spring-cloud/spring-cloud-config

Spring Cloud Config Server offers the following benefits:

• HTTP resource-based API for external configuration (name-value pairs or equivalent YAML content)

• Encrypt and decrypt property values (symmetric or asymmetric)

• Embeddable easily in a Spring Boot application using @EnableConfigServer

Specifically for Spring applications, Spring Cloud Config Client lets you:

• Bind to the Config Server and initialize Spring Environment with remote property sources.

• Encrypt and decrypt property values (symmetric or asymmetric).

• @RefreshScope for Spring @Beans that want to be re-initialized when configuration changes.

• Use management endpoints:

  • /env for updating Environment and rebinding @ConfigurationProperties and log levels.

  • /refresh for refreshing the @RefreshScope beans.

  • /restart for restarting the Spring context (disabled by default).

  • /pause and /resume for calling the Lifecycle methods (stop() and start() on the ApplicationContext).

• Bootstrap application context: a parent context for the main application that can be trained to do anything (by default, it binds to the Config Server and decrypts property values).

$ cd spring-cloud-config-server
$ ../mvnw spring-boot:run

$ curl localhost:8888/foo/development
{
  "name": "foo",
  "profiles": [
    "development"
  ]
  ....
  "propertySources": [
    {
      "name": "https://github.com/spring-cloud-samples/config-repo/foo-development.properties",
      "source": {
        "bar": "spam",
        "foo": "from foo development"
      }
    },
    {
      "name": "https://github.com/spring-cloud-samples/config-repo/foo.properties",
      "source": {
        "foo": "from foo props",
        "democonfigclient.message": "hello spring io"
      }
    },
    ....

/{application}/{profile}[/{label}]
/{application}-{profile}.yml
/{label}/{application}-{profile}.yml
/{application}-{profile}.properties
/{label}/{application}-{profile}.properties

curl localhost:8888/foo/development
curl localhost:8888/foo/development/master
curl localhost:8888/foo/development,db/master
curl localhost:8888/foo-development.yml
curl localhost:8888/foo-db.properties
curl localhost:8888/master/foo-db.properties

To use these features in an application, you can build it as a Spring Boot application that depends on spring-cloud-config-client (for an example, see the test cases for the config-client or the sample application). The most convenient way to add the dependency is with a Spring Boot starter org.springframework.cloud:spring-cloud-starter-config. There is also a parent pom and BOM (spring-cloud-starter-parent) for Maven users and a Spring IO version management properties file for Gradle and Spring CLI users. The following example shows a typical Maven configuration:

Now you can create a standard Spring Boot application, such as the following HTTP server:

When this HTTP server runs, it picks up the external configuration from the default local config server (if it is running) on port 8888. To modify the startup behavior, you can change the location of the config server by using application.properties as shown in the following example:

By default, if no application name is set, application will be used. To modify the name, the following property can be added to the application.properties file:

The Config Server properties show up in the /env endpoint as a high-priority property source, as shown in the following example.

A property source called configserver:<URL of remote repository>/<file name> contains the foo property with a value of bar.

You can find a sample application here. It is a Spring Boot application, so you can run it by using the usual mechanisms (for instance, mvn spring-boot:run). When it runs, it looks for the config server on http://localhost:8888 (a configurable default), so you can run the server as well to see it all working together.

The sample has a test case where the config server is also started in the same JVM (with a different port), and the test asserts that an environment property from the git configuration repo is present. To change the location of the config server, you can set spring.cloud.config.uri in bootstrap.yml (or in system properties and other places).

The test case has a main() method that runs the server in the same way (watch the logs for its port), so you can run the whole system in one process and play with it (for example, you can run the main() method in your IDE). The main() method uses target/config for the working directory of the git repository, so you can make local changes there and see them reflected in the running app. The following example shows a session of tinkering with the test case:

The refresh endpoint reports that the "sample" property changed.

To build the source you will need to install JDK 17.

Spring Cloud uses Maven for most build-related activities, and you should be able to get off the ground quite quickly by cloning the project you are interested in and typing

The projects that require middleware (i.e. Redis) for testing generally require that a local instance of [Docker](https://www.docker.com/get-started) is installed and running.

The spring-cloud-build module has a "docs" profile, and if you switch that on it will try to build asciidoc sources from src/main/asciidoc. As part of that process it will look for a README.adoc and process it by loading all the includes, but not parsing or rendering it, just copying it to ${main.basedir} (defaults to ${basedir}, i.e. the root of the project). If there are any changes in the README it will then show up after a Maven build as a modified file in the correct place. Just commit it and push the change.

If you don’t have an IDE preference we would recommend that you use Spring Tools Suite or Eclipse when working with the code. We use the m2eclipse eclipse plugin for maven support. Other IDEs and tools should also work without issue as long as they use Maven 3.3.3 or better.

