Develop Reference

Getting a specific version of an image with Jib (Maven, Docker, testcontainers)

I'm trying to understand a comment that a colleague made. We're using testcontainers to create a fixture:
import org.testcontainers.containers.GenericContainer;
import org.testcontainers.utility.DockerImageName;
public class SalesforceFixture extends GenericContainer<SalesforceFixture> {
private static final String APPLICATION_NAME = "salesforce-emulator";
public SalesforceFixture() {
// super(ImageResolver.resolve(APPLICATION_NAME));
super(DockerImageName.parse("gcr.io/ad-selfserve/salesforce-emulator:latest"));
...
}
...
The commented code is what it used to be. The next line is my colleague's suggestion. And on that line he commented:
This is the part I don't know. The [ImageResolver] gets the specific version of the emulator, rather than the latest. You need a docker-info file for that though, which jib doesn't automatically generate (but I think it can).
This is what I know or have figured so far:
SalesforceFixture is a class that will be used by other projects to write tests. It spins up a container in Docker, running a service that emulates the real service's API. It's like a local version of the service that behaves enough like the real thing that if one writes code and tests using the fixture, it should work the same in production. (This is where my knowledge ends.)
I looked into ImageResolver—it seems to be a class we wrote that searches a filesystem for something:
public static String resolve(String applicationName, File... roots) {
Stream<File> searchPaths = Arrays.stream(roots).flatMap((value) -> {
return Stream.of(new File(value, "../" + applicationName), new File(value, applicationName));
});
Optional<File> buildFile = searchPaths.flatMap((searchFile) -> {
if (searchFile.exists()) {
File imageFile = new File(searchFile + File.separator + "/target/docker/image-name");
if (imageFile.exists()) {
return Stream.of(imageFile);
}
}
return Stream.empty();
}).findAny();
InputStream build = (InputStream)buildFile.map(ImageResolver::fileStream).orElseGet(() -> {
return searchClasspath(applicationName);
});
if (build != null) {
try {
return IOUtils.toString(build, Charset.defaultCharset()).trim();
} catch (IOException var6) {
throw new RuntimeException("An exception has occurred while reading build file", var6);
}
} else {
throw new RuntimeException("Could not resolve target image for application: " + applicationName);
}
}
But I'm confused. What filesystem? Like, what is the present working directory? My local computer, wherever I ran the Java program from? Or is this from within some container? (I don't think so.) Or maybe the directory structure inside a .jar file? Or somewhere in gcr.io?
What does he mean about a "specific version number" vs. "latest"? I mean, when I build this project, whatever it built is all I have. Isn't that equivalent to "latest"? In what case would an older version of an image be present? (That's what made me think of gcr.io.)
Or, does he mean, that in the project using this project's image, one will not be able to specify a version via Maven/pom.xml—it will always spin up the latest.
Sorry this is long, just trying to "show my work." Any hints welcome. I'll keep looking.

I can't comment on specifics of your own internal implementations, but ImageResolver seems to work on your local filesystem, e.g. it looks into your target/ directory and also touches the classpath. I can imagine this code was just written for resolving an actual image name (not an image), since it also returns a String.
Regarding latest, using a latest tag for a Docker image is generally considered an anti-pattern, so likely your colleague is commenting about this. Here is a random article from the web explaining some of the issues with latest tag:
https://vsupalov.com/docker-latest-tag/
Besides, I don't understand why you ask these questions which are very specific to your project here on SO rather than asking your colleague.

How can I work around YouTube API embed restrictions like other websites?

