Building a REST API with Java and Vert.x Framework

PostgreSQL Integration

This guide will walk you through creating a REST API using Java and the Vert.x framework, connecting to a PostgreSQL database. The API will have two endpoints:

• GET /api/getUserData: Retrieves user data from the users table based on the provided user_id parameter.
• POST /api/updateUser: Updates user data in the users table based on the provided user_id, fullname, and email parameters.

Prerequisites:

• Java 11 or higher
• Basic understanding of Java programming
• Familiarity with REST API concepts
• PostgreSQL database set up

Steps:

1. Create a Vert.x project: Use the vertx-quickstart tool to create a basic Vert.x project:

   vertx-quickstart --lang java --name my-api

2. Add dependencies: Add the following dependencies to your project’s pom.xml file:

   <dependency>
       <groupId>io.vertx</groupId>
       <artifactId>vertx-web</artifactId>
       <version>${vertx.version}</version>
   </dependency>
   <dependency>
       <groupId>io.vertx</groupId>
       <artifactId>vertx-pg-client</artifactId>
       <version>${vertx.version}</version>
   </dependency>

3. Define data models: Create a models.java file to define the data structures for users:

   public class User {
       private int userId;
       private String fullname;
       private String email;

       // Getters and setters omitted for brevity
   }

4. Implement database access: Create a db.java file for database operations:

   import io.vertx.core.Future;
   import io.vertx.pgclient.PgClient;
   import io.vertx.pgclient.pool.Pool;
   import java.util.Optional;

   public class Database {

       private final Pool pool;

       public Database(Pool pool) {
           this.pool = pool;
       }

       public Future<Optional<User>> getUserData(int userId) {
           return pool.query("SELECT * FROM users WHERE user_id = $1", new Integer[]{userId})
                   .execute()
                   .flatMap(rows -> {
                       if (rows.rowCount() == 1) {
                           return Future.succeededFuture(new User(
                                   rows.iterator().next().getInt("user_id"),
                                   rows.iterator().next().getString("fullname"),
                                   rows.iterator().next().getString("email")
                           ));
                       } else {
                           return Future.failedFuture(new RuntimeException("User not found"));
                       }
                   });
       }

       public Future<Void> updateUser(User user) {
           return pool.query("UPDATE users SET fullname = $1, email = $2 WHERE user_id = $3",
                   new String[]{user.getFullname(), user.getEmail(), String.valueOf(user.getUserId())})
                   .execute()
                   .flatMap(rows -> {
                       if (rows.rowCount() == 1) {
                           return Future.succeededFuture();
                       } else {
                           return Future.failedFuture(new RuntimeException("User not found"));
                       }
                   });
       }
   }

5. Create route handlers: Create a routes.java file to define the API routes and handlers: “`java
   import io.vertx.core.Future;
   import io.vertx.core.http.HttpServerResponse;
   import io.vertx.ext.web.Router;
   import io.vertx.ext.web.RoutingContext;
   import io.vertx.pgclient.pool.Pool;
   import java.util.logging.Logger; public class Routes { private static final Logger LOGGER = Logger.getLogger(Routes.class.getName()); private final Router router;
   private final Database database; public Routes(Router router, Database database) {
   this.router = router;
   this.database = database;
   } public void registerRoutes() {
   router.get(“/api/getUserData/:userId”, this::getUserDataHandler);
   router.post(“/api/updateUser”, this::updateUserHandler);
   } private void getUserDataHandler(RoutingContext context) {
   int userId = Integer

MySQL Integration

This guide will walk you through creating a REST API using Java and the Vert.x framework, connecting to a MySQL database. The API will have two endpoints:

• GET /api/getUserData: Retrieves user data from the users table based on the provided user_id parameter.
• POST /api/updateUser: Updates user data in the users table based on the provided user_id, fullname, and email parameters.

Prerequisites:

• Java 11 or higher
• Basic understanding of Java programming
• Familiarity with REST API concepts
• MySQL database set up

Steps:

1. Create a Vert.x project: Use the vertx-quickstart tool to create a basic Vert.x project:

   vertx-quickstart --lang java --name my-api

2. Add dependencies: Add the following dependencies to your project’s pom.xml file:

   <dependency>
       <groupId>io.vertx</groupId>
       <artifactId>vertx-web</artifactId>
       <version>${vertx.version}</version>
   </dependency>
   <dependency>
       <groupId>io.vertx</groupId>
       <artifactId>vertx-mysql-client</artifactId>
       <version>${vertx.version}</version>
   </dependency>

3. Define data models: Create a models.java file to define the data structures for users:

   public class User {
       private int userId;
       private String fullname;
       private String email;

       // Getters and setters omitted for brevity
   }

4. Implement database access: Create a db.java file for database operations:

   import io.vertx.core.Future;
   import io.vertx.mysql.client.MySQLConnectOptions;
   import io.vertx.mysql.client.MySQLConnection;
   import io.vertx.mysql.client.Pool;
   import java.util.Optional;

   public class Database {

       private final Pool pool;

       public Database(Pool pool) {
           this.pool = pool;
       }

       public Future<Optional<User>> getUserData(int userId) {
           return pool.query("SELECT * FROM users WHERE user_id = ?", new Integer[]{userId})
                   .execute()
                   .flatMap(rows -> {
                       if (rows.result().size() == 1) {
                           return Future.succeededFuture(new User(
                                   rows.result().get(0).getInteger("user_id"),
                                   rows.result().get(0).getString("fullname"),
                                   rows.result().get(0).getString("email")
                           ));
                       } else {
                           return Future.failedFuture(new RuntimeException("User not found"));
                       }
                   });
       }

       public Future<Void> updateUser(User user) {
           return pool.query("UPDATE users SET fullname = ?, email = ? WHERE user_id = ?",
                   new String[]{user.getFullname(), user.getEmail(), String.valueOf(user.getUserId())})
                   .execute()
                   .flatMap(rows -> {
                       if (rows.result().size() == 1) {
                           return Future.succeededFuture();
                       } else {
                           return Future.failedFuture(new RuntimeException("User not found"));
                       }
                   });
       }
   }

5. Create route handlers: Create a routes.java file to define the API routes and handlers: “`java
   import io.vertx.core.Future;
   import io.vertx.core.http.HttpServerResponse;
   import io.vertx.ext.web.Router;
   import io.vertx.ext.web.RoutingContext;
   import io.vertx.mysql.client.Pool;
   import java.util.logging.Logger; public class Routes { private static final Logger LOGGER = Logger.getLogger(Routes.class.getName()); private final Router router;
   private final Database database; public Routes(Router router, Database database) {
   this.router = router;
   this.database = database;
   } public void registerRoutes() {
   router.get(“/api/getUserData/:userId”, this::getUserDataHandler);
   router.post(“/api/updateUser”, this::updateUserHandler);
   }