[JAVA] Let's make a simple API with EC2 + RDS + Spring boot ①

Overview

This is the procedure to deploy the spring boot project on the EC2 instance and create a very simple API. In ①, first deploy the project on EC2 and create an API that returns POJO.

Goal of this article

First, build a very simple REST API that returns POJOs on your EC2 instance. It will be the next time to connect to MySQL and get the data.

Target person

This article does not explain spring boot or AWS in detail. Therefore, for those who want to try AWS using spring for the time being.

This article is based on the following environment and knowledge.

• AWS account
• Java runtime environment
• maven environment
• SSH
• (Free version is fine, so it is desirable to have intelliJ)

environment

• JDK1.8
• Java8
• spring boot 2.1.1

1. Create spring boot project ~ REST API construction

Project creation

First, generate a template for the spring boot project with Spring initializr. As the name suggests, spring initializr makes it easy to create a template for a spring boot project. In addition to being able to specify the version, it is very convenient because you can create a template with the specified library etc. included.

Let's leave Group and Artifact as they are. The important thing is Dependencies. Let's add the following to Dependencies.

• Web
• JPA
• Lombok
• MySQL

When added, it will be as follows.

Press Generate Priject to download the project.

API construction

Unzip the project you downloaded earlier and open it in an IDE. This article uses intelliJ.

First, comment out the JPA and MySQL libraries in pom.xml. I will not use it in this article, but I will use it from the next time. Also, if you do not comment out here, it will cause an error later.

pom.xml

...
       <dependencies>
		<!--<dependency>-->
			<!--<groupId>org.springframework.boot</groupId>-->
			<!--<artifactId>spring-boot-starter-data-jpa</artifactId>-->
		<!--</dependency>-->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<!--<dependency>-->
			<!--<groupId>mysql</groupId>-->
			<!--<artifactId>mysql-connector-java</artifactId>-->
			<!--<scope>runtime</scope>-->
		<!--</dependency>-->
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>
...

** Let's make the package structure under main as follows **

main └ java 　 ┗ com.example.demo 　　　　┣ controller 　　　　　　　└　PersonController.java 　　　　┣ service 　　　　　　　└　PersonService.java 　　　　┣ model 　　　　　　　└　Person.java 　　　　└ DemoApplication.java

It's okay if it looks like the following in intelliJ.

** Then rewrite each file as follows **

Person.java

@Builder
@AllArgsConstructor
@NoArgsConstructor
@ToString
@Data
public class Person {
    private String name;
    private Integer age;
    private String gender;
}

PersonService.java

@Service
public class PersonService {
    public Person getPerson(){
        return new Person().builder()
            .name("hoge")
            .age(16)
            .gender("man")
            .build();
    }
}

PersonController.java

@RestController
@RequiredArgsConstructor
public class PersonController {
    private final PersonService personService;

    @RequestMapping(path= "person", method = RequestMethod.GET)
    public Person getPerson(){
        return personService.getPerson();
    }
}

• Since ʻimpoet statement` is omitted for each, please describe the necessary import statement as appropriate. *

** Let's do it **

If you access http: // localhost: 8080 / person and get the following response, it's okay.

Package

Package the project created this time for execution on the EC2 instance.

$ mvn clean package

This will generate a jar file in target /.

2. Create an EC2 instance ~ Try accessing the instance from the terminal

Now let's create an EC2 instance.

Create an EC2 instance

First, let's access AWS.

** ① Move to EC2 from the service on the toolbar. ** **

** ② Click Create Instance. ** **

** ③ Select Amazon Linux at the top. ** **

** ④ Go to instance details settings **

** ⑤ Skip to the security group settings page **

** ⑥ Add rules ** Click Confirm and Create when you are done.

** ⑦ Launch instance ** Click Start to start the instance.

** ⑧ Creating a key pair ** First, enter the key pair name. After downloading, create an instance.

This completes the instance creation.

Try ssh access to your EC2 instance

Let's take a look at the instance information created earlier. ** Make a copy of the public DNS. ** **

Let's ssh access the EC2 instance using the downloaded pem file.

• You need to log in by specifying the user with ʻec2-user @ `in DNS *

$ ssh -i ~/Downloads/demo.pem ec2-user@The public DNS you copied earlier

//Let's yum update just in case
$ sudo yum update

** * Originally, place the pem file in an appropriate location such as under .ssh /. ** **

If you can access it, let's execute a nice command. (Ls, cd, etc.)

Place the jar file on your EC2 instance

Use the sftp command to place the jar file under target created locally on the ec2 instance.

Log out from the instance with ʻexit` etc. or move to the directory of the spring boot project earlier in another tab.

Now transfer the file with sftp.

$ sftp -i ~/Downloads/demo.pem ec2-user@The public DNS you copied earlier

$ sftp> put target/demo-0.0.1-SNAPSHOT.jar
Uploading target/demo-0.0.1-SNAPSHOT.jar to /home/ec2-user/demo-0.0.1-SNAPSHOT.jar
targ 100%   18MB   1.1MB/s   00:16

After the upload is complete, try logging in to your EC2 instance again.

$ ssh -i ~/Downloads/demo.pem ec2-user@The public DNS you copied earlier

 __|  __|_  )
       _|  (     /   Amazon Linux AMI
      ___|\___|___|

$ ls
demo-0.0.1-SNAPSHOT.jar

Make sure the jar file is uploaded with the ls command.

jar file execution

Now run the jar on the ec2 instance.

$ $ java -jar demo-0.0.1-SNAPSHOT.jar
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/springframework/boot/loader/JarLauncher : Unsupported major.minor version 52.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:808)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:443)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:65)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:349)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:348)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:430)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:323)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:363)
	at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)

Oops, an error has occurred. I developed with Java 1.8 locally this time, but an error occurs because the Java version included by default in Amazon linux is 1.7.

$ java -version
java version "1.7.0_201"
OpenJDK Runtime Environment (amzn-2.6.16.0.78.amzn1-x86_64 u201-b00)
OpenJDK 64-Bit Server VM (build 24.201-b00, mixed mode)

First, let's install Java 1.8.

$ sudo yum install -y java-1.8.0-openjdk.x86_64

Switch versions with the ʻalternatives` command

$ sudo alternatives --config java

There are 2 programs'java'To provide.

Select command
-----------------------------------------------
*+ 1           /usr/lib/jvm/jre-1.7.0-openjdk.x86_64/bin/java
   2           /usr/lib/jvm/jre-1.8.0-openjdk.x86_64/bin/java

Press Enter to select the current[+]Or enter the selection number:2

$ java -version
openjdk version "1.8.0_191"
OpenJDK Runtime Environment (build 1.8.0_191-b12)
OpenJDK 64-Bit Server VM (build 25.191-b12, mixed mode)

After confirming that the version has been switched, try again.

$ java -jar demo-0.0.1-SNAPSHOT.jar

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.2.RELEASE)
~
2019-02-05 02:55:55.282  INFO 8556 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
~

If you can start it safely, try accessing it from a browser or with curl.

$ curl http://DNS of the created ec2 instance:8080/person
{"name":"hoge","age":16,"gender":"man"}

Json is returned safely.

That's all for creating an API easily with EC2 + spring boot. There are many places where I broke, so it would be helpful if you could comment on the points you stumbled upon.

• It is recommended to stop the instance when not in use.

next time Try to make a simple API with EC2 + RDS + Spring boot ② * Writing