP requests on (defaults to 8080).
  • httpsPort: The TCP port which Tomcat should listen for HTTPS requests on (defaults to 8443).
  • ajpPort: The TCP port which Tomcat should listen for AJP requests on (defaults to 8009).
  • stopPort: The TCP port which Tomcat should listen for admin requests on (defaults to 8081).
  • stopKey: The key to pass to Tomcat when requesting it to stop (defaults to null).
  • enableSSL: Determines whether the HTTPS connector should be created (defaults to false).
  • keystoreFile: The keystore file to use for SSL, if enabled (by default, a keystore will be generated).
  • httpProtocol: The HTTP protocol handler class name to be used (defaults to org.apache.coyote.http11.Http11Protocol).
  • httpsProtocol: The HTTPS protocol handler class name to be used (defaults to org.apache.coyote.http11.Http11Protocol).
  • ajpProtocol: The AJP protocol handler class name to be used (defaults to org.apache.coyote.ajp.AjpProtocol).

Example

The following example code shows how to change the default HTTP/HTTPS ports. To enable SSL we set the property enableSSL to true.

tomcat {
    httpPort = 8090
    httpsPort = 8091
    enableSSL = true
}

Task properties

Furthermore, you can set the following optional task properties:

  • contextPath: The URL context path your web application will be registered under (defaults to WAR name).
  • webDefaultXml: The default web.xml. If it doesn't get defined an instance of org.apache.catalina.servlets.DefaultServlet and org.apache.jasper.servlet.JspServlet will be set up.
  • additionalRuntimeJars: Defines additional runtime JARs that are not provided by the web application.
  • URIEncoding: Specifies the character encoding used to decode the URI bytes by the HTTP Connector (defaults to UTF-8).
  • daemon: Specifies whether the Tomcat server should run in the background. When true, this task completes as soon as the server has started. When false, this task blocks until the Tomcat server is stopped (defaults to false).
  • configFile: The path to the Tomcat context XML file (defaults to src/main/webapp/META-INF/context.xml for tomcatRun, defaults to META-INF/context.xml within the WAR for tomcatRunWar).
  • outputFile: The file to write Tomcat log messages to. If the file already exists new messages will be appended.
  • reloadable: Forces context scanning if you don't use a context file (defaults to true).
  • keystorePass: The keystore password to use for SSL, if enabled.
  • truststoreFile: The truststore file to use for SSL, if enabled.
  • truststorePass: The truststore password to use for SSL, if enabled.
  • clientAuth: The clientAuth setting to use, values may be: true, false or want (defaults to false).

Note: keystoreFile and truststoreFile each require an instance of a File object e.g. file("/path/my.file")

Example

In the following example code, wes declare a custom context file for the task tomcatRun.

tomcatRun.configFile = file('context.xml')

To configure the Jasper compiler task you can choose to set the following properties within the jasper closure of the tomcat extension:

  • validateXml: Determines whether web.xml should be validated (defaults to null).
  • validateTld: Determines whether web.xml should be validated (defaults to null).
  • uriroot: The web application root directory (defaults to src/main/webapp).
  • webXmlFragment: The generated web XML fragment file to be referenced by your web.xml file.
  • addWebXmlMappings: Automatically add the generated web XML fragment to the web.xml file. Caution: this will modify the web.xml file in the project, not the build directory.
  • outputDir: The output directory the compiled JSPs will end up in (defaults to build/jasper).
  • classdebuginfo: Should the class file be compiled with debugging information (defaults to true).
  • compiler: Which compiler Ant should use to compile JSP pages. See the Ant documentation for more information. If the value is not set, then the default Eclipse JDT Java compiler will be used instead of using Ant. No default value.
  • compilerSourceVM: What JDK version are the source files compatible with (defaults to 1.6).
  • compilerTargetVM: What JDK version are the generated files compatible with (defaults to 1.6).
  • poolingEnabled: Determines whether tag handler pooling is enabled. This is a compilation option. It will not alter the behaviour of JSPs that have already been compiled (defaults to true).
  • errorOnUseBeanInvalidClassAttribute: Should Jasper issue an error when the value of the class attribute in an useBean action is not a valid bean class (defaults to true).
  • genStringAsCharArray: Should text strings be generated as char arrays, to improve performance in some cases (defaults to false).
  • ieClassId: The class-id value to be sent to Internet Explorer when using <jsp:plugin> tags (defaults to clsid:8AD9C840-044E-11D1-B3E9-00805F499D93).
  • javaEncoding: Java file encoding to use for generating java source files (defaults to UTF8).
  • trimSpaces: Should white spaces in template text between actions or directives be trimmed (defaults to false).
  • xpoweredBy: Determines whether X-Powered-By response header is added by generated servlet (defaults to false).

