'No main manifest attribute' error with Maven + TestNG + Selenium Grid2

Question

I wants to run Selenium grid hub, With my project framework Maven + TestNG.

I have added selenium-server 3.12 dependency in POM.XML and When I call this selenium-server jar from our maven project, its gives me error as 'No main manifest attribute'.

I am having Doubt, to call "java -jar selenium-server-standalone-3.12.0.jar -role hub" Do we need to externally download this Jar for Selenium Hub ? As its already imported in Maven project.

Error with Maven project setup,'No main manifest attribute'

C:\Users\Desktop-pc>java -jar org\seleniumhq\selenium\selenium-server\3.12.0\selenium-server-3.12.0.jar -role hub
no main manifest attribute, in org\seleniumhq\selenium\selenium-server\3.12.0\selenium-server-3.12.0.jar

Where if I use separate 'Selenium Server Standalone' jar, hub is created successfully:

C:\>java -jar selenium-server-standalone-3.8.1.jar -role hub
16:05:07.614 INFO - Selenium build info: version: '3.8.1', revision: '6e95a6684b'
16:05:07.616 INFO - Launching Selenium Grid hub
2018-05-28 16:05:08.690:INFO::main: Logging initialized @1490ms to org.seleniumhq.jetty9.util.log.StdErrLog
16:05:08.707 INFO - Will listen on 4444
2018-05-28 16:05:08.823:INFO:osjs.Server:main: jetty-9.4.7.v20170914
2018-05-28 16:05:08.867:INFO:osjs.session:main: DefaultSessionIdManager workerName=node0
2018-05-28 16:05:08.868:INFO:osjs.session:main: No SessionScavenger set, using defaults
2018-05-28 16:05:08.871:INFO:osjs.session:main: Scavenging every 660000ms
2018-05-28 16:05:08.876:INFO:osjsh.ContextHandler:main: Started o.s.j.s.ServletContextHandler@1672fe87{/,null,AVAILABLE}
2018-05-28 16:05:11.946:INFO:osjs.AbstractConnector:main: Started ServerConnector@1816a71f{HTTP/1.1,[http/1.1]}{0.0.0.0:4444}
2018-05-28 16:05:11.948:INFO:osjs.Server:main: Started @4748ms
16:05:11.948 INFO - Nodes should register to http://localhost:4444/grid/register/
16:05:11.949 INFO - Selenium Grid hub is up and running

POM.XML

       <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass> ???? </mainClass>
                        </manifest>
                    </archive>
                </configuration>
       </plugin>

what I need to declare in mainclass, If I am using @TestNG and its without static main class method.

Answer 1

Selenium Grid is usually used for remote executions so that your local machine doesn't have to have browsers installed (true in the case of build machines which are usually headless linux boxes) or so that you can use your local machine for something else (true in the case of your local laptop/desktop when you are running tests in development mode).

Binding the Selenium Grid within your project (such that every time you build and run tests in your project a selenium grid is spun off) is not such a good idea.

If you are still looking for starting a Selenium Grid locally (starting a Selenium Grid remotely is not only hackish but also requires a lot of workarounds and is susceptible to a lot of failures) first and then having your UI tests point at it and then executed, you can do it in the following ways:

• By spinning off a Selenium Grid via a maven plugin.

For doing this you would need to leverage the maven-antrun-plugin. Below is a typical configuration of how the antrun-plugin would look like (It spins off a hub with 2 nodes wired to it ) Source for this info was this thread

<build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-antrun-plugin</artifactId>
        <version>1.7</version>
        <executions>
          <execution>
            <phase>process-test-classes</phase>
            <configuration>
              <target>
                <java classname="org.openqa.grid.selenium.GridLauncherV3"
                  classpathref="maven.test.classpath"
                  failonerror="true"
                  fork="false">
                  <arg line="-role hub"/>
                </java>
                <java classname="org.openqa.grid.selenium.GridLauncherV3"
                  classpathref="maven.test.classpath"
                  failonerror="true"
                  fork="false">
                  <arg line="-role node"/>
                </java>
                <java classname="org.openqa.grid.selenium.GridLauncherV3"
                  classpathref="maven.test.classpath"
                  failonerror="true"
                  fork="false">
                  <arg line="-role node -port 6666"/>
                </java>
              </target>
            </configuration>
            <goals>
              <goal>run</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
</build>

The above plugin configuration assumes that selenium-server is added as a test dependency i.e., something like below

<dependency>
  <groupId>org.seleniumhq.selenium</groupId>
  <artifactId>selenium-server</artifactId>
  <version>3.12.0</version>
  <scope>test</scope>
</dependency>

If you have a compile time dependency on selenium-server then please change

classpathref="maven.test.classpath"

To

classpathref="maven.compile.classpath"

For more details on classpathref please refer to the official documentation.

