Spring Boot Migration

[Angus Ferguson]

Hi all,

I would like to migrate a java application using Rest to Spring Boot. I am thinking in using Spring Boot Web starter for migrating an app written in Java.

Should I just "import" the code into the Spring Boot Rest app?

Regards, Isaac

[Craig Walls]

I'm not sure how to answer. Migrating existing apps to Boot have a difficulty ranging from 1 (super easy) to 10 (insanely hard, don't even try it). It kinda depends on the app you're starting with. If you're starting with an existing (non-Boot) Spring application, it might be fairly straightforward. If you're starting with some other framework, then it might be more difficult.

At the risk of giving a trite answer: It depends.

Isaac Ferguson wrote:Hi all,

I would like to migrate a java application using Rest to Spring Boot. I am thinking in using Spring Boot Web starter for migrating an app written in Java.

Should I just "import" the code into the Spring Boot Rest app?

Regards, Isaac

[Angus Ferguson]

I am starting with the migration for it I am using the Spring Initializr to create the basic structure, but which one shoudl I use?

The project to migrate contains Rest Services and credentials. Which starter should I use

Rest-Repositories

?

Regards, Isaac

[Craig Walls]

Rest-Repositories is for automatically creating REST endpoints for any repositories you may have created with Spring Data. If you are using Doring Data, it’s certainly worth looking into.

For creating your own REST endpoints, not necessarily associated with a Spring Data repository, you should pick either Spring MVC (Web) or Spring WebFlux (Reactive Web). The choice here hinges on whether you are ready to go reactive in your app.

Isaac Ferguson wrote:I am starting with the migration for it I am using the Spring Initializr to create the basic structure, but which one shoudl I use?

The project to migrate contains Rest Services and credentials. Which starter should I use

Rest-Repositories

?

Regards, Isaac

[Angus Ferguson]

I have choosen Spring MVC, Security and Jersey.

Jersey for REST, Security for authentication and Spring MVC?

[Tim Holloway]

You might want to look at Spring REST: https://spring.io/guides/gs/rest-service/ as it seems to be illustrating something along what you're talking about.

In most cases, Spring modules are built on top of general modules, such as Spring JPA's ability to use Hibernate. And in fact, when you have a standard interface (such as JPA), often the underlying module is plug-replaceable.

So there's a very good chance that you could use Jersey and leverage it using Spring REST.

[Angus Ferguson]

Spring JPA's ability to use Hibernate

The app I need to migrate it is only Rest and Authetication without persistence I understand that Spring Rest is usd when there is persistence.

[Angus Ferguson]

You might want to look at Spring REST: https://spring.io/guides/gs/rest-service

This is Spring but I want to use Spring Boot and the right starter.

[Angus Ferguson]

http://www.springboottutorial.com/creating-rest-service-with-spring-boot

[Tim Holloway]

Isaac Ferguson wrote:

You might want to look at Spring REST: https://spring.io/guides/gs/rest-service

This is Spring but I want to use Spring Boot and the right starter.

Read it more carefully. There's Spring Boot sample code in there.

Also, I question that Spring REST requires persistence. Spring has a whole separate module realm for persistence and they don't tend to lump unrelated functions together.

[Angus Ferguson]

package hello;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

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

Yes this is to make it executable...

[Angus Ferguson]

In fact for security I would like to use LDAP.

[Angus Ferguson]

When starting the migration and I set up the basic Spring Boot structure I get the next error in the pom.xml.

Plugin execution not covered by lifeclicle configuration: org.apache.maven.plugins : maven-resources-plugin:3.1.0:(execution : default-testResources, phase:testResources.processs-test-resource)

[Angus Ferguson]

The pom.xml is this one:

<?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>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.0.RELEASE</version>
		
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>datev.notifications.spring</groupId>
	<artifactId>notifications.spring</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>notifications.spring</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-actuator</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-devtools</artifactId>
			<scope>runtime</scope>
		</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>

[Angus Ferguson]

I am migrating a Java 2 EE app to Spring Boot and I ask myself which of the next Java EE2 could be correlated with Spring Boot. The same way that we can substitute @Inject by @Autowired.

import javax.mail.internet.MimeMessage;
import javax.ws.rs.core.Response;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.ws.rs.Path;
import javax.ws.rs.core.Response;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

The question is which ones have a Spring Boot counterpart.

[Angus Ferguson]

Basically all is about using this dependency in the code.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-mail</artifactId>
    <version>2.0.0.RELEASE</version>
</dependency>

[Rob Spoor]

First of all, I'd upgrade to the latest Spring Boot version, 2.1.1.RELEASE.

You can see the classes related to email sending in Spring (Boot) here:
* https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/mail/package-summary.html
* https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/mail/javamail/package-summary.html

In this case, JavaMailSender is the interface to inject. You can use MimeMessageHelper and MimeMessagePreparator to create the actual message. An example can be found on https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/mail/javamail/MimeMessageHelper.html. However, since MimeMessagePreparator is a functional interface, you can shorten that example:

mailSender.send(mimeMessage -> {
    MimeMessageHelper message = new MimeMessageHelper(mimeMessage, true, "UTF-8");
    message.setFrom("[e-mail]");
    message.setTo("[e-mail]");
    message.setSubject("my subject");
    message.setText("my text <img >", true);
    message.addInline("myLogo", new ClassPathResource("img/mylogo.gif"));
    message.addAttachment("myDocument.pdf", new ClassPathResource("doc/myDocument.pdf"));
});

[Angus Ferguson]

I am trying to use two @RestControllers in two dfferent classes and within each of them several @RequestMapping.

