I am using Maven and Spring Boot. I run the application using mvn spring-boot:run.
https://flywaydb.org/documentation/plugins/springboot says Flyway should be called on Spring Boot start.
So my pom.xml contains the dependency to Flyway.
<dependency>
<groupId>org.flywaydb</groupId>
<artifactId>flyway-core</artifactId>
<version>4.1.2</version>
</dependency>
The first time I ran the Maven command above it downloaded Flyway stuff, so I think the dependency is working.
I have the following files:
./src/main/resources/db/migration/V123__foo.sql
./src/main/resources/application.properties
The above article implied it should "just work", but I don't understand where it would find the JDBC URL to the database. So I added the following to the application.properties file:
flyway.url=jdbc:postgresql://localhost:5432/services?user=postgres&password=postgres
flyway.enabled=true
When Spring Boot starts up (and loads and makes available my web application) there are no logs from Flyway. I think Flyway is ignored.
What can I do? Or, more generally, how would I go about debugging this problem myself?
Nobody has posted an answer so I'll post what I found out.
M. Deinum was indeed correct in their comments to the question, the problem was a lack of a data source.
My original question was what the approach should be to debugging this kind of issue. Obviously one option is to post to stackoverflow :) But I wanted to know how to do it myself.
Spring Boot has a number of classes which look at your code and classpath, and act appropriately. For example, there are classes providing implementations to the rules like "if Flyway is on the path, and there is a data source, then execute Flyway". That rule wasn't getting triggered in my case, because I had no data source.
It's not the case that the code you write calls Spring Boot, it's the other way around, Spring Boot (external to your code) inspects your code and decides what to do based on rules. This architecture is known as action at a distance. The main problem with action at a distance is it's very difficult to debug.
The only real way to find the solution, and it was the way I went about confirming M. Deinum's diagnostic, is to read the Spring Boot source code and understand the annotations which are used to create Spring Boot code.
From the source code to Spring Boot's Flyway integration we see
#ConditionalOnClass(Flyway.class)
#ConditionalOnBean(DataSource.class)
This means "this code will get executed if Flyway is on the classpath, and if there is a DataSource bean available; otherwise it silently won't get executed".
So the answer to the question "how to debug this problem" is that there is no mechanism other than to read the source code of Spring Boot and find out how it works.
If you want to avoid this sort of problem, you have to avoid frameworks which work via "action at a distance", and that includes Spring Boot.
Related
I was trying to create a new Spring Boot project using start.spring.io. Searching for dependencies, I found that there was no AspectJ starter available. Has this dependency removed/deprecated from Spring Boot starters? Here is a screen shot:
I, however, was able to find the dependency on maven repositories website:
It was removed indeed. #jwenting explained in a nutshell why. This starer is required if you want to create your own aspect or if you want to use some advanced AOP mode.
Most users don't need it and whenever a library requires it, its starter brings it automatically. Having a dedicated entry was confusing as we saw a very large amount of users picking this up for no good reason.
Also, please keep in mind that start.spring.io is not an exhaustive list of what you can do with Spring. We're focusing on the getting started experience only and avoiding cases that could lead to confusion. This one is a good example of the latter.
it's an implicit dependency, meaning you don't have to include it because it's automatically pulled in by anything that needs it.
You can still add it explicitly, but there's no need to (and afaik it's never been needed).
I'm trying to understand why some of the micrometer MeterBinders are hooked up and others not. I can see that the MeterRegistryPostProcessor gets all of that type from context. But why is for instance JettyStatisticsMetrics not in context, but JvmGcMetrics is?
MeterBinders need to be exposed as Spring Beans in order for them to be picked up.
For Spring-Boot 1.x they need to be exposed/configured in the micrometer-spring-legacy project. For Spring-Boot 2 this is done in the spring-boot project itself.
In case you are missing some auto-configured MeterBinders, don't hesitate to file an issue in the respective bug trackers: here or here. (Please use the search. It might be these issues already have been reported.)
I'm trying Spring Batch Quick Start from Spring site (Spring Boot Quick Start) but I can't get it to work:
end() method in SimpleJobBuilder (see job method in BatchConfiguration class) is missing
When I run the main class (removing the reference to end method), Spring Boot starts up (I see the logs in the console) but the job it's not getting executed; from docs around the web I saw that the job should start as soon as the SpringApplication is run
There is something terribly wrong in Spring Batch Quick Start or there's something terribly wrong in what I'm doing?