I am building a java program that has the option to play YouTube videos in an embedded player.
The problem is that most of the music videos won't play and I get the following error:
"This video contains content from (Media Corporation Name). It is restricted from playback on certain sites."
I tried loading the same URL in Chrome and got the same results.
https://www.youtube.com/embed/TMZi25Pq3T8
However, after some research, I quickly got it fixed by installing a Chrome Extension that allows me to add HTTP Request Headers and added a Referer header that follows this structure "https://www..com" and got it working.
So I thought that must be it.
I added the following code in order to add request headers to my JavaFX WebView / WebEngine:
URI uri = URI.create("https://www.youtube.com/embed/TMZi25Pq3T8");
List<String> cookies = new ArrayList<>();
cookies.add("User-Agent=BDM/v0.92");
cookies.add("Referer=https://www.youtube.com");
Map<String, List<String>> headers = new LinkedHashMap<String, List<String>>();
headers.put("Set-Cookie", cookies);
try {
CookieHandler.getDefault().put(uri, headers);
} catch (IOException ex) {
ex.printStackTrace();
}
System.out.println(webView.getEngine().getUserAgent());
webView.getEngine().load(uri.toString());
Still, no success, the same error message.
The website that I'm using to extract data about releases through their API, Discogs, is able to play "restricted" videos as well. What am I missing here?
LATER EDIT:
Further clarifications:
I would like to apologize for the mistakes I made:
The line System.out.println(webView.getEngine().getUserAgent()); doesn't print "BDM/v0.92" as I first stated, it prints the default JavaFX user agent, "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/538.19 (KHTML, like Gecko) JavaFX/8.0 Safari/538.19". And this leads to number 2
As Roman Nazarenko pointed out, I was confusing cookies with request headers.
This leads to the real question, how can I send HTTP Request headers for JavaFX WebEngine? The only option is to set the user agent by calling webView.getEngine().setUserAgent("myUserAgent");
I found a hack here but this didin't work for me: https://twitter.com/codingfabian/status/524942996748652544
Thanks!

I managed to solve the issue by using javassist and this tutorial on how to instrument Java code.
As I stated in my question, the YouTube player needs a Referer header to play some videos (like music videos owned by VEVO, Sony Music Enternatinment, etc.).
What I did is I intercepted prepareConnection method from the URLLoader class that is used by JavaFX's WebEngine and inserted my instruction at the top of the method body:
c.setRequestProperty("Referer", "https://www.discogs.com");
(Again, please follow the tutorial for all the instructions)
(Note: Even though the tutorial above is explains very well the concepts, it doesn't really touch much on the role and structure of a MANIFEST.MF file, so please check this link for more info about this aspect)
These are my two classes:
MyJavaAgent.java
package com.busytrack.discographymanager.headerfixagent;
import java.lang.instrument.Instrumentation;
public class MyJavaAgent {
public static void premain(String agentArgument, Instrumentation instrumentation) {
ClassTransformer transformer = new ClassTransformer();
instrumentation.addTransformer(transformer);
}
}
ClassTransformer.java
package com.busytrack.discographymanager.headerfixagent;
import java.io.ByteArrayInputStream;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;
public class ClassTransformer implements ClassFileTransformer {
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
byte[] byteCode = classfileBuffer;
if (className.equals("com/sun/webkit/network/URLLoader")) {
try {
ClassPool classPool = new ClassPool(true);
CtClass ctClass = classPool.makeClass(new ByteArrayInputStream(classfileBuffer));
CtMethod method = ctClass.getDeclaredMethod("prepareConnection");
String src = "$1.setRequestProperty(\"Referer\", \"https://www.discogs.com\");"; // Confused about there being "$1" instead of "c"? Please read below
method.insertBefore(src);
byteCode = ctClass.toBytecode();
ctClass.detach();
} catch (Exception e) {
e.printStackTrace();
}
}
return byteCode;
}
}
This is why I used "$1" to access the method parameter, instead of "c":
The statement and the block can refer to fields and methods. They can also refer to the parameters to the method that they are inserted into if that method was compiled with the -g option (to include a local variable attribute in the class file). Otherwise, they must access the method parameters through the special variables $0, $1, $2, ... described below. Accessing local variables declared in the method is not allowed although declaring a new local variable in the block is allowed.
The entire javassist tutorial can be found here.
After packing the two classes and the MANIFEST.MF file in a separate JAR, import it in your IDE (I used Eclipse) and add the following VM argument:
-javaagent:./(your-jar-name).jar
In Eclipse, you can add VM arguments like this:
right click on your project -> Run As -> Run Configurations... -> open the Arguments tab -> insert your VM argument -> Apply
I hope this helps someone out there. I know I spent a few days on this issue.
I don't know if this is the best approach but it does the job for me.
Still, it makes me wonder why isn't there a straightforward way of setting Request Headers for JavaFX's WebEngine...
Later edit:
I found a much cleaner and easier approach for loading Java Agents, dynamically, without the need to create a separate JAR, manifest file, importing them, passing the -javaagent VM parameter at startup, etc.
I used the ea-agent-loader (JAR download link).
Import the JAR in your IDE and change the MyJavaAgent class (the one that had the premain method) to this:
package com.busytrack.discographymanager.headerfixagent;
import java.lang.instrument.Instrumentation;
public class MyJavaAgent {
public static void agentmain(String agentArgument, Instrumentation instrumentation) {
ClassTransformer transformer = new ClassTransformer();
instrumentation.addTransformer(transformer);
}
}
My main method from the MainClass looks like this:
public static void main(String[] args) {
AgentLoader.loadAgentClass(MyJavaAgent.class.getName(), null); // Load the MyJavaAgent class
launch(args); // Start the JavaFX application
}
I wanted to be able to load the Agent dynamically because, using the static method required me to create separate launchers for all platforms and pass the -javaagent parameter on startup. Now, I can export a runnable JAR from eclipse like I usually do and the agent will load automatically (no VM parameters required). Thanks, BioWare for this tool! :D