Caveat:

Since now the Selenium Grid basically registers beans for JMX, you may get an error such as the one below

08:28:09.529 INFO [GridLauncherV3$3.launch] - Launching a Selenium Grid node on port 6666
java.security.AccessControlException: access denied ("javax.management.MBeanTrustPermission" "register")
    at java.security.AccessControlContext.checkPermission(AccessControlContext.java:472)

In case you get such an error, please make sure that you open up the file named java.policy found under %JAVA_HOME%\jre\lib\security\ and within the grant { section add permission javax.management.MBeanTrustPermission "register"; (Source for this info was this thread)

Now you can very well run your TestNG tests by running mvn clean test (And when you do that, you will notice a selenium grid being spun off locally)

• By spinning off a Selenium Grid via a TestNG listener/configuration method.

Here you would basically be spinning off a selenium hub and node either via a TestNG listener or via a configuration method and then have your tests just point at the locally spun off grid and run against it.

The below sample shows a test that runs against a locally spun off grid (via a configuration method)

import java.net.MalformedURLException;
import java.net.URL;
import java.util.concurrent.TimeUnit;
import org.openqa.grid.selenium.GridLauncherV3;
import org.openqa.selenium.chrome.ChromeOptions;
import org.openqa.selenium.remote.RemoteWebDriver;
import org.testng.annotations.AfterClass;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.BeforeSuite;
import org.testng.annotations.Test;

public class AnotherSample {
  private RemoteWebDriver driver;

  @BeforeSuite
  public void beforeSuite() throws InterruptedException {
    new Thread(
            () -> {
              String[] args = {"-role", "hub"};
              GridLauncherV3.main(args);
            })
        .start();
    new Thread(
            () -> {
              String[] args = {"-role", "node"};
              GridLauncherV3.main(args);
            })
        .start();
    // Lets wait for 10 seconds for the Hub and the node to be up and running
    TimeUnit.SECONDS.sleep(10);
  }

  @BeforeClass
  public void setup() throws MalformedURLException {
    driver =
        new RemoteWebDriver(new URL("http://localhost:4444/wd/hub"), new ChromeOptions());
  }

  @Test
  public void testMethod() {
    driver.get("http://www.google.com");
    System.err.println("Title = " + driver.getTitle());
  }

  @AfterClass
  public void cleanup() {
    if (driver != null) {
      driver.quit();
    }
  }
}

Answer 2

You are using maven-jar-plugin which is used to create jar artifact for a normal java project.

In order to run testNG annotated java method classes , you require maven-surefire-plugin. Remove the maven-jar-plugin and replace it with following plugin block.

             <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.16</version>
                <configuration>
                    <skip>false</skip>
                    <testFailureIgnore>true</testFailureIgnore>
                </configuration>
            </plugin>

Answer 3

Without your detailed usecase I am not sure about your exact requirement. But,

• To start the Selenium Server you need to issue the command as:

  java -jar selenium-server-standalone-3.12.0.jar
  

• To start the Selenium Grid Hub you need to issue the command as:

  java -jar selenium-server-standalone-3.12.0.jar -role hub
  

• If you are using DefaultSelenium (or the RemoteWebDriver implementation)you still need to start a Selenium Server and there are two possible ways to achieve it as follows:

  • The best way is to download the selenium-server-standalone.jar from the Selenium Downloads page and just use it.

  • Alternatively, you can also embed the Selenium Server into your own project by adding the following dependency to your pom.xml:

    <dependency>
        <groupId>org.seleniumhq.selenium</groupId>
        <artifactId>selenium-server</artifactId>
        <version>3.12.0</version>
    </dependency>  
    

  Now you can create a Selenium Server instance yourself and start it.

Note: Be aware, that the selenium-server artifact has a dependency to the servlet-api-3.x.y artifact, which you should exclude, if your project will be run inside a web application container.

Here you will find the Maven Information on Selenium.

---

Update

If you are trying to run it from the CLI you need to provide the command:

java -jar selenium-server-standalone-3.12.0.jar

The -jar option works only if the JAR file is an executable JAR file which essentially means it must have a manifest file with a Main-Class attribute in it.

You can find more details in Packaging Programs in JAR Files to create an executable JAR.

If the JAR isn't following these rules it is not an executable jar.

If it's not an executable JAR then you need to run the program as follows:

java -cp selenium-server-standalone-3.12.0.jar com.somepackage.SomeClass

where com.somepackage.SomeClass is the Class that contains the main method to run the program.

You can find a similar discussion in Can't execute jar- file: “no main manifest attribute”.