I think it's useless to publish my code: it's copied from Spring Batch Quick Start...
Thanks for your help!
I think that little sample might be incomplete. For instance you would need #Enable AutoConfiguration in order to get a job to run on start up. There's a more extensive example here, if it helps: https://spring.io/guides/gs/batch-processing/.
In step one of the Spring Batch quick started, the guide asked to add this(the dependency below) into the pom.xml but it errored when there's no version provided. Reason being is that the guide didn't include the parent dependency. So the annotations and the java objects do not know where to look.
I got the quick guide to work by directly including the spring-boot-starter dependency. Then the app ran.. A lot of the spring framework guides seem to assume a strong knowledge in project management and comprehension tool.
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-batch</artifactId>
</dependency>
my primary attempt is to build a CRUD app using Roo, following the example here:
https://www.icts.uiowa.edu/confluence/display/ICTSit/Spring+Roo+Tutorial
I am using Roo 1.2.5, Maven 3.1.1, and Spring 3.2.6 on JRE7.
This has been the best tutorial I have found so far. If anyone has a better example, please share!
However, when I execute the project in my Tomcat environment things still break. The primary error from there is:
HTTP Status 500 -
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.NoClassDefFoundError: org/springframework/util/MimeType
I have built multiple projects using Roo over the past few days, either from this tutorial or 10 others that all start with the reverse engineer command, and all give me the same type of a NoClassDefFoundError, either with this class or another. I understand this means that my pom.xml is more than likely incorrect, but I am hoping this is an issue with my configuration rather than something all Roo developers have simply accepted as manual maintenance.
Any advice would be tremendous... is it possible that the version of Roo combined with Spring and Maven I am using is simply buggy? I would love to use this framework/toolkit, but am nearing the point where manually writing the scaffolding by hand may be more straightforward.
.... UPDATE:
By adding the following dependency manually, I was able to run the project. However, I want to leave the question open to see if anyone further knows whether this missing jar is a known bug given the version of Spring Roo I am using, or otherwise:
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.2.2</version>
</dependency>
Thanks!
The best examples are those included in Roo: clinic.roo, pizzashop.roo, etc
Just run Roo and execute any of them as follows:
/_/ |_|\____/\____/ 1.2.4.RELEASE [rev 75337cf]
Welcome to Spring Roo. For assistance press TAB or type "hint" then hit ENTER.
roo> script --file clinic.roo
On the other side, the reference doc is a good starting point: http://docs.spring.io/spring-roo/reference/html/
Finally, about java.lang.NoClassDefFoundError: org/springframework/util/MimeType note MimeType class was included in Spring 4 and Roo sets up your project for Spring 3, so you must customize the pom.xml as needed.
When we run a sample main program which reads a applicationContext.xml with a single bean..
how does Spring do the logging..and how can one overwrite the default logging.
I didnt see any log4j.xml in the spring dependencies as well..
Regards
This is described in the documentation:
Logging is a very important dependency for Spring because a) it is the only mandatory external dependency, b) everyone likes to see some output from the tools they are using, and c) Spring integrates with lots of other tools all of which have also made a choice of logging dependency. One of the goals of an application developer is often to have unified logging configured in a central place for the whole application, including all external components. This is more difficult than it might have been since there are so many choices of logging framework.
The mandatory logging dependency in Spring is the Jakarta Commons Logging API (JCL). We compile against JCL and we also make JCL Log objects visible for classes that extend the Spring Framework. It's important to users that all versions of Spring use the same logging library: migration is easy because backwards compatibility is preserved even with applications that extend Spring. The way we do this is to make one of the modules in Spring depend explicitly on commons-logging (the canonical implementation of JCL), and then make all the other modules depend on that at compile time. If you are using Maven for example, and wondering where you picked up the dependency on commons-logging, then it is from Spring and specifically from the central module called spring-core.
The nice thing about commons-logging is that you don't need anything else to make your application work. It has a runtime discovery algorithm that looks for other logging frameworks in well known places on the classpath and uses one that it thinks is appropriate (or you can tell it which one if you need to). If nothing else is available you get pretty nice looking logs just from the JDK (java.util.logging or JUL for short). You should find that your Spring application works and logs happily to the console out of the box in most situations, and that's important.
(emphasis mine)
Follow several sections describing how to use various logging frameworks.