add spring boot hello world code

.gitignore

@@ -4,20 +4,14 @@
 # Log file
 *.log
 
-# BlueJ files
-*.ctxt
-
-# Mobile Tools for Java (J2ME)
-.mtj.tmp/
-
-# Package Files #
+# Package Files
 *.jar
-*.war
-*.nar
-*.ear
 *.zip
 *.tar.gz
 *.rar
 
-# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
-hs_err_pid*
+# Generated Sources
+target
+
+# IDE Files
+.idea

README.md

@@ -1,2 +1,51 @@
-# spring-boot-hello-world
-A simple Spring Boot app to send hello world message to a user
+# Spring Boot Hello World
+
+**A simple Spring Boot app to send hello world message to a user**
+
+## How to Run Application
+
+**Start the application using any of the commands mentioned below**
+
+> **Note:** First two commands need to run inside the root folder of this project i.e inside the **spring-boot-hello-world** folder
+
+
+- **Using maven** <br/>``` mvn spring-boot:run```
+
+
+- **From jar file**
+  Create a jar file using '**mvn clean install**' command and then execute
+  <br/>```java -jar target/hello-world-1.0.1-SNAPSHOT.jar```
+
+
+- **Directly from IDE**
+  <br/>```Right click on HelloWorldApplication.java and click on 'Run' option```
+  <br/><br/>
+
+> **Note:** By default spring boot application starts on port number 8080. If port 8080 is occupied in your system then you can change the port number by uncommenting and updating the **server.port** property inside the **application.properties** file that is available inside the **src > main > resources** folder.
+
+<br/>
+
+**Send an HTTP GET request to '/hello' endpoint using any of the two methods**
+
+- **Browser or REST client**
+  <br/>```http://localhost:8080/hello```
+
+
+- **cURL**
+  <br/>```curl --request GET 'http://localhost:8080/hello'```
+
+
+## How to Run Unit Test Cases
+
+**Run the test cases using any of the commands mentioned below**
+
+> **Note:** These commands need to run inside the root folder of this project i.e inside the **spring-boot-hello-world** folder
+
+- **To run all the test cases**
+  <br/>```mvn test```
+
+
+- **To run a particular test class**
+  <br/>```mvn -Dtest=HelloWorldControllerTest test```
+  <br/>or
+  <br/>```mvn -Dtest=HelloWorldApplicationTests test```

pom.xml

@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.4.5</version>
+    </parent>
+
+    <groupId>com.example</groupId>
+    <artifactId>hello-world</artifactId>
+    <version>1.0.1-SNAPSHOT</version>
+
+    <name>hello-world</name>
+    <description>A simple Spring Boot app to send hello world message to a user</description>
+
+    <properties>
+        <java.version>1.8</java.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

src/main/java/com/example/helloworld/HelloWorldApplication.java

@@ -0,0 +1,13 @@
+package com.example.helloworld;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class HelloWorldApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(HelloWorldApplication.class, args);
+    }
+
+}

src/main/java/com/example/helloworld/controller/HelloWorldController.java

@@ -0,0 +1,13 @@
+package com.example.helloworld.controller;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class HelloWorldController {
+
+    @GetMapping("/hello")
+    public String sendGreetings() {
+        return "Hello, World!";
+    }
+}

src/main/resources/application.properties

@@ -0,0 +1,2 @@
+# configuring port number on which application should run
+#server.port=8081

src/test/java/com/example/helloworld/HelloWorldApplicationTests.java

@@ -0,0 +1,23 @@
+package com.example.helloworld;
+
+import com.example.helloworld.controller.HelloWorldController;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+
+@SpringBootTest
+class HelloWorldApplicationTests {
+
+    @Autowired
+    private HelloWorldController helloWorldController;
+
+    @Test
+    void contextLoads() {
+        // to ensure that controller is getting created inside the application context
+        assertNotNull(helloWorldController);
+    }
+
+}

src/test/java/com/example/helloworld/controller/HelloWorldControllerTest.java

@@ -0,0 +1,27 @@
+package com.example.helloworld.controller;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@SpringBootTest
+@AutoConfigureMockMvc
+public class HelloWorldControllerTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Test
+    public void shouldReturnExpectedMessage() throws Exception {
+
+        mockMvc.perform(get("/hello"))
+                .andExpect(status().isOk())
+                .andExpect(content().string("Hello, World!"));
+    }
+}