One of them follows the path /v1 it works and it is reflected in the tab Spring Elements.

The other class is in a different package within src/main/java but it is not automatically reflected in the tab Spring Element and is it not called when the app calls its path "v2"

Any strategy to make it works with v2?

[Rob Spoor]

Can you give us the fully qualified names of these two classes, and the fully qualified name and annotations of the class annotated with @SpringBootApplication?

My guess is that the second class does not share a package structure with the @SpringBootApplication. If that's the case, you need to explicitly use @ComponentScan to include both sets of packages. @SpringBootApplication implies @ComponentScan without explicit packages / classes which is the same as @ComponentScan with the @SpringBootApplication class' package. If you use @ComponentScan you do not get this package for free anymore, that's why you need to add both sets.

[Angus Ferguson]

Can you give us the fully qualified names of these two classes

@RestController
@RequestMapping("/v1")
/org.springframework.boot/src/main/java/ddddd/nton/rt/a/NtonController.java

@RestController
@RequestMapping("/v2")
/org.springframework.boot/src/main/java/ddddd/nton/v1/b/Nton.java

and the fully qualified name and annotations of the class annotated with @SpringBootApplication?

@SpringBootApplication
/org.springframework.boot/src/main/java/ddddd/nton/rt/a/Nton.java

[Angus Ferguson]

Sorry I pur quotes instead of "code"

[Angus Ferguson]

•spring.mail.host – Email server host 
•spring.mail.port – Email port 
•spring.mail.username – Email server username 
•spring.mail.password – Email server password 
•spring.mail.jndi-name – Session jndi name. If set overrides other properties 
•spring.mail.protocol – Protocol for email (smtp) 
•spring.mail.properties.* – JavaMail session properties 

Where should be this data located in the original JEE app? I need to migrate it to the springmail.properties ->application.properties

[Angus Ferguson]

For example when I comment @ComponentScan({ "ddddd.nton.v1.b"}) it works, but when not I get ERR_CONNECTION_REFUSED in the browser.

package ddddd.nton.rt.a;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;


//@ComponentScan({ "ddddd.nton.v1.b"})
@SpringBootApplication
public class DdddNotnoApp {

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

[Rob Spoor]

Just as I thought, the v1 controller shares a package structure with the @SpringBootApplication class. Both are in package ddddd.nton.rt.a, whereas the v2 controller lives in package ddddd.nton.v1.b (which is a odd, the versions don't match).

You have a few options:
1) Use @ComponentScan("ddddd.nton") to include everything under dddd.nton.
2) Use @ComponentScan({"dddd.nton.rt.a", "dddd.nton.v1.b"}) to include these exact two packages (and sub packages).
3) Like 2 put some combination of base packages (e.g. dddd.nton.rt and/or dddd.nton.v1).
4) Like 2 or 3 but using basePackageClasses (possibly with basePackages) with some classes instead of package names.

Isaac Ferguson wrote:Where should be this data located in the original JEE app? I need to migrate it to the springmail.properties ->application.properties

I think that depends on your container. In WebLogic those were defined in a mail session in the admin console. I can't remember how JBoss did it, and I've never really used GlassFish.

[Angus Ferguson]

When I add the @ComponentScan({"dddd.nton.rt.a", "dddd.nton.v1.b"}) I get

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


There was an unexpected error (type=Not Found, status=404).
No message available

The same if I put the packages in different @ComponentScan

[Angus Ferguson]

I added the next annotations

@ComponentScan({"dddd.nton.rt.a", "dddd.nton.v1.b"}) 
@ComponentScan(basePackageClasses=ClassNameController.class)
@ComponentScan(basePackageClasses=dddd.nton.v1.b.ClassName_1.class)
@ComponentScan(basePackageClasses=packageAndName_DontfoundClass.class)
@Component
@SpringBootApplication
public class ExampleApplication {

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

Description:

Field serviceC in dddd.nton.v1.b.ClassName_1 required a bean of type 'package.ServiceC' that could not be found.

The injection point has the following annotations:
	- @org.springframework.beans.factory.annotation.Autowired(required=true)


Action:

Consider defining a bean of type 'package.ServiceC' in your configuration.

[Angus Ferguson]

'package.ServiceC' 

it is an interface.

[Angus Ferguson]

I am migrating a JEE application to Spring Boot.Originally in JEE I had this code

private static final Logger Logger = LogManager.getLogger(LoggingController.class.getName());

After reading about Spring Boot loggers looks like it should be done like this:

private static final org.slf4j.Logger logger = LoggerFactory.getLogger(LoggingController.class);

Later in the code it is written;

catch (NamingException e) {
			 Logger.error("Exception: " + e.toString());
		}

Should the logs go into the console or to a particular file?

[Rob Spoor]

It depends on your logging configuration. I don't really know the defaults, but you can use a logback-spring.xml configuration file to change it. Alternatively, you can use the logging properties defined at https://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html to configure them in your application.properties.

[Rob Spoor]

Isaac Ferguson wrote:

'package.ServiceC' 

it is an interface.

Do you have an annotated implementation for this interface? For some interfaces Spring Boot can create implementations (e.g. CrudRepository), but definitely not all.