Java Posts

Does JBoss EAP’s “org.jboss.jca.adapters.jdbc.extensions.oracle.OracleValidConnectionChecker” doing a “Select 1 from Dual”?

02 Jan , 2020 No Comments

TL;DR
No it is NOT.

Longer Version :
JBoss EAP and Wildfly have its own internal query validator to check whether connection is active or not before doing connection to Oracle database, it resides on below class.

org.jboss.jca.adapters.jdbc.extensions.oracle.OracleValidConnectionChecker

Why i’m interested in OracleValidConnectionChecker class? Because several days ago, i got a critical question from Habiburrokhman Sjarbini, my fellow RedHat Platform Consultant regarding this. Whether OracleValidConnectionChecker which is embedded in JBoss EAP will do a “select 1 from dual” query?

I have to decompile a lot of classes to see what is running under the hood,

Here is the screenshot of what OracleValidConnectionChecker looks like,

On Oracle database, it will call “oracle.jdbc.driver.OracleConnection” and invoke method “pingDatabase”. Lets check what is the content of “pingDatabase” method,

OracleConnection will call its super class, OracleConnectionWrapper, and invoke pingDatabase method. It goes here and there, until finally it reach oracle.jdbc.driver.PhysicalConnection class on method doPingDatabase.

And as you can see, it runs a “SELECT ‘x’ FROM DUAL” query, instead on “select 1 from dual”. :)

Jar versions :

ojdbc8.jar
ironjacamar-jdbc-1.4.11.Final.jar
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Slowness when Generating SecureRandom with Java on RHEL 7

20 Dec , 2019 No Comments

Today i had a very weird issue where there is slowness on my app when generating random secure number on my server, the weird thing is that it never happen on my Windows machine. After intensive debugging i found out that below code part is causing the slowness,

    static {
        try {
            secureRandom = SecureRandom.getInstanceStrong();
        } catch (Exception e) {
            secureRandom = new SecureRandom();
        }
    }

Replacing it with below code solve my problem,

    static {
        try {
            secureRandom = SecureRandom.getInstance("SHA1PRNG");
        } catch (Exception e) {
            secureRandom = new SecureRandom();
        }
    }
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Deploying Spring Boot with A Dynamic application.properties Location to Openshift

14 Dec , 2019 No Comments

I want to create a simple spring boot app, and deploy it to Openshift 4.2. It supposed to be a straigh forward task, but the problem is that it is required to externalize all configuration to a configmaps or secret so no need to recompile the whole app in case of configuration change.

There are several approach of externalizing configuraton to configmaps, one way is put it as a string literal, include on your pod and call on application via environment variables, or deploy the whole configuration file and mount it on your Openshift pod. The last approach is the one that we will be doing now today.

First lets start with deploying our properties to Openshift as configmaps,

oc create cm myapp-api-configmap --from-file=D:\source\my-app\src\main\resources\application.properties

We can check and validate the result,

oc get cm

oc describe cm myapp-api-configmap

After that, we can mount corresponding configmap to a specific folder on our Pod, on below example modification is done on DeploymentConfig.yaml and mounting application.properties to /deployments/config folder.

kind: DeploymentConfig
apiVersion: apps.openshift.io/v1
metadata:
  ........
    spec:
      volumes:
        - name: myapp-api-configmap-volume
          configMap:
            name: myapp-api-configmap
            defaultMode: 420
      containers:
        - name: myapp-api
          image: >-
            image-registry.openshift-image-registry.svc:5000/openshift/myapp@sha256:1127.....
          ports:
            - containerPort: 8778
              protocol: TCP
            - containerPort: 8080
              protocol: TCP
            - containerPort: 8443
              protocol: TCP
          resources: {}
          volumeMounts:
            - name: myapp-api-configmap-volume
              mountPath: /deployments/config
          terminationMessagePath: /dev/termination-log
          terminationMessagePolicy: File
          imagePullPolicy: Always
      restartPolicy: Always
      terminationGracePeriodSeconds: 30
      dnsPolicy: ClusterFirst
      securityContext: {}
      schedulerName: default-scheduler

A modification is also needed on my Dockerfile, pointing a new path for my properties file by using “spring.config.location” parameter,

FROM registry.access.redhat.com/openjdk/openjdk-11-rhel7

USER jboss
RUN mkdir -p /deployments/image && chown -R jboss:0 /deployments
EXPOSE 8080

COPY target/application-1.0.jar /deployments/application.jar
CMD ["java", "-jar", "/deployments/application.jar", "--spring.config.location=file:///deployments/config/application.properties"]

Build, deploy,and see that application is now taking configuration from external configuration file.

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How to Connect and Uploading Files to Openstack using Java

29 Nov , 2019 No Comments

Currently im involved in a project where i have to use OpenStack Object Store for storing images and files. After Googling for a while, i come up with a solution of using JOSS library to connect to OpenStack, despite OpenStack provide REST API to connect to it directly.

But first, we need to see the API URL that is needed for login to OpenStack. And it can be seen on below screenshot, inside the red box.

After we got the url, next is importing JOSS library to be used in our app. We can import it by using a simple maven command,

<dependency>
	<groupId>org.javaswift</groupId>
	<artifactId>joss</artifactId>
	<version>0.10.2</version>
</dependency>

And a simple java file, to do a simple upload using a provided credential.

@Test
public void uploadImageToDCTest() {
	AccountConfig config = new AccountConfig();
	config.setAuthenticationMethod(AuthenticationMethod.KEYSTONE_V3);
	config.setUsername("user");
	config.setPassword("password");
	config.setAuthUrl("https://osphdc.server01.com:13000/v3/auth/tokens");
	config.setTenantName("default");

	Account account = new AccountFactory(config).createAccount();

	Container container = account.getContainer("images");
	if(!container.exists()) {
		container.create();
		container.makePublic();
	}

	StoredObject object = container.getObject("jenkins-logo.png");
	object.uploadObject(new File("D:\\jenkins-logo.png"));
	System.out.println("Public URL: "+object.getPublicURL());
}

Later on, we can check the result on our OpenStack object store page.

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[Keycloak] How to Solve “/openid-connect/userinfo” which Gives JWT Response instead of A Simple JSON

25 Nov , 2019 No Comments

Previously expecting a json response from “/openid-connect/userinfo” API , such as below screenshot,

But suddenly someone change configuration somewhere which makes previous response changed into,

Took quite sometime for me to findout which part of Kecloak configuration which makes this happens. Finally i found the proper configuration, it is located on “Fine Grain OpenID Connect Configuration”. Previously it is “RS512”, changing into “unsigned” solve my problem.

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