Example

tomcat {
    jasper {
        validateXml = true
        webXmlFragment = file("$webAppDir/WEB-INF/generated_web.xml")
        outputDir = file("$webAppDir/WEB-INF/src")
    }
}

FAQ

I get a compile exception when calling a JSP. Is there something I am missing?

The exception you might see is probably similar to this one: org.apache.jasper.JasperException: Unable to compile class for JSP. Tomcat 7.x and 8.x requires you to have Eclipse ECJ 3.6.x in your the classpath. However, this version of the dependency does not exist in Maven Central. You'll have to download that dependency and put it in your own repository or define a repository on your local disk where you can drop it in. Here's an example:

repositories {
     flatDir name: 'localRepository', dirs: 'lib'
}


Why do I get a java.lang.ClassCastException on javax.servlet.Servlet?

Tomcat is very sensitive to having multiple versions of the dependencies javax.servlet:servlet-api and javax.servlet:jsp-api in its classpath. By default they already get pulled in as transitive dependencies of the embedded Tomcat libraries. The exception you might see looks similar to this one:

java.lang.ClassCastException: org.springframework.web.servlet.DispatcherServlet cannot be cast to javax.servlet.Servlet
        at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1062)
        at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1010)
        at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4935)
        at org.apache.catalina.core.StandardContext$3.call(StandardContext.java:5262)
        at org.apache.catalina.core.StandardContext$3.call(StandardContext.java:5257)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
        at java.util.concurrent.FutureTask.run(FutureTask.java:138)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:662)

To fix this make sure you define your JSP and Servlet module dependencies with the scope providedCompile like this:

providedCompile 'javax.servlet:servlet-api:2.5',
                'javax.servlet:jsp-api:2.0'


How do I remote debug my Tomcat started up by the plugin?

If you want to be able to debug your application remotely you have to set the following JVM options in your GRADLE_OPTS environment variable before starting up the container. The port number you choose is up to you.

-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005

Tomcat will then listen on the specified port for incoming remote debugging connections. When starting up the container you should see the following message:

Listening for transport dt_socket at address: 5005

Check your IDE documentation on how to configure connecting to the remote debugging port.


My Tomcat container needs to use a JNDI datasource. How do I set up my project?

First of all you got to make sure to declare the connection pool dependency using the tomcat configuration.

def tomcatVersion = '6.0.35'
tomcat "org.apache.tomcat:dbcp:${tomcatVersion}"

If you decide to go with the default settings place your context.xml in the directory src/main/webapp/META-INF. To set a custom location you can use the convention property configFile. Here's an example on how to set it for the tasks tomcatRun and tomcatRunWar.

[tomcatRun, tomcatRunWar]*.configFile = file('context.xml')

Please refer to the Tomcat documentation for a list of context attributes. The following example shows how to set up a MySQL JNDI datasource.

<?xml version="1.0" encoding="UTF-8"?>
<Context>
    <Resource name="jdbc/mydatabase"
              auth="Container"
              type="javax.sql.DataSource"
              username="superuser"
              password="secretpasswd"
              driverClassName="com.mysql.jdbc.Driver"
              url="jdbc:mysql://localhost:3306/mydb"
              validationQuery="select 1"
              maxActive="10"
              maxIdle="4"/>
</Context>


How do I use hot code deployment with the plugin?

