Base DependencyInjection setup

app/build.gradle

@@ -42,8 +42,11 @@ dependencies {
   implementation "org.jooq:jooq-codegen:$jooqVersion"
   runtimeOnly "org.postgresql:postgresql:$postgresVersion"
   jooqGenerator "org.postgresql:postgresql:$postgresVersion"
+  implementation 'com.zaxxer:HikariCP:5.0.1' // Connection pooling for postgres/jdbc
 
   implementation "com.google.inject:guice:$guiceVersion"
+  implementation('org.glassfish.jersey.inject:jersey-hk2:3.1.0')
+  implementation "org.glassfish.hk2:guice-bridge:3.0.3"
 
   compileOnly 'org.projectlombok:lombok:1.18.24'
   annotationProcessor 'org.projectlombok:lombok:1.18.24'

app/src/main/java/org/vss/VSSApplication.java

@@ -1,10 +1,31 @@
 package org.vss;
 
+import com.google.inject.Guice;
+import com.google.inject.Injector;
+import jakarta.inject.Inject;
 import jakarta.ws.rs.ApplicationPath;
+import org.glassfish.hk2.api.ServiceLocator;
 import org.glassfish.jersey.server.ResourceConfig;
+import org.jvnet.hk2.guice.bridge.api.GuiceBridge;
+import org.jvnet.hk2.guice.bridge.api.GuiceIntoHK2Bridge;
+import org.vss.guice.BaseModule;
 
 @ApplicationPath("/")
 public class VSSApplication extends ResourceConfig {
-  public VSSApplication() {
+
+  @Inject
+  public VSSApplication(ServiceLocator serviceLocator) {
+    packages("org.vss");
+    Injector injector = Guice.createInjector(new BaseModule());
+    initGuiceIntoHK2Bridge(serviceLocator, injector);
+  }
+
+  // By default, Jersey framework uses HK2 for dependency injection.
+  // To use Guice as our dependency injection framework, we provide guice injector to hk2-bridge.
+  // So that hk2 can query guice injector for creating/injecting objects.
+  private void initGuiceIntoHK2Bridge(ServiceLocator serviceLocator, Injector injector) {
+    GuiceBridge.getGuiceBridge().initializeGuiceBridge(serviceLocator);
+    GuiceIntoHK2Bridge guiceBridge = serviceLocator.getService(GuiceIntoHK2Bridge.class);
+    guiceBridge.bridgeGuiceInjector(injector);
   }
 }

app/src/main/java/org/vss/guice/BaseModule.java

@@ -0,0 +1,83 @@
+package org.vss.guice;
+
+import com.google.inject.AbstractModule;
+import com.google.inject.Provides;
+import com.google.inject.Singleton;
+import com.zaxxer.hikari.HikariConfig;
+import com.zaxxer.hikari.HikariDataSource;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Properties;
+import org.jooq.DSLContext;
+import org.jooq.SQLDialect;
+import org.jooq.impl.DSL;
+import org.vss.KVStore;
+import org.vss.impl.postgres.PostgresBackendImpl;
+
+public class BaseModule extends AbstractModule {
+
+  @Override
+  protected void configure() {
+    // Provide PostgresBackend as default implementation for KVStore.
+    bind(KVStore.class).to(PostgresBackendImpl.class).in(Singleton.class);
+  }
+
+  @Provides
+  @Singleton
+  // Provide DSLContext which is to be used by PostgresBackend
+  public DSLContext provideDSLContext() throws ClassNotFoundException {
+    // Required to load postgres drivers in tomcat
+    Class.forName("org.postgresql.Driver");
+    return DSL.using(HikariCPDataSource.dataSource, SQLDialect.POSTGRES);
+  }
+}
+
+// Provide Hikari Connection Pooling configuration for jdbc connection management.
+// Hikari is high-performance connection pooling library which will maintain a set of connections
+// to the database for us.
+// When we provide `HikariCPDataSource` to DSLContext, jOOQ will internally `acquire` and `release`
+// connections from pool.
+// For HikariCP config, we provide some sane defaults, but they are meant to be changed and tuned.
+// For specific parameter functionality, refer to HikariCP docs.
+class HikariCPDataSource {
+
+  private static HikariConfig config = new HikariConfig();
+  public static HikariDataSource dataSource;
+
+  static {
+    try (InputStream input = HikariCPDataSource.class.getClassLoader()
+        .getResourceAsStream("hikariJdbc.properties")) {
+      Properties hikariJdbcProperties = new Properties();
+      hikariJdbcProperties.load(input);
+
+      config.setJdbcUrl(hikariJdbcProperties.getProperty("jdbc.url"));
+      config.setUsername(hikariJdbcProperties.getProperty("jdbc.username"));
+      config.setPassword(hikariJdbcProperties.getProperty("jdbc.password"));
+
+      config.setMaximumPoolSize(
+          Integer.parseInt(hikariJdbcProperties.getProperty("hikaricp.maxPoolSize")));
+      config.setMinimumIdle(
+          Integer.parseInt(hikariJdbcProperties.getProperty("hikaricp.minimumIdle")));
+      config.setConnectionTimeout(
+          Long.parseLong(hikariJdbcProperties.getProperty("hikaricp.connectionTimeout")));
+      config.setIdleTimeout(
+          Long.parseLong(hikariJdbcProperties.getProperty("hikaricp.idleTimeout")));
+      config.setMaxLifetime(
+          Long.parseLong(hikariJdbcProperties.getProperty("hikaricp.maxLifetime")));
+
+      config.addDataSourceProperty("cachePrepStmts",
+          hikariJdbcProperties.getProperty("hikaricp.cachePrepStmts"));
+      config.addDataSourceProperty("prepStmtCacheSize",
+          hikariJdbcProperties.getProperty("hikaricp.prepStmtCacheSize"));
+      config.addDataSourceProperty("prepStmtCacheSqlLimit",
+          hikariJdbcProperties.getProperty("hikaricp.prepStmtCacheSqlLimit"));
+
+      dataSource = new HikariDataSource(config);
+    } catch (IOException e) {
+      throw new RuntimeException("Unable to read hikariJdbcProperties from resources");
+    }
+  }
+
+  private HikariCPDataSource() {
+  }
+}

app/src/main/resources/hikariJdbc.properties

@@ -0,0 +1,23 @@
+# Default properties, these are meant to be changed according to application needs.
+
+jdbc.url=jdbc:postgresql://localhost:5432/postgres
+jdbc.username=postgres
+jdbc.password=
+
+# Idle Timeout
+hikaricp.minimumIdle=10
+
+# Set connectionTimeout to 30 secs
+hikaricp.connectionTimeout=30000
+
+# Set idle timeout to 10 minutes
+hikaricp.idleTimeout=600000
+
+# Set Maximum lifetime of a connection to 30minutes
+hikaricp.maxLifetime=1800000
+
+# Performance Optimizations
+hikaricp.maxPoolSize=50
+hikaricp.cachePrepStmts=true
+hikaricp.prepStmtCacheSize=250
+hikaricp.prepStmtCacheSqlLimit=2048