Debug Java program by executing "gradle run"

Question

I have a Gradle project in Eclipse IDE and I usually use the option gradle run to run my Java application.

I have an error in my Java code and I want to debug it, but when I execute gradle run, the debugger doesn't stop in the breakpoints. In the "Debug as" menu, I don't have anything like gradle debug.

How can I debug my application?

There is a discussion on discuss.gradle.org/t/… on how to debug in eclipse using gradle tasks. — frhd
– frhd, Commented Oct 9, 2015 at 12:04

Markus Weninger · Accepted Answer · 2017-09-01 07:02:07Z

62

Even though the accepted answer should work, you can achieve it in a much easier way.

Just run gradle run --debug-jvm. This starts the application in remote debug mode, and you can attach with any remote debugger, e.g., Eclipse, on port 5005.
Assuming you use Eclipse as IDE: In Eclipse, go on your Project -> Debug as... -> Debug Configuration -> Remote Java Application. As host set localhost, as port 5005, and you are free to go.

For more information see the official Gradle Java plugin doc regarding testing.

[...] can also be enabled at invocation time via the --debug-jvm task option (since Gradle 1.12).

edited Sep 1, 2017 at 7:02

answered Aug 15, 2017 at 7:53

Markus Weninger

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6 Comments

Gaurava Agarwal Over a year ago

this works, but not the accepted answer. The gradle one is the one actually works.

Vincent Gerris Over a year ago

this works indeed. to change the default port, in the build.gradle file test section add like this: test { jvmArgs=["-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5099"] }

Luke Hutchison Over a year ago

Is there a commandline switch to make this suspend when Eclipse connects, which doesn't require changing jvmArgs in build.gradle?

robothy Over a year ago

Here is the Gradle official guide. docs.gradle.org/current/userguide/…

Nick Sabia Over a year ago

If you have gradle in your project as a wrapper (and you likely don't have gradle installed by itself on your system) and you're using Eclipse: 1) Locate the gradlew file in your project 2) Open up a new terminal in Eclipse by going into the package explorer and right clicking the project containing gradlew > Show in Local Terminal > Terminal 3) Within the newly created terminal, enter gradlew run --debug-jvm 4) Perform step 2 in the answer above.

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Markus Weninger · Accepted Answer · 2019-01-28 08:33:27Z

33

To debug a Gradle project in Eclipse follow these steps:

Step 1:
Put these in the build.gradle file:

tasks.withType(JavaExec) {
    if (System.getProperty('DEBUG', 'false') == 'true') {
        jvmArgs '-Xdebug', '-Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=9099'
    }
}

Step 2:

From the root of your project run:

gradle -DDEBUG=true run

You will now see something like this in the console:

Listening for transport dt_socket at address: 9099

Step 3:

Now set breakpoints in Eclipse in your source files.

Step 4:

As last step, now right-click in Eclipse on Project > Debug as > Debug configuration > Remote Java application.

There you have to set these fields:

1. Project (this should be set to name of your Eclipse project)
2. Host (here it's localhost)
3. Port (in this example it will be 9099)

Click "Debug". Now your program will stop whenever it hits a breakpoint in Eclipse.

To see details of these steps with an example project see this gradle example on GitHub:

edited Jan 28, 2019 at 8:33

Markus Weninger

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answered Oct 24, 2016 at 23:24

Ayon Nahiyan

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5 Comments

themathmagician Over a year ago

Hey, when I try your steps, setting the debug configuration for remote application results in the error message Failed to connect to remote VM. Connection refused. I am trying to run a task that executes my cucumber tests from gradle, and stop at a breakpoint in the Java code. Any tips?

Ayon Nahiyan Over a year ago

Hey @themathmagician, Im havent used cucumber tests but if its some kind of unit test you need to change the gradle function a little.Follow this example for unit tests: github.com/ayonious/gradle-tutorial/tree/master/…

Jerinaw Over a year ago

This worked for me but I needed to change debug_socket to dt_socket. jvmArgs '-Xdebug', '-Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=9099'

Ayon Nahiyan Over a year ago

@Jerinaw thanks for mentioning it updating my answer

Levijatanu Over a year ago

Xrunjdwp is for Java 1.4 or less

Jad Gh · Accepted Answer · 2019-04-19 09:21:22Z

I wasn't able to run the gradle task in debug mode through adding the following code in build.gradle file.

tasks.withType(JavaExec) {
    if (System.getProperty('DEBUG', 'false') == 'true') {
        jvmArgs '-Xdebug', '-Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=5005'
    }
}

Instead I did the following steps and managed to run it automatically in debug mode :

All you need to to do is to go to $GRADLE_HOME/bin.
Edit the file gradle or gradle.bat depending on your OS.
Set the JVM parameter in the OS-specific way. For example:

gradle(UNIX) case :

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

gradle.bat(NT) case :

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

. 4. Run the Gradle command from the console.

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