The plugin provides out-of-the-box support for swapping out byte code through the property reloadable. By default this option is turned out so you don't need any additional configuration changes. All you need to do is to have a running instance of the container initiated by tomcatRun. Fire up your favorite editor, change a production source file, save it and recompile your sources in another terminal via gradle compileJava. After a couple of seconds the context is reloaded and you should see the behavior reflected in the terminal window running the container:

Reloading Context with name [/myapp] has started
Reloading Context with name [/myapp] is completed

Alternatively, you can use other commericial byte code swap technologies. The configuration is usually product-specific. Please refer to the product's documentation on how to set it up for your project. The following section describes how to set up Gradle and the plugin with JRebel. First of all download JRebel, install it on your machine and set up the license. To tell JRebel which directory to scan for changed byte code you need to create a rebel.xml file. In your web module place the file under build/classes/main so it can be loaded by the Tomcat plugin. For creating the configuration of the file the Gradle JRebel plugin comes in handy. It's not required to use the plugin. You can also decide to create the configuration by hand. Keep in mind that gradle clean will delete the file. For setting up JRebel in a multi-module project scenario please refer to the documentation. The following code snippet shows an example rebel.xml file.

<?xml version="1.0" encoding="UTF-8"?>
<application xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.zeroturnaround.com"
            xsi:schemaLocation="http://www.zeroturnaround.com http://www.zeroturnaround.com/alderaan/rebel-2_0.xsd">
    <classpath>
        <dir name="/Users/ben/dev/projects/mywebproject/build/classes/main">
        </dir>
    </classpath>

    <web>
        <link target="/">
            <dir name="/Users/ben/dev/projects/mywebproject/src/main/webapp">
            </dir>
        </link>
    </web>
</application>

Edit your Gradle startup script and add the following line to it to tell Gradle to use the JRebel agent. Please make sure to set the environment variable REBEL_HOME that points to your JRebel installation directory.

JAVA_OPTS="-javaagent:$REBEL_HOME/jrebel.jar $JAVA_OPTS"

On startup of your web module using gradle tomcatRun you should see information about the JRebel license being used and the directories being scanned for changes. For our example rebel.xml file it would look like this:

JRebel: Directory '/Users/ben/dev/projects/mywebproject/build/classes/main' will be monitored for changes.
JRebel: Directory '/Users/ben/dev/projects/mywebproject/src/main/webapp' will be monitored for changes.

If a file has been recompiled JRebel indicates this by writing it to the console like this:

JRebel: Reloading class 'de.muschko.web.controller.TestController'.


In need to run in-container integration tests as part of my build. What needs to be done?

Usually unit and integration tests are kept separate by convention. One convention could be to name the test source files differently e.g. integration tests always end with the suffix IntegrationTest, unit test files end with Test. By doing that you can run them separately. For running the integration tests you will want to run the Tomcat task as daemon thread and shut it down once your tests are done. The following example demonstrates how to set up a Gradle task that provides this functionality. Of course this is only one way of doing it. The following example requires Gradle >= 1.7:

apply plugin: 'tomcat-base'

ext {
    tomcatStopPort = 8081
    tomcatStopKey = 'stopKey'
}

task integrationTomcatRun(type: org.gradle.api.plugins.tomcat.tasks.TomcatRun) {
    stopPort = tomcatStopPort
    stopKey = tomcatStopKey
    daemon = true
}

task integrationTomcatStop(type: org.gradle.api.plugins.tomcat.tasks.TomcatStop) {
    stopPort = tomcatStopPort
    stopKey = tomcatStopKey
}

task integrationTest(type: Test) {
    include '**/*IntegrationTest.*'
    dependsOn integrationTomcatRun
    finalizedBy integrationTomcatStop
}

test {
    exclude '**/*IntegrationTest.*'
}
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