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+categories = ["software"]
+tags = ["java"]
+date = 2024-11-10T15:55:42Z
+description = ""
+draft = false
+slug = "java-spring-tomcat"
+title = "☕ Developing Spring REST API - Pt. I"
+author = "nicholas"
+++
+
+Much time has passed since I last worked with Spring framework in Java. I need to build out a development environment to enable me to build Java applications. In this log, the environment will be configured to include the following tools and features:
+   * Eclipse IDE
+   * Java (JRE, JDK)
+   * Maven (dependency manager, etc.)
+   * Spring Boot (Java framework)
+
+This log is a series of baby steps that will result in basic implementation of a REST API.
+
+
+## Code Editor
+First, I need a code editor/IDE. I selected Eclipse for no particular reason. My understanding is that IntelliJ IDEA is a more modern, refined alternative that I may try down the line. For now, all I need is a default installation to get started.
+
+
+## Hello World
+I allow the IDE to walk me through a hello world tutorial to become familiar with the software and remind myself of the basic structure of a Java program.
+
+
+## Spring REST API endpoint
+My next milestone is to set up a trivial API endpoint to familiarize myself with Spring MVC. I will use this framework to build an endpoint that will return "hello world". Eventually, this project will become an API for a plant simulation app.
+
+ * I use spring initializr to automate the creation of the necessary boilerplate to run a minimally viable endpoint.
+
+ * I create a controller class for the API: PlantController.java.
+ * This class uses Spring's @RestController and @GetMapping annotations to define the controller and one endpoint.
+ * For now, I have defined a GET endpoint at /helloworld, which returns the string "hello world".
+
+```java
+package plantsim.PlantSimulatorAPI;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class PlantController {
+
+	@GetMapping("/helloworld")
+	public String helloworld() {
+		return "hello world";
+	}
+
+}
+```
+It works. Now I can configure my data models and database.
+
+## Database
+Database configuration will require a few steps.
+
+* Create in-memory database with h2
+* Using the credentials defined below and in application.properties I am able to connect to the database testdb at /h2-console.
+
+```java
+spring.datasource.url=jdbc:h2:mem:testdb
+spring.datasource.driver-class-name=org.h2.Driver
+spring.datasource.username=sa
+spring.datasource.password=password
+spring.h2.console.enabled=true
+```
+
+ * In the h2 console, I can execute SQL queries and explore the database structure, etc.
+
+ 1. Initialize database – populate with data
+
+ * Since I have defined an entity class for the plant object, Hibernate will automatically create the plant database table for me. I will need to populate the table data, however.
+ * I populate the tale with data using data.sql. By default, Spring Boot will look in src/main/resources for the script and execute it after the table has been initialized (according to application.properties -> spring.jpa.defer-datasource-initialization=true
+ * I configure the script below to insert a couple of rows:
+
+```sql
+-- Insert rows
+INSERT INTO plant (name) VALUES ('Ficus Audrey');
+INSERT INTO plant (name) VALUES ('Lucky Bamboo');
+INSERT INTO plant (name) VALUES ('Chinese Money Plant');   
+```
+ 3. Configure API endpoint to return plant objects
+
+ * To return a plant object instead of a string, I will need to configure following:
+   * Plant entity that matches database schema – This will use object-relational mapping (ORM) to map my Java entities to my database table plant
+
+```java
+package plantsim.PlantSimulatorAPI;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+
+@Entity
+public class Plant {
+
+	@Id
+	@GeneratedValue(strategy = GenerationType.IDENTITY)
+	private Long id;
+	private String name;
+
+	public Plant() {
+	}
+
+	public Plant(Long id, String name) {
+		this.id = id;
+	}
+
+	public void setId(Long id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+}
+```  
+ * Add JPA dependency to pom.xml – JPersistence API
+```
+jakarta.persistence
+jakarta.persistence-api
+3.1.0
+```
+ * Create a JPA repository to fetch the Plant objects from testdb.
+
+
+
+
+```java
+package plantsim.PlantSimulatorAPI;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface PlantRepository extends JpaRepository {
+}
+```
+
+ * Update the controller to return the Plant object.
+
+
+
+
+```java
+    @Autowired
+	private PlantRepository plantRepository;
+
+	@GetMapping("/plant")
+	public List getPlants() {
+		return plantRepository.findAll();
+	}
+```
+
+## Results
+
+If I navigate to /plant, the program returns a JSON-formatted string of the all of the plants stored in the database. I will use this as a foundation to later build into the project actual functionality.
+
+```json
+ [
+  {
+    "name": "Ficus Audrey"
+  },
+  {
+    "name": "Lucky Bamboo"
+  },
+  {
+    "name": "Chinese Money Plant"
+  }
+]
+```
+
+