Activate the Spring Maven profile

Importing into eclipse with m2eclipse

Importing into eclipse without m2eclipse

$ ./mvnw eclipse:eclipse

If you get an exception due to "Illegal key size" and you are using Sun’s JDK, you need to install the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files. See the following links for more information:

Java 6 JCE

Java 7 JCE

Java 8 JCE

Extract the JCE files into the JDK/jre/lib/security folder for whichever version of JRE/JDK x64/x86 you use.

Before we accept a non-trivial patch or pull request we will need you to sign the Contributor License Agreement. Signing the contributor’s agreement does not grant anyone commit rights to the main repository, but it does mean that we can accept your contributions, and you will get an author credit if we do. Active contributors might be asked to join the core team, and given the ability to merge pull requests.

This project adheres to the Contributor Covenant code of conduct. By participating, you are expected to uphold this code. Please report unacceptable behavior to [email protected].

None of these is essential for a pull request, but they will all help. They can also be added after the original pull request but before a merge.

• Use the Spring Framework code format conventions. If you use Eclipse you can import formatter settings using the eclipse-code-formatter.xml file from the Spring Cloud Build project. If using IntelliJ, you can use the Eclipse Code Formatter Plugin to import the same file.

• Make sure all new .java files to have a simple Javadoc class comment with at least an @author tag identifying you, and preferably at least a paragraph on what the class is for.

• Add the ASF license header comment to all new .java files (copy from existing files in the project)

• Add yourself as an @author to the .java files that you modify substantially (more than cosmetic changes).

• Add some Javadocs and, if you change the namespace, some XSD doc elements.

• A few unit tests would help a lot as well — someone has to do it.

• If no-one else is using your branch, please rebase it against the current master (or other target branch in the main project).

• When writing a commit message please follow these conventions, if you are fixing an existing issue please add Fixes gh-XXXX at the end of the commit message (where XXXX is the issue number).

Spring Cloud Build comes with a set of checkstyle rules. You can find them in the spring-cloud-build-tools module. The most notable files under the module are:

1. Default Checkstyle rules

2. File header setup

3. Default suppression rules

Checkstyle configuration

<properties>
<maven-checkstyle-plugin.failsOnError>true</maven-checkstyle-plugin.failsOnError> (1)
        <maven-checkstyle-plugin.failsOnViolation>true
        </maven-checkstyle-plugin.failsOnViolation> (2)
        <maven-checkstyle-plugin.includeTestSourceDirectory>true
        </maven-checkstyle-plugin.includeTestSourceDirectory> (3)
</properties>

<build>
        <plugins>
            <plugin> (4)
                <groupId>io.spring.javaformat</groupId>
                <artifactId>spring-javaformat-maven-plugin</artifactId>
            </plugin>
            <plugin> (5)
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-checkstyle-plugin</artifactId>
            </plugin>
        </plugins>

    <reporting>
        <plugins>
            <plugin> (5)
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-checkstyle-plugin</artifactId>
            </plugin>
        </plugins>
    </reporting>
</build>

<?xml version="1.0"?>
<!DOCTYPE suppressions PUBLIC
		"-//Puppy Crawl//DTD Suppressions 1.1//EN"
		"https://www.puppycrawl.com/dtds/suppressions_1_1.dtd">
<suppressions>
	<suppress files=".*ConfigServerApplication\.java" checks="HideUtilityClassConstructor"/>
	<suppress files=".*ConfigClientWatch\.java" checks="LineLengthCheck"/>
</suppressions>

$ curl https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/.editorconfig -o .editorconfig
$ touch .springformat

Intellij IDEA

└── src
    ├── checkstyle
    │   └── checkstyle-suppressions.xml (3)
    └── main
        └── resources
            ├── checkstyle-header.txt (2)
            ├── checkstyle.xml (1)
            └── intellij
                ├── Intellij_Project_Defaults.xml (4)
                └── Intellij_Spring_Boot_Java_Conventions.xml (5)

Figure 1. Code style

Figure 2. Inspection profiles

Spring Cloud Build brings along the basepom:duplicate-finder-maven-plugin, that enables flagging duplicate and conflicting classes and resources on the java classpath.

Duplicate Finder configuration

<build>
    <plugins>
        <plugin>
            <groupId>org.basepom.maven</groupId>
            <artifactId>duplicate-finder-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

<build>
    <plugins>
        <plugin>
            <groupId>org.basepom.maven</groupId>
            <artifactId>duplicate-finder-maven-plugin</artifactId>
            <configuration>
                <ignoredClassPatterns>
                    <ignoredClassPattern>org.joda.time.base.BaseDateTime</ignoredClassPattern>
                    <ignoredClassPattern>.*module-info</ignoredClassPattern>
                </ignoredClassPatterns>
                <ignoredResourcePatterns>
                    <ignoredResourcePattern>changelog.txt</ignoredResourcePattern>
                </ignoredResourcePatterns>
            </configuration>
        </plugin>
    </plugins>
</build>