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if-else control flow
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modified by <a href="https://community.jboss.org/people/ctomc">Tomaz Cerar</a> in <i>JBoss AS 7 Development</i> - <a href="https://community.jboss.org/docs/DOC-18764">View the full document</a>
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<div class="jive-rendered-content"><h4>if-else controll flow was introduced in 7.2 builds</h4><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>With if-else control flow you can choose which set of commands and operations to execute based on a condition. The condition is a boolean expression which evaluates the response of the operation (or command) specified in the if statement. Let's look at an example</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><pre class="jive-pre"><code class="jive-code">
if (outcome != success) of /system-property=test:read-resource
    /system-property=test:add(value=true)
end-if</code></pre><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>The <strong>if</strong> statement can be read as "if the outcome attribute of /system-property=test:read-resource response is not success (which means the property does not exist) then add the property and initialize it to true".</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>To understand the condition expression better, the result of <em>/system-property=test:read-resource</em> if the test property doesn't exist will be</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><pre class="jive-pre"><code class="jive-code">[standalone@localhost:9999 /] /system-property=test:read-resource
{
    "outcome" => "failed",
    "failure-description" => "JBAS014807: Management resource '[(\"system-property\" => \"test\")]' not found",
    "rolled-back" => true
}</code></pre><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>You can see that the <strong>outcome</strong> attribute equals <strong>failed</strong>, so the expression in our <strong>if</strong> statement will evaluate to true and the body of the <strong>if</strong> will be executed. If we execute <em>read-resource</em> after the <strong>if</strong> again we'll see</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><pre class="jive-pre"><code class="jive-code">[standalone@localhost:9999 /] /system-property=test:read-resource
{
    "outcome" => "success",
    "result" => {"value" => "true"}
}</code></pre><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Here is another example which demonstrates <strong>if</strong> with <strong>else</strong> and inverts the true-false value every time it's executed. It also shows how you can navigate the response, i.e. it evaluates attribute <strong>value</strong> - the child <strong>result</strong> - using a dot.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><pre class="jive-pre"><code class="jive-code">
if (result.value == true) of /system-property=test:read-resource
    /system-property=test:write-attribute(name=value,value=false)
else
    /system-property=test:write-attribute(name=value,value=true)
end-if</code></pre><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>The <strong>of</strong> keyword can be followed by any management command or an operation which results in a response from the controller.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>And condition expressions can contain</p><p>• boolean && (and), || (or) and parentheses to group and prioritize expressions;</p><p>• >, >=, < and <= in addition to == and !=;</p><p>• the whitespaces are insignificant and ignored.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>E.g. something like this could be a valid condition expression: ((a==b || c.c1<=d && e.e1.e2>f) && g!=h || i>=j) && (k<l && m>n || o==p)</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>If you use a navigation path and the path doesn't exist then the expression (the comparison which involves the path) will evaluate to false.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>The examples above are simple and show only one operation in the bodies of the <strong>if</strong> and <strong>else</strong> but there is no such limitation. Each if/else body is a batch (which will be translated into a single composite operation) and can contain any number of commands and operations. Although, nested if-else and try-catch-finally are not yet supported.</p></div>
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