add spring starter package for opencensus spring integration. (#1934)

* add spring starter package for opencensus spring integration.

* remove duplicate links.

* fix build error.

3 files changed, 103 insertions, 0 deletions

diff --git a/contrib/spring_starter/README.md b/contrib/spring_starter/README.md
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+# OpenCensus Spring Starter
+[![Build Status][travis-image]][travis-url]
+[![Windows Build Status][appveyor-image]][appveyor-url]
+[![Maven Central][maven-image]][maven-url]
+
+The *OpenCensus Spring Starter for Java* is a starter package that includes
+packages required to enable tracing using opencensus when working with [Spring Web][spring-web-url].
+
+This version is compatible with [Spring Boot 2.0][spring-boot-2.0-url].
+
+## Servlet and AsyncRestTemplate Tracing
+
+Enable tracing on RestController (server side) and AysncRestTemplate (client side) by simply including opencensus-contrib-spring-starter in your dependencies and
+initializing exporter. It automatically traces your http request and collects stats associated with the
+request.
+
+It does require to register exporter and views.
+
+### Depedencies
+
+#### Maven
+
+```xml
+<dependencies>
+    <dependency>
+        <groupId>io.opencensus</groupId>
+        <artifactId>opencensus-contrib-spring-starter</artifactId>
+        <version>0.23.0</version>
+    </dependency>
+</dependencies>
+
+```
+
+#### Gradle
+```gradle
+dependencyManagement {
+    imports {
+        mavenBom "io.opencensus:opencensus-contrib-spring-starter:0.23.0"
+    }
+}
+dependencies {
+	compile 'io.opencensus:opencensus-contrib-spring:0.23.0'
+}
+```
+
+### Tracing Properties
+
+Optionally configure one or more Tracing Properties in application.properties file.
+
+
+#### PublicEndpoint
+
+If a servlet is serving publicEndpoints (untrusted boundary) then set this property to `true`. 
+When set to true incoming trace context is added as a parent link instead of as a parent.
+By default it is set to `false`. When set to `false` it uses incoming trace context as a parent.
+
+```
+opencensus.spring.trace.publicEndpoint = true
+```
+
+#### Propagation
+
+opencensus.spring.trace.propagation = TRACE_PROPAGATION_B3
+
+By default it is set to TRACE_PROPAGATION_TRACE_CONTEXT which uses [W3C Tracecontext](https://github.com/census-instrumentation/opencensus-java/blob/master/api/src/main/java/io/opencensus/trace/propagation/TextFormat.java)
+propagator to propagate trace context. To use [B3 format](https://github.com/census-instrumentation/opencensus-java/blob/master/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/B3Format.java) 
+set the property to TRACE_PROPAGATION_B3
+
+```
+opencensus.spring.trace.propagation = TRACE_PROPAGATION_B3
+```
+
+#### Java Versions
+
+Java 6 or above is required for using this artifact.
+
+[travis-image]: https://travis-ci.org/census-instrumentation/opencensus-java.svg?branch=master
+[travis-url]: https://travis-ci.org/census-instrumentation/opencensus-java
+[appveyor-image]: https://ci.appveyor.com/api/projects/status/hxthmpkxar4jq4be/branch/master?svg=true
+[appveyor-url]: https://ci.appveyor.com/project/opencensusjavateam/opencensus-java/branch/master
+[maven-image]: https://maven-badges.herokuapp.com/maven-central/io.opencensus/opencensus-contrib-spring-starter/badge.svg
+[maven-url]: https://maven-badges.herokuapp.com/maven-central/io.opencensus/opencensus-contrib-spring-starter
+[spring-boot-2.0-url]: https://github.com/spring-projects/spring-boot/tree/2.0.x
+[spring-web-url]: https://github.com/spring-projects/spring-framework/tree/master/spring-web
diff --git a/contrib/spring_starter/build.gradle b/contrib/spring_starter/build.gradle
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+plugins {
+    id 'java'
+}
+
+description = 'OpenCensus Spring Cloud Starter'
+
+[compileJava, compileTestJava].each() {
+    it.sourceCompatibility = 1.6
+    it.targetCompatibility = 1.6
+}
+
+dependencies {
+    compile project(':opencensus-api'),
+            project(':opencensus-contrib-spring'),
+            project(':opencensus-impl')
+
+    signature "org.codehaus.mojo.signature:java16:+@signature"
+}
diff --git a/contrib/spring_starter/src/main/resources/META-INF/spring.provides b/contrib/spring_starter/src/main/resources/META-INF/spring.provides
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index 00000000..ffe5e4d4
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+++ b/contrib/spring_starter/src/main/resources/META-INF/spring.provides
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+provides: opencensus-contrib-spring
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