Opening a TCL gui within Java code

I have a TCL file which uses Tcl's BWidget package that I've been using as a GUI for my program. I now want to be able to load up this GUI from a separate Java program. I've looked into Jacl and Swank, but they don't seem to do exactly what I want.
I've tried the following with Jacl but it's unable to evaluate the file. While debugging, I can see that it completes parsing my tcl file, but it throws an exception while parsing through the BWidget package tcl files. Here's my Java code:
Interp interp = new Interp();
try {
interp.evalFile("C:\\CTP\\Tcl\\LuxonCtp32.tcl");
} catch (TclException ex) {
int code = ex.getCompletionCode();
System.err.println("command returned bad error code: " + code);
} finally {
interp.dispose();
}
Any ideas on how I can accomplish what I want to do? Is it even possible?

Tcl itself can not display a GUI. It uses a plugin called Tk for that.
In the C reference implementation of Tcl you get Tk as well.
Tk has not been ported to Java, Tcl has.
You can not use Jacl to display Tk widgets, but TclBlend could do that, because TclBlend uses the C reference implementation of Tcl. That means that the user needs a working Tcl/Tk installation.
There are some problems with TclBlend and Tcl > 8.5 through, which result in a segfault.
IIRC you have to remove the conditional if around Tcl_FindNameOfExecutable in TclBlends C code (and compile it yourself).

Go to this site http://jtcl-project.github.io/jtcl/ and download now for the binary zip. Its a recent java tcl on github called Jtcl.
Unzip it and you will find a jar called jtcl-2.7.0.jar.
I am using Netbeans 8 my preference.
I add the jar into Project Library.
I create a java file called JTclHallo.java and this is the code.
package jtclhallo;
// import tcl.lang it belongs to jtcl-2.7.0 jar a must
import tcl.lang.*;
// Java wrapper to test JACL or JTCL.
public class JTclHallo {
public static void main(String []args) {
//Interp is a java class belonging to tcl.lang. Unrar the jtcl-2.7.0
Interp i = new Interp();
try {
//call your tcl file mine was swing.tcl from the E drive
i.eval("source E:/private/swing.tcl");
} catch (TclException e) {
System.out.println("Exception: " + e.getMessage());
}
}
}
For swing.tcl
package require java
set window [java::new javax.swing.JFrame]
$window setSize 600 400
$window setVisible true

