[[quick-start]]
= Quick Start

This quick start walks through using Spring Cloud Zookeeper for Service Discovery and Distributed Configuration.

First, run Zookeeper on your machine. Then you can access it and use it as a Service Registry and Configuration source with Spring Cloud Zookeeper.

[[discovery-client-usage]]
== Discovery Client Usage

To use these features in an application, you can build it as a Spring Boot application that depends on `spring-cloud-zookeeper-core` and `spring-cloud-zookeeper-discovery`.
The most convenient way to add the dependency is with a Spring Boot starter: `org.springframework.cloud:spring-cloud-starter-zookeeper-discovery`.
We recommend using dependency management and `spring-boot-starter-parent`.
The following example shows a typical Maven configuration:

[source,xml,indent=0]
.pom.xml
----
<project>
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>{spring-boot-version}</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>

  <dependencies>
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies</artifactId>
        <version>${spring-cloud.version}</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>
  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>
----

The following example shows a typical Gradle setup:

[source,groovy,indent=0]
.build.gradle
----
plugins {
  id 'org.springframework.boot' version ${spring-boot-version}
  id 'io.spring.dependency-management' version ${spring-dependency-management-version}
  id 'java'
}

repositories {
  mavenCentral()
}

dependencies {
  implementation 'org.springframework.cloud:spring-cloud-starter-zookeeper-discovery'
  testImplementation 'org.springframework.boot:spring-boot-starter-test'
}
dependencyManagement {
  imports {
    mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
  }
}
----

WARNING: Depending on the version you are using, you might need to adjust Apache Zookeeper version used in your project.
You can read more about it in the xref:install.adoc[Install Zookeeper section].

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

----
@SpringBootApplication
@RestController
public class Application {

    @GetMapping("/")
    public String home() {
        return "Hello World!";
    }

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

}
----

When this HTTP server runs, it connects to Zookeeper, which runs on the default local port (2181).
To modify the startup behavior, you can change the location of Zookeeper by using `application.properties`, as shown in the following example:

----
spring:
  cloud:
    zookeeper:
      connect-string: localhost:2181
----

You can now use `DiscoveryClient`, `@LoadBalanced RestTemplate`, or `@LoadBalanced WebClient.Builder` to retrieve services and instances data from Zookeeper, as shown in the following example:

[source,java,indent=0]
----
@Autowired
private DiscoveryClient discoveryClient;

public String serviceUrl() {
    List<ServiceInstance> list = discoveryClient.getInstances("STORES");
    if (list != null && list.size() > 0 ) {
        return list.get(0).getUri().toString();
    }
    return null;
}
----

[[distributed-configuration-usage]]
== Distributed Configuration Usage

To use these features in an application, you can build it as a Spring Boot application that depends on `spring-cloud-zookeeper-core` and `spring-cloud-zookeeper-config`.
The most convenient way to add the dependency is with a Spring Boot starter: `org.springframework.cloud:spring-cloud-starter-zookeeper-config`.
We recommend using dependency management and `spring-boot-starter-parent`.
The following example shows a typical Maven configuration:

[source,xml,indent=0]
.pom.xml
----
<project>
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>{spring-boot-version}</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>

  <dependencies>
    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-zookeeper-config</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies</artifactId>
        <version>${spring-cloud.version}</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>
  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>
----

The following example shows a typical Gradle setup:

[source,groovy,indent=0]
.build.gradle
----
plugins {
  id 'org.springframework.boot' version ${spring-boot-version}
  id 'io.spring.dependency-management' version ${spring-dependency-management-version}
  id 'java'
}

repositories {
  mavenCentral()
}

dependencies {
  implementation 'org.springframework.cloud:spring-cloud-starter-zookeeper-config'
  testImplementation 'org.springframework.boot:spring-boot-starter-test'
}
dependencyManagement {
  imports {
    mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
  }
}
----

WARNING: Depending on the version you are using, you might need to adjust Apache Zookeeper version used in your project.
You can read more about it in the xref:install.adoc[Install Zookeeper section].

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

----
@SpringBootApplication
@RestController
public class Application {

    @GetMapping("/")
    public String home() {
        return "Hello World!";
    }

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

}
----

The application retrieves configuration data from Zookeeper.

WARNING: If you use Spring Cloud Zookeeper Config, you need to set the `spring.config.import` property in order to bind to Zookeeper.
You can read more about it in the xref:config.adoc#config-data-import[Spring Boot Config Data Import section].
