Java – Ryan Chapin's Website

[SOLVED] Upgrading Apache Kafka 2.7 to Java 11 Changes authenticationID sent to ZooKeeper Enabling Only 1 Kafka Broker to r/w znodes

Posted on May 17, 2021May 19, 2021 by rchapin

The title of this post is a bit of mouthful and requires a bit more explanation.

I am running a pure open-source version of Kafka (currently running 2.7) and am using SASL/GSSAPI connections between all of the brokers and ZooKeeper. Currently, the whole system, including ZooKeeper, is running Java 8 and it is long-overdue to be upgraded to Java 11.

Upgrading Kafka to Java 11 causes the server to send an incorrect authenticationID String to ZooKeeper which results in the → Continue reading “[SOLVED] Upgrading Apache Kafka 2.7 to Java 11 Changes authenticationID sent to ZooKeeper Enabling Only 1 Kafka Broker to r/w znodes”

message=class configured for SSLContext: sun.security.ssl.SSLContextImpl$TLSContext not a SSLContext When Mocking Static Methods in Class

Posted on March 10, 2021 by rchapin

When mocking static classes with Junit4, Mockito and PowerMock, you may see the following log messages after annotating your test class if the code that you are testing is making HTTP connections:

message=class configured for SSLContext: sun.security.ssl.SSLContextImpl$TLSContext not a SSLContext

Your annotations for the class (or method) typically include the following:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ SomeClassYouWantToMock.class })

This may cause some confusion, especially if whatever other code that you may have ONLY uses HTTP. Add the following to your annotations to tell → Continue reading “message=class configured for SSLContext: sun.security.ssl.SSLContextImpl$TLSContext not a SSLContext When Mocking Static Methods in Class”

How To Spy and Verify a Static Void Method in Java

Posted on February 24, 2021 by rchapin

The Mockito and PowerMockito libraries for JUnit4 are not always the most intuitive.

Following is an example of how to spy and verify a static void method.

    @Test
    public void testAdd() {

        // Prepare the Utils class to be spied.
        PowerMockito.spy(Utils.class);

        // Run the test and get the actual value from the OUT
        int actualValue = App.add("Test1", 1, 1);

        /*
         * To verify the number of times that we called Utils.doSomething we
         * first need to tell the PowerMockito library

→ Continue reading

Mocking Static Methods That Return void in Java

Posted on May 11, 2017January 23, 2021 by rchapin

This is one of those things that I tend to do on a regular basis . . . but unfortunately don’t remember the details each time, so I am adding it for future reference.

Often, developers will want to mock static methods that return void. The Mockito and PowerMockito frameworks provide for this, but the syntax isn’t immediately obvious.

Following is an example.

public class SomeClass {
    public static void doSomething(String arg1, int arg2) {
        // Method that does something...

→ Continue reading

Solution for Executing Native Process from Java that Requires sudo

Posted on December 22, 2016January 28, 2021 by rchapin

If you are building a Java program that requires the ability to execute native commands on the machine which require sudo it requires some additional considerations other than just writing the Java code.

The problem is that sudo, by default, requires a tty for executing sudo such that a password can entered. Even if you configure sudoers to grant NOPASSWD access to a specific command you will still get the following error

sudo: sorry, you must have a tty to

→ Continue reading

Java PowerMock Could not reconfigure JMX java.lang.LinkageError Solution

Posted on August 9, 2016January 28, 2021 by rchapin

If you are using Mockito and PowerMock to build mocks for your Java tests and you run into the following error:

2016-05-05 17:31:20,204 main ERROR Could not reconfigure JMX java.lang.LinkageError: loader constraint violation: loader (instance of org/powermock/core/classloader/MockClassLoader) previously initiated loading for a different type with name "javax/management/MBeanServer"
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
        at org.powermock.core.classloader.MockClassLoader.loadUnmockedClass(MockClassLoader.java:238)
        at org.powermock.core.classloader.MockClassLoader.loadModifiedClass(MockClassLoader.java:182)
        at org.powermock.core.classloader.DeferSupportingClassLoader.loadClass(DeferSupportingClassLoader.java:70)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

Simply add the following as a class level annotation:

@PowerMockIgnore( {"javax.management.*"} )

→ Continue reading “Java PowerMock Could not reconfigure JMX java.lang.LinkageError Solution”

[SOLVED] java.lang.NoSuchMethodError: org.apache.avro.generic.GenericData.createDatumWriter When Using Avro Data with MapReduce

Posted on January 14, 2016January 30, 2021 by rchapin

I am working on a project and have decided to use Avro for the data serialization format.