Flyway - oracle PL/SQL procedures migration

What would be the preferable way to update schema_version table and execute modified PL/SQL packages/procedures in flyway without code duplication?
My example would require a class file be created for each PL/SQL code modicaition
public class V2_1__update_scripts extends AbstractMigration {
// update package and procedures
}
AbstractMigration class executes the files in db/update folder:
public abstract class AbstractMigration implements SpringJdbcMigration {
private static final Logger log = LoggerFactory.getLogger(AbstractMigration.class);
#Override
public void migrate(JdbcTemplate jdbcTemplate) throws Exception {
Resource packageFolder = new ClassPathResource("db/update");
Collection<File> files = FileUtils.listFiles(packageFolder.getFile(), new String[]{"sql"}, true);
for (File file : files ) {
log.info("Executing [{}]", file.getAbsolutePath());
String fileContents = FileUtils.readFileToString(file);
jdbcTemplate.execute(fileContents);
}
}
}
Is there any better way of executing PL/SQL code?

I wonder if it's better to duplicate the code into the standard migrations folder. It seems like with the given example you wouldn't then be able to migrate up to version N of the db, as some prior version would execute all the current version of the pl/sql. I'd be interested to see if you settled on a solution for this.

There is no built-in support or other command you have missed.
Of the top of my head, I would think about either the way you presented here or using a generator to produce new migration sql files after an SCM commit.
Let's see if someone else found a better solution.

The version of Flyway current at the time of this writing (v4.2.0) supports the notion of repeatable scripts designed specifically for such situations. Basically any script with a "Create or replace" semantic is a candidate.
Simply name your script as R__mypackage_body.sql or whatever prefix you wish for repeatable scripts. Please see Sql-based migrations and Repeatable migrations for further information.

Prevent “Send error report to Microsoft”

I'm working on java application which perform some Runtime sub-process on files, for some files I got error cause the Send error report to Microsoft window to appear ,I need to handle this error programmatically, without showing this window to user. Please can anyone help ?

To Suppress windows error reporting the .exe that is being invoked should not terminate with an unhandled exception. This only works if you have access to the source of the application.
Based on the WER Reference - you should use the Win32 API call WerAddExcludedApplication to add the specific .exe files that you are intending to ignore to the per-user ignore list - you could create a simple stub-application that allows you to add applications by name to the ignore list. Then when you invoke the application it does not trigger the error.
Similarly you could create another application to remove them using the WerRemoveExcludedApplication.
Alternatives are to use JNI/JNA to make a class to encapsulate this functionality rather than using Runtime.exec
Here is a simple example using Java Native Access (JNA), which is a simpler version of JNI (no C++ needed for the most part). Download the jna.jar and make it part of your project.
import com.sun.jna.Native;
import com.sun.jna.WString;
import com.sun.jna.win32.StdCallLibrary;
public class JNATest {
public interface CLibrary extends StdCallLibrary {
CLibrary INSTANCE = (CLibrary) Native.loadLibrary("wer.dll",
CLibrary.class);
int WerAddExcludedApplication(WString name, boolean global);
int WerRemoveExcludedApplication(WString name, boolean global);
}
public static void main(String[] args) {
CLibrary.INSTANCE.WerAddExcludedApplication(new WString("C:\\foo.exe"), false);
CLibrary.INSTANCE.WerRemoveExcludedApplication(new WString("C:\\foo.exe"), false);
}
}
Basically, replace the new WString(...) value with the name of the application that you are intending to ignore. It should be ignored for the purposes of windows error reporting at that point.
Bear in mind that the wer.dll is only on Windows Vista and newer, so if this is a problem, then you may need to edit the registry entries manually.

You can always use try-catch-finally statement:
try
{
some code here (the code that is causing the error);
}
catch (Exception x)
{
handle exception here;
}
It works for me...
EDIT Here is the link that can help you a little bit more:
http://www.exampledepot.com/egs/Java%20Language/TryCatch.html