action to build and publish javadoc to pages (langchain4j#504)

Adds the following:

 * add maven plugin for generating javadoc 
 * action to build and publish javadoc to pages
 * update javadoc link in docusaurus

.github/workflows/javadoc.yaml

@@ -0,0 +1,48 @@
+name: Deploy Javadoc
+# in folder apidocs/
+
+on:
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
+# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  build-and-deploy:
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Check Out Source Code
+        uses: actions/checkout@v2
+
+      - name: Set up JDK 8
+        uses: actions/setup-java@v2
+        with:
+          java-version: '8'
+          distribution: 'adopt'
+
+      - name: Generate Javadoc
+        run: mvn javadoc:aggregate -DskipTests -pl '!langchain4j-opensearch,!code-execution-engines/langchain4j-code-execution-engine-graalvm-polyglot,!langchain4j-neo4j'
+
+      - name: Setup Pages
+        uses: actions/configure-pages@v3
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v2
+        with:
+          # Upload site folder
+          path: './target/site/.'
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v2

docs/docusaurus.config.js

@@ -86,7 +86,7 @@ const config = {
                     },
                     {to: '/docs/tutorials', label: 'Tutorials', position: 'left'},
                     {to: '/docs/category/integrations', label: 'Integrations', position: 'left'},
-                    {to: 'https://langchain4j.dev/javadoc/', label: 'Javadoc', position: 'left'},
+                    {to: 'https://lizeraes.github.io/langchain4j/apidocs/', label: 'Javadoc', position: 'left'},
                     {to: '/blog', label: 'Blog', position: 'left'},
                     {
                         href: 'https://github.com/langchain4j/langchain4j',

pom.xml

@@ -57,4 +57,55 @@
 
     </modules>
 
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <version>3.5.0</version>
+                <executions>
+                    <execution>
+                        <id>attach-javadocs</id>
+                        <goals>
+                            <goal>jar</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>aggregate</id>
+                        <goals>
+                            <goal>aggregate</goal>
+                        </goals>
+                        <phase>site</phase>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <reporting>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <version>3.5.0</version>
+                <reportSets>
+                    <reportSet>
+                        <id>aggregate</id>
+                        <inherited>false</inherited>
+                        <reports>
+                            <report>aggregate</report>
+                        </reports>
+                    </reportSet>
+                    <reportSet>
+                        <id>default</id>
+                        <reports>
+                            <report>javadoc</report>
+                        </reports>
+                    </reportSet>
+                </reportSets>
+            </plugin>
+        </plugins>
+    </reporting>
+
+
 </project>