I encountered the following error when trying to set up the unit test to test the mapper implementation through Eclipse:

java.lang.NoSuchMethodError: org.apache.avro.generic.GenericData.createDatumWriter(Lorg/apache/avro/Schema;)Lorg/apache/avro/io/DatumWriter;
    at org.apache.avro.hadoop.io.AvroSerialization.getSerializer(AvroSerialization.java:114)
    at org.apache.hadoop.io.serializer.SerializationFactory.getSerializer(SerializationFactory.java:82)
    at org.apache.hadoop.mrunit.internal.io.Serialization.copy(Serialization.java:67)
    at org.apache.hadoop.mrunit.internal.io.Serialization.copy(Serialization.java:98)
    at org.apache.hadoop.mrunit.internal.io.Serialization.copyWithConf(Serialization.java:111)
    at org.apache.hadoop.mrunit.TestDriver.copy(TestDriver.java:676)
    at org.apache.hadoop.mrunit.TestDriver.copyPair(TestDriver.java:680)
    at org.apache.hadoop.mrunit.MapDriverBase.addInput(MapDriverBase.java:120)
    at org.apache.hadoop.mrunit.MapDriverBase.addInput(MapDriverBase.java:130)
    at org.apache.hadoop.mrunit.MapDriverBase.addAll(MapDriverBase.java:141)
    at org.apache.hadoop.mrunit.MapDriverBase.withAll(MapDriverBase.java:247)
    at com.ryanchapin.hadoop.mapreduce.mrunit.UserDataSortTest.testMapper(UserDataSortTest.java:111)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)

→ Continue reading

Using the Eclipse Memory Analyzer (MAT) Remotely on Large Heap Dumps

Posted on November 23, 2015January 30, 2021 by rchapin

Sometime your java applilcation will fail and generate an enormous heap dump. One that may be too large to be able to transfer to your local machine and to analyze for lack of RAM, time or both.

One solution is to install the MAT tool on the remote server and generate an HTML output of the analysis to download and view locally. This saves the headache of attempting to get X Windows installed on the remote machine and get all → Continue reading “Using the Eclipse Memory Analyzer (MAT) Remotely on Large Heap Dumps”

Updating all of the pom.xml Version Numbers in a Multi-Module Maven Project

Posted on October 13, 2015February 3, 2021 by rchapin

To update the versions of all of the poms in a multiple module project use the versions-maven plugin.

To update

mvn versions:set -DnewVersion=1.4.0-SNAPSHOT

Will modify all of the versions of each of the poms to the version specified. It will create a pom.xml.versionsBackup for each pom file that it modified. You can then examine each to make sure that it is as you intended.

If you want, you can revert your change with

mvn versions:revert

If you are satisfied with → Continue reading “Updating all of the pom.xml Version Numbers in a Multi-Module Maven Project”

JVM Option for Increasing the Default Number of Lines in the StackTrace

Posted on September 11, 2015February 3, 2021 by rchapin

By default (Java 1.6 or greater), the JVM will output, at most, 1024 lines of the stack trace.

In the situation where you have some recursion problem or some infinite loop that results in a stack overflow error you will need to increase this value with a JVM option to see the origin of your crash.

To do so, add the following option to the java command

$ java -XX:MaxJavaStackTraceDepth=-1 -jar some.jar some.package.Class  etc, etc,

-1 indicates no limit. Any → Continue reading “JVM Option for Increasing the Default Number of Lines in the StackTrace”