Creating resources

To create basic Spring project resources, you can use Spring Initializr (https://start.spring.io/) . In Spring Initializr, provide the necessary details:

Generate a Maven Project with Java and Spring Boot 1.5.9.

Group: com.packtpub.restapp

Artifact: ticket-management

Search for dependencies:  Select Web (Full Stack Web Development with Tomcat and Web MVC)  dependency 

After filling in the details, just click Generate Project; then it will create Spring basic resources in ZIP format. We can start using the project by importing them into Eclipse. 

The Spring 5 POM file will look like this:

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.packtpub.restapp</groupId>
  <artifactId>ticket-management</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>
  <name>ticket-management</name>
  <description>Demo project for Spring Boot</description>
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.9.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  </properties>
  <dependencies>
    <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>

Let's remove the parent to simplify the POM:

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.9.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>

As we removed the parent, we may need to add the version in all of our dependencies. Let's add the version in our dependencies:

<dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
      <version>1.5.9.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
      <version>1.5.9.RELEASE</version>
    </dependency>
  </dependencies>

As the dependency artifact spring-boot-starter-web version 1.5.9 is based on Spring 4.3.11, we will have to upgrade to Spring 5. Let's clean and upgrade our POM file to bring in Spring 5 updates:

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.packtpub.restapp</groupId>
  <artifactId>ticket-management</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>
  <name>ticket-management</name>
  <description>Demo project for Spring Boot</description> 
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
      <version>1.5.9.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
      <version>1.5.9.RELEASE</version>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>

You can see Spring 5-related dependencies in the preceding POM file. Let's test them with the REST endpoint. First, create a Spring Boot main file to initialize Spring Boot:

@SpringBootApplication
public class TicketManagementApplication {  
  public static void main(String[] args) {
    SpringApplication.run(TicketManagementApplication.class, args);
  }
}

You can start running the Spring Boot on Eclipse by right-clicking the project and selecting Run As | Spring Boot App. If you do this, you will see logs in the Eclipse console.

The following is a sample log. You may not see an exact match; however, you will get an idea of how the server running log will look:

  . ____ _ __ _ _
 /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/ ___)| |_)| | | | | || (_| | ) ) ) )
  ' |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot :: (v1.5.7.RELEASE)

2017-11-05 15:49:21.380 INFO 8668 --- [ main] c.p.restapp.TicketManagementApplication : Starting TicketManagementApplication on DESKTOP-6JP2FNB with PID 8668 (C:\d\spring-book-sts-space\ticket-management\target\classes started by infoadmin in C:\d\spring-book-sts-space\ticket-management)
2017-11-05 15:49:21.382 INFO 8668 --- [ main] c.p.restapp.TicketManagementApplication : No active profile set, falling back to default profiles: default
2017-11-05 15:49:21.421 INFO 8668 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@5ea434c8: startup date [Sun Nov 05 15:49:21 EST 2017]; root of context hierarchy
2017-11-05 15:49:22.205 INFO 8668 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2017-11-05 15:49:22.213 INFO 8668 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
...
..

...
...
2017-11-05 15:49:22.834 INFO 8668 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
2017-11-05 15:49:22.881 INFO 8668 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)

You should see Tomcat started on port(s): 8080 in the last lines of the log.

When you check the URI http://localhost:8080, you will see the following error:

Whitelabel Error Page

This application has no explicit mapping for /error, so you are seeing this as a fallback.

Sun Nov {current date}
There was an unexpected error (type=Not Found, status=404).
No message available

The preceding error is saying that there is no corresponding URI configured in the application. Let's fix this issue by creating a controller called HomeController under the com.packtpub.restapp package:

package com.packtpub.restapp;
import java.util.LinkedHashMap;
import java.util.Map;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/")
public class HomeController {
  @ResponseBody
  @RequestMapping("")
  public Map<String, Object> test(){
    Map<String, Object> map = new LinkedHashMap<>();
    map.put("result", "Aloha");    
    return map;
  }
}

In the preceding code, we created a dummy controller called HomeController with a simple map as a result. Also, we added the new controller we need to have these classes autoscanned by our main application, in our case the TicketManagementApplication class. We will tell them by adding @ComponentScan("com.packtpub") in the main class. Finally, our main class will look like the following:

package com.packtpub.restapp.ticketmanagement;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
@ComponentScan("com.packtpub")
@SpringBootApplication
public class TicketManagementApplication {
  public static void main(String[] args) {
    SpringApplication.run(TicketManagementApplication.class, args);
  }
}

When you restart the Spring Boot App, you will see the REST endpoint working (localhost:8080):

{
  result: "Aloha"
}