Category: Spring

Java Time with Introspective GraphQL on Chaos Database AKA Pre- Refactor Prototype Mutating Database Spring Boot Java Hack App

With the previous work to get a testing environment built and running done (in Python), I was ready to get started on the GraphQL API as previously described. As a refresher, this description,

singular mission to build a GraphQL API against a Mongo database where the idea is, one could query the underlying collections, documents, and fields with the assumption that users would be adding or possibly removing said collections, documents, and fields as they needed.

My intent is to build with with a Java + Spring stack. Just like with the Python app in the previous post, the first thing I like to do is just get the baseline GraphQL API “Hello World” app up and running.

At the end of this post I’ll include/link the Github repository.

Phase 1: Getting the Initial GraphQL API Compiling & Running with a “Hello World”.

Prerequisites & Setup

  • The post previous to this “Fruit and Snakes: Frequent Mutative Mongo User Database with Python” I created the Mongo Database and setup the app that would create, every few seconds, new collections, documents, and other collateral to put into a Mongo database for the sole purpose of creating this GraphQL API.
  • I’ll be using Java 17 for this work, so to ensure the least risk of versioning issues, get Java 17. The same goes for Spring 3. I’ve shown my selections from the Spring Initializr (not using Intellij? Cool, get a start with the Spring Initializr Site) in the screenshots that follow.
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Gradle Build Tool

A few helpful links and details to where information is on the Gradle Build Tool.

Installation

Via SDKMAN sdk install gradle x.y.z where x.y.z is the version, like 8.0.2.

Via Brew with brew install gradle.

Manually check out the instructions here.

Building a Java Library (or application, Gradle plugin, etc)

Using the init task. From inside a directory with the pertinent project.

gradle init

You’ll be prompted for options.

With the project initialized this is what that initialized folder structure looks like.

At this point add the Java code for the library, similar to this example, and execute a build like this.

./gradlew build

Build Collateral

View the test report via the HTML output file at lib/build/reports/tests/test/index.html.

The JAR file is available in lib/build/libs with the name lib.jar. Verify the archive is valid with jar tf lib/build/libs/lib.jar.

Add the version by setting the version = '0.1.1' in the build.gradle file.

Run the jar task ./gradlew jar and the build will create a lib/build/libs/lib-0.1.1.jar with the expected version.

Add all this to the build by adding the following to the build.gradle file:

tasks.named('jar') {
    manifest {
        attributes('Implementation-Title': project.name,
                   'Implementation-Version': project.version)
    }
}

Verifying this all works, execute a ./gradlew jar and then extract the MANIFEST.MF via jar xf lib/build/libs/lib-0.1.0.jar META-INF/MANIFEST.MF.

Adding API Docs

In the */Library.java file, replace the / in the comment by / * so that we get javadoc markup.

Run the ./gradlew javadoc task. The generated javadoc files are located at lib/build/docs/javadoc/index.html.

To add this as a build task, in build.gradle add a section with the following:

java {
    withJavadocJar()
}

Publish a Build Scan

Execute a build scan with ./gradlew build --scan.

Common Issues + Tips n’ Tricks

gradlew – Permission Denied issue

Let’s say you execute Gradle with ./gradlew with whatever parameter and immediately get a response of “Permission Denied”. The most common solution, especially for included gradlew executables included in repositories, is to just give the executable permission to execute. This is done with a simple addition chmod +x gradelw and you should now be ready to execute!