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1# spring
2[![Build Status][travis-image]][travis-url]
3[![Windows Build Status][appveyor-image]][appveyor-url]
4[![Maven Central][maven-image]][maven-url]
5
6Provides annotation support for projects that use Spring.
7
8## Quickstart
9
10### Add the dependencies to your project.
11
12Replace `SPRING_VERSION` with the version of spring you're using.
13
14For Maven add to your `pom.xml`:
15```xml
16<dependencies>
17  <!-- census -->
18  <dependency>
19    <groupId>io.opencensus</groupId>
20    <artifactId>opencensus-api</artifactId>
21    <version>0.16.1</version>
22  </dependency>
23  <dependency>
24    <groupId>io.opencensus</groupId>
25    <artifactId>opencensus-contrib-spring</artifactId>
26    <version>0.16.1</version>
27  </dependency>
28  <dependency>
29    <groupId>io.opencensus</groupId>
30    <artifactId>opencensus-impl</artifactId>
31    <version>0.16.1</version>
32    <scope>runtime</scope>
33  </dependency>
34
35  <!-- spring aspects -->
36  <dependency>
37    <groupId>org.springframework</groupId>
38    <artifactId>spring-aspects</artifactId>
39    <version>SPRING_VERSION</version>
40    <scope>runtime</scope>
41  </dependency>
42
43</dependencies>
44```
45
46For Gradle add to your dependencies:
47```gradle
48compile 'io.opencensus:opencensus-api:0.16.1'
49compile 'io.opencensus:opencensus-contrib-spring:0.16.1'
50runtime 'io.opencensus:opencensus-impl:0.16.1'
51runtime 'org.springframework:spring-aspects:SPRING_VERSION'
52```
53
54### Features
55
56#### Traced Annotation
57
58The `opencensus-contrib-spring` package provides support for a `@Traced` annotation
59that can be applied to methods.  When applied, the method will be wrapped in a
60Span, [https://github.com/census-instrumentation/opencensus-specs/blob/master/trace/Span.md](https://github.com/census-instrumentation/opencensus-specs/blob/master/trace/Span.md)
61
62If the method throws an exception, the `Span` will be marked with a status of `Status.UNKNOWN`
63and the stack trace will be added to the span as an annotation.
64
65To enable the `@Traced` annotation, include the `CensusSpringAspect` bean.
66
67```xml
68  <!-- traces explicit calls to Traced -->
69  <bean id="censusAspect" class="io.opencensus.contrib.spring.aop.CensusSpringAspect">
70    <constructor-arg ref="tracer"/>
71  </bean>
72```
73
74#### Database Support
75
76The `opencensus-contrib-spring` package also includes support for tracing database
77calls.  When database support is included, all calls to `java.sql.PreparedStatement.execute*`
78will be wrapped in a Span in the same way that `@Traced` wraps methods.
79
80To enable database support, include the `CensusSpringSqlAspect` bean.
81
82```xml
83  <!-- traces all SQL calls -->
84  <bean id="censusSQLAspect" class="io.opencensus.contrib.spring.aop.CensusSpringSqlAspect">
85    <constructor-arg ref="tracer"/>
86  </bean>
87```
88
89#### Complete Spring XML configuration
90
91The following contains a complete spring xml file to configure `opencensus-contrib-spring`
92with support for both `@Traced` and database connection tracing.
93
94**Note:** This example does not include the configuration of any exporters. That will
95need to be done separately.
96
97**TBD:*** Include examples of spring with exporters.
98
99```xml
100<beans xmlns="http://www.springframework.org/schema/beans"
101       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
102       xmlns:aop="http://www.springframework.org/schema/aop"
103       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
104
105  <aop:aspectj-autoproxy/>
106
107  <!-- traces explicit calls to Traced -->
108  <bean id="censusAspect" class="io.opencensus.contrib.spring.aop.CensusSpringAspect">
109    <constructor-arg ref="tracer"/>
110  </bean>
111
112  <!-- traces all SQL calls -->
113  <bean id="censusSQLAspect" class="io.opencensus.contrib.spring.aop.CensusSpringSqlAspect">
114    <constructor-arg ref="tracer"/>
115  </bean>
116
117  <!-- global tracer -->
118  <bean id="tracer" class="io.opencensus.trace.Tracing" factory-method="getTracer"/>
119</beans>
120```
121
122### Traced Usage
123
124Once configured, you can use the `@Traced` annotation to indicate that a method should
125be wrapped with a `Span`.  By default, `@Traced` will use the name of the method as the
126span name.  However, `@Traced` supports an optional name attribute to allow a custom
127span name to be specified.
128
129```java
130  @Traced()
131  void example1() {
132    // do work
133  }
134
135  // a custom span name can also be provided to Traced
136  @Traced(name = "custom-span-name")
137  void example2() {
138    // do moar work
139  }
140```
141
142#### Notes
143
144`opencensus-contrib-spring` support only enables annotations.  You will still need to configure opencensus and register exporters / views.
145
146[travis-image]: https://travis-ci.org/census-instrumentation/opencensus-java.svg?branch=master
147[travis-url]: https://travis-ci.org/census-instrumentation/opencensus-java
148[appveyor-image]: https://ci.appveyor.com/api/projects/status/hxthmpkxar4jq4be/branch/master?svg=true
149[appveyor-url]: https://ci.appveyor.com/project/opencensusjavateam/opencensus-java/branch/master
150[maven-image]: https://maven-badges.herokuapp.com/maven-central/io.opencensus/opencensus-contrib-spring/badge.svg
151[maven-url]: https://maven-badges.herokuapp.com/maven-central/io.opencensus/opencensus-contrib-spring
152
153#### Java Versions
154
155Java 6 or above is required for using this artifact.
156
157#### About the `aop` package
158
159`opencensus-contrib-spring` makes heavy use of Aspect Oriented Programming [AOP](https://en.wikipedia.org/wiki/Aspect-oriented_programming) to
160add behavior to annotations.  Fortunately, Spring supports this natively so we can leverage the capabilities they've already built in.
161