spring servlet example. (#1939)

* spring servlet example.

* add gradle wrapper jar to fix build error.

* rename function and added configurable port number.
- also changed opencensus version to fix the maven build error.

Author: rghetia

buildscripts/import-control.xml

@@ -330,5 +330,6 @@ General guidelines on imports:
     <allow pkg="org.apache.log4j"/>
     <allow pkg="org.eclipse.jetty"/>
     <allow pkg="javax.servlet"/>
+    <allow pkg="org.springframework"/>
   </subpackage>
 </import-control>

buildscripts/travis_script

@@ -54,9 +54,11 @@ case "$TASK" in
     ;;
   "BUILD_EXAMPLES_GRADLE")
     pushd examples && ./gradlew clean assemble --stacktrace && ./gradlew check && ./gradlew verGJF && popd
+    pushd examples/spring/servlet && ./gradlew clean assemble --stacktrace && ./gradlew check && ./gradlew verGJF && popd
     ;;
   "BUILD_EXAMPLES_MAVEN")
     pushd examples && mvn clean package appassembler:assemble -e && popd
+    pushd examples/spring/servlet && mvn clean package appassembler:assemble -e && popd
     ;;
   *)
     echo "Unknown task $TASK"

examples/README.md

@@ -12,6 +12,13 @@
 mvn package appassembler:assemble
 ```
 
+To build Spring Servlet example
+```bash
+cd spring/servlet
+mvn package appassembler:assemble
+```
+
+
 ## To run "TagContextExample" use
 
 ### Gradle
@@ -162,3 +169,32 @@ Stats are available from Prometheus server running at
 
 You also need to install and start OpenCensus-Agent in order to receive the traces and metrics.
 For more information on setting up Agent, see [tutorial](https://opencensus.io/agent/).
+
+## To run Spring HTTP Server and Client
+
+`SpringServletApplication` is a web service application using Spring framework. The application
+is instrumented with opencensus simply by incuding opencensus-contrib-spring-starter package.
+The instrumentation enables tracing on incoming and outgoing http requests. On receiving GET 
+request, the server originates multiple GET requests to itself using AsyncRestTemplate on different
+endpoint.
+
+Send a http GET request using curl to see the traces on console.
+```
+curl http://localhost:8080
+```
+
+Stats are available from Prometheus server running at
+- http://localhost:9090/metrics - for server and client stats
+  
+### Gradle
+```bash
+cd spring/servlet
+./gradlew bootRun
+```
+
+### Maven
+```bash
+cd spring/servlet
+./target/appassembler/bin/SpringServletApplication
+```
+

examples/spring/servlet/.gitignore

@@ -0,0 +1,3 @@
+.mvn/**
+mvn**
+

examples/spring/servlet/application.properties

@@ -0,0 +1,2 @@
+opencensus.spring.enabled = true
+opencensus.spring.trace.publicEndpoint = false

examples/spring/servlet/build.gradle

@@ -0,0 +1,107 @@
+description = 'OpenCensus Examples Spring Servlet'
+
+buildscript {
+    repositories {
+        mavenCentral()
+        mavenLocal()
+        maven {
+            url "https://plugins.gradle.org/m2/"
+        }
+    }
+    dependencies {
+        classpath 'org.springframework.boot:spring-boot-gradle-plugin:2.0.5.RELEASE'
+        classpath 'com.github.ben-manes:gradle-versions-plugin:0.20.0'
+        classpath "gradle.plugin.com.github.sherter.google-java-format:google-java-format-gradle-plugin:0.8"
+    }
+}
+
+apply plugin: "checkstyle"
+apply plugin: 'com.github.sherter.google-java-format'
+apply plugin: 'idea'
+apply plugin: 'java'
+
+// Display the version report using: ./gradlew dependencyUpdates
+// Also see https://github.com/ben-manes/gradle-versions-plugin.
+apply plugin: 'com.github.ben-manes.versions'
+
+repositories {
+    mavenCentral()
+    mavenLocal()
+}
+
+group = "io.opencensus"
+version = "0.24.0-SNAPSHOT" // CURRENT_OPENCENSUS_VERSION
+
+def opencensusVersion = "0.23.0" // LATEST_OPENCENSUS_RELEASE_VERSION
+def prometheusVersion = "0.6.0"
+def httpasyncclientVersion = "4.1.4"
+
+
+tasks.withType(JavaCompile) {
+    sourceCompatibility = '1.8'
+    targetCompatibility = '1.8'
+}
+
+googleJavaFormat {
+    toolVersion '1.7'
+    source = 'src/main'
+    include '**/*.java'
+}
+
+verifyGoogleJavaFormat {
+    source = 'src/main'
+    include '**/*.java'
+}
+
+// Inform IDEs like IntelliJ IDEA, Eclipse or NetBeans about the generated code.
+sourceSets {
+    main {
+        java {
+            srcDir 'src'
+        }
+    }
+}
+
+checkstyle {
+    configFile = file("$rootDir/../../../buildscripts/checkstyle.xml")
+    toolVersion = "8.12"
+    ignoreFailures = false
+    configProperties["rootDir"] = "$rootDir/../../.."
+}
+
+// Disable checkstyle if no java8.
+checkstyleMain.source = 'src/main'
+checkstyleTest.source = 'src/main'
+buildscript {
+    dependencies {
+        classpath 'org.springframework.boot:spring-boot-gradle-plugin:2.0.5.RELEASE'
+    }
+}
+
+apply plugin: 'java'
+apply plugin: 'org.springframework.boot'
+apply plugin: 'io.spring.dependency-management'
+
+bootJar {
+    mainClassName = 'com.baeldung.Application'
+    baseName = 'opencensus-examples-spring-servlet'
+    version = "0.24.0-SNAPSHOT" // CURRENT_OPENCENSUS_VERSION
+}
+
+sourceCompatibility = 1.8
+targetCompatibility = 1.8
+
+dependencyManagement {
+    imports {
+        mavenBom "io.opencensus:opencensus-contrib-spring-starter:${opencensusVersion}"
+    }
+}
+
+dependencies {
+    compile("io.opencensus:opencensus-contrib-spring-starter:${opencensusVersion}")
+
+    compile("io.opencensus:opencensus-exporter-stats-prometheus:${opencensusVersion}",
+            "io.opencensus:opencensus-exporter-trace-logging:${opencensusVersion}",
+            "io.prometheus:simpleclient_httpserver:${prometheusVersion}",
+            "org.apache.httpcomponents:httpasyncclient:${httpasyncclientVersion}")
+}

examples/spring/servlet/gradle/wrapper/gradle-wrapper.jar

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.9-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists