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138 lines
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<title>3. Cloud environment</title><link rel="stylesheet" type="text/css" href="css/manual-multipage.css"><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="multi_spring-cloud-aws.html" title="Spring Cloud AWS"><link rel="up" href="multi_spring-cloud-aws.html" title="Spring Cloud AWS"><link rel="prev" href="multi__basic_setup.html" title="2. Basic setup"><link rel="next" href="multi__managing_cloud_environments.html" title="4. Managing cloud environments"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">3. Cloud environment</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi__basic_setup.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="multi__managing_cloud_environments.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_cloud_environment" href="#_cloud_environment"></a>3. Cloud environment</h1></div></div></div><p>Applications often need environment specific configuration information, especially in changing environments like in the
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Amazon cloud environment. Spring Cloud AWS provides a support to retrieve and use environment specific data inside the
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application context using common Spring mechanisms like property placeholder or the Spring expression language.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_retrieving_instance_metadata" href="#_retrieving_instance_metadata"></a>3.1 Retrieving instance metadata</h2></div></div></div><p><a class="link" href="http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html" target="_top">Instance metadata</a> are available inside an
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EC2 environment. The metadata can be queried using a special HTTP address that provides the instance metadata. Spring Cloud
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AWS enables application to access this metadata directly in expression or property placeholder without the need to call
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an external HTTP service.</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_enabling_instance_metadata_support_with_xml" href="#_enabling_instance_metadata_support_with_xml"></a>3.1.1 Enabling instance metadata support with XML</h3></div></div></div><p>The instance metadata retrieval support is enabled through an XML element like the standard property placeholder in Spring.
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The following code sample demonstrates the activation of the instance metadata support inside an application context.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><beans</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">...></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute"><aws-context:context-instance-data</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"> /></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"></beans></span></pre><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Tip"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="images/tip.png"></td><th align="left">Tip</th></tr><tr><td align="left" valign="top"><p>Instance metadata can be retrieved without an authorized service call, therefore the configuration above does not require
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any region or security specific configuration.</p></td></tr></table></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_enabling_instance_metadata_support_with_java" href="#_enabling_instance_metadata_support_with_java"></a>3.1.2 Enabling instance metadata support with Java</h3></div></div></div><p>The instance metadata can also be configured within a Java configuration class without the need for an XML configuration.
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The next example shows a typical Spring <code class="literal">@Configuration</code> class that enables the instance metadata with the
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<code class="literal">org.springframework.cloud.aws.context.config.annotation.EnableInstanceData</code></p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@Configuration</span></em>
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<em><span class="hl-annotation" style="color: gray">@EnableContextInstanceData</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">static</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> ApplicationConfiguration {
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}</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_enabling_instance_metadata_support_in_spring_boot" href="#_enabling_instance_metadata_support_in_spring_boot"></a>3.1.3 Enabling instance metadata support in Spring Boot</h3></div></div></div><p>The instance metadata is automatically available in a Spring Boot application as a property source if the application
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is running on an EC2 instance.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_using_instance_metadata" href="#_using_instance_metadata"></a>3.1.4 Using instance metadata</h3></div></div></div><p>Instance metadata can be used in XML, Java placeholders and expressions. The example below demonstrates the usage of
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instance metadata inside an XML file using placeholders and also the expression referring to the special variable <code class="literal">environment</code></p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><beans</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">...></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute"><bean</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">class</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"org.springframework.cloud.aws....SimpleConfigurationBean"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag">></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><property</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">name</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"value1"</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">value</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"#{environment.ami-id}"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"> /></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><property</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">name</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"value2"</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">value</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"#{environment.hostname}"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"> /></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><property</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">name</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"value3"</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">value</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"${instance-type}"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"> /></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><property</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">name</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"value4"</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">value</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"${instance-id}"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"> /></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"></bean></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"></beans></span></pre><p>Instance metadata can also be injected with the Spring <code class="literal">org.springframework.beans.factory.annotation.Value</code> annotation
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directly into Java fields. The next example demonstrates the use of instance metadata inside a Spring bean.</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@Component</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> ApplicationInfoBean {
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<em><span class="hl-annotation" style="color: gray">@Value("${ami-id:N/A}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String amiId;
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<em><span class="hl-annotation" style="color: gray">@Value("${hostname:N/A}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String hostname;
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<em><span class="hl-annotation" style="color: gray">@Value("${instance-type:N/A}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String instanceType;
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<em><span class="hl-annotation" style="color: gray">@Value("${services/domain:N/A}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String serviceDomain;
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}</pre><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="images/note.png"></td><th align="left">Note</th></tr><tr><td align="left" valign="top"><p>Every instance metadata can be accessed by the key available in the <a class="link" href="http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html" target="_top">instance metadata service</a>
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Nested properties can be accessed by separating the properties with a slash ('/').</p></td></tr></table></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_using_instance_user_data" href="#_using_instance_user_data"></a>3.1.5 Using instance user data</h3></div></div></div><p>Besides the default instance metadata it is also possible to configure user data on each instance. This user data is retrieved and
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parsed by Spring Cloud AWS. The user data can be defined while starting an EC2 instance with the application. Spring Cloud AWS
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expects the format <code class="literal"><key>:<value>;<key>:<value></code> inside the user data so that it can parse the string and extract the key value pairs.</p><p>The user data can be configured using either the management console shown below or a <a class="link" href="http://aws.amazon.com/cloudformation/aws-cloudformation-templates/" target="_top">CloudFormation template</a>.</p><div class="informalfigure"><div class="mediaobject"><img src="images/cloud-environment-user-data.png" alt="User data in the management console"></div></div><p>A CloudFormation template snippet for the configuration of the user data is outlined below:</p><pre class="programlisting">...
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Resources"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"ApplicationServerInstance"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Type"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"AWS::EC2::Instance"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Properties"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"ImageId"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"ami-6a56b81d"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"UserData"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Fn::Base64"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"data1:value1;data2:value2"</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">},</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"InstanceType"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"t1.micro"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">}</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">}</span>
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...</pre><p>The user data can be accessed directly in the application context like the instance metadata through placeholders
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or expressions.</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@Component</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> SecondConfigurationBean {
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<em><span class="hl-annotation" style="color: gray">@Value("${data1}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String firstDataOption;
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<em><span class="hl-annotation" style="color: gray">@Value("${data2}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String secondDataOption;
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}</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_using_instance_tags" href="#_using_instance_tags"></a>3.1.6 Using instance tags</h3></div></div></div><p>User configured properties can also be configured with tags instead of user data. Tags are a global concept in the context
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of Amazon Web services and used in different services. Spring Cloud AWS supports instance tags also across different
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services. Compared to user data, user tags can be updated during runtime, there is no need to stop and restart
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the instance.</p><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Tip"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="images/tip.png"></td><th align="left">Tip</th></tr><tr><td align="left" valign="top"><p><a class="link" href="http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/user-data.html" target="_top">User data</a> can also be used to execute scripts
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on instance startup. Therefore it is useful to leverage instance tags for user configuration and user data to execute scripts
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on instance startup.</p></td></tr></table></div><p>Instance specific tags can be configured on the instance level through the management console outlined below and
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like user data also with a CloudFormation template shown afterwards.</p><div class="informalfigure"><div class="mediaobject"><img src="images/cloud-environment-instance-tags.png" alt="Instance data in the management console"></div></div><p>A CloudFormation template snippet for the configuration of the instance tags is outlined below:</p><pre class="programlisting">...
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Resources"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"UserTagAndUserDataInstance"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Type"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"AWS::EC2::Instance"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Properties"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"ImageId"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"ami-6a56b81d"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"InstanceType"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"t1.micro"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Tags"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">[</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Key"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"tag1"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Value"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"tagv1"</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">},</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Key"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"tag3"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Value"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"tagv3"</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">},</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Key"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"tag2"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Value"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"tagv2"</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">},</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">{</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Key"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"tag4"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">,</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Value"</span>: <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"tagv4"</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">}</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">]</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">}</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">}</span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">}</span>
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...</pre><p>To retrieve the instance tags, Spring Cloud AWS has to make authenticated requests and therefore it will need the region
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and security configuration before actually resolving the placeholders. Also because the instance tags are not available while starting
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the application context, they can only be referenced as expressions and not with placeholders. The <code class="literal">context-instance-data</code>
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element defines an attribute <code class="literal">user-tags-map</code> that will create a map in the application context for the name. This map
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can then be queried using expression for other bean definitions.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><beans</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">...></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute"><aws-context:context-instance-data</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">user-tags-map</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"instanceData"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"> /></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"></beans></span></pre><p>A java bean might resolve expressions with the <code class="literal">@Value</code> annotation.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> SimpleConfigurationBean {
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<em><span class="hl-annotation" style="color: gray">@Value("#{instanceData.tag1}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String value1;
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<em><span class="hl-annotation" style="color: gray">@Value("#{instanceData.tag2}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String value2;
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<em><span class="hl-annotation" style="color: gray">@Value("#{instanceData.tag3}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String value3;
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<em><span class="hl-annotation" style="color: gray">@Value("#{instanceData.tag4}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> String value4;
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}</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_configuring_custom_ec2_client" href="#_configuring_custom_ec2_client"></a>3.1.7 Configuring custom EC2 client</h3></div></div></div><p>In some circumstances it is necessary to have a custom EC2 client to retrieve the instance information. The
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<code class="literal">context-instance-data</code> element supports a custom EC2 client with the <code class="literal">amazon-ec2</code> attribute. The next
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example shows the use of a custom EC2 client that might have a special configuration in place.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><beans</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">...></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute"><aws-context:context-credentials>....</aws-context:context-credentials></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute"><aws-context:context-region</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">...</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"> /></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><aws-context:context-instance-data</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">amazon-ec2</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"myCustomClient"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag">/></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"><bean</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">id</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"myCustomClient"</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-attribute">class</span>=<span xmlns:d="http://docbook.org/ns/docbook" class="hl-value">"com.amazonaws.services.ec2.AmazonEC2Client"</span><span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag">></span>
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...
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"></bean></span>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-tag"></beans></span></pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_injecting_the_default_ec2_client" href="#_injecting_the_default_ec2_client"></a>3.1.8 Injecting the default EC2 client</h3></div></div></div><p>If there are user tags configured for the instance data (see above) Spring Cloud AWS configures an EC2 client with
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the specified region and security credentials. Application developers can inject the EC2 client directly into their code using the <code class="literal">@Autowired</code> annotation.</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> ApplicationService {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">final</span> AmazonEC2 amazonEc2;
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<em><span class="hl-annotation" style="color: gray">@Autowired</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> ApplicationService(AmazonEC2 amazonEc2) {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">this</span>.amazonEc2 = amazonEc2;
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}
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}</pre></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="multi__basic_setup.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="multi__managing_cloud_environments.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">2. Basic setup </td><td width="20%" align="center"><a accesskey="h" href="multi_spring-cloud-aws.html">Home</a></td><td width="40%" align="right" valign="top"> 4. Managing cloud environments</td></tr></table></div></body></html> |