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2018-10-01 10:40:05 +00:00
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@@ -31,12 +31,14 @@ We search for a <code class="literal">TagValueExpressionResolver</code> bean.
The default implementation uses SPEL expression resolution.
<span class="strong"><strong>IMPORTANT</strong></span> You can only reference properties from the SPEL expression. Method execution is not allowed due to security constraints.</li><li class="listitem">If we do not find any expression to evaluate, return the <code class="literal">toString()</code> value of the parameter.</li></ol></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_custom_extractor" href="#_custom_extractor"></a>11.4.1&nbsp;Custom extractor</h3></div></div></div><p>The value of the tag for the following method is computed by an implementation of <code class="literal">TagValueResolver</code> interface.
Its class name has to be passed as the value of the <code class="literal">resolver</code> attribute.</p><p>Consider the following annotated method:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@NewSpan</span></em>
<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> getAnnotationForTagValueResolver(<em><span class="hl-annotation" style="color: gray">@SpanTag(key = "test", resolver = TagValueResolver.class)</span></em> String test) {
<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> getAnnotationForTagValueResolver(
<em><span class="hl-annotation" style="color: gray">@SpanTag(key = "test", resolver = TagValueResolver.class)</span></em> String test) {
}</pre><p>Now further consider the following <code class="literal">TagValueResolver</code> bean implementation:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@Bean(name = "myCustomTagValueResolver")</span></em>
<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> TagValueResolver tagValueResolver() {
<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> parameter -&gt; <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Value from myCustomTagValueResolver"</span>;
}</pre><p>The two preceding examples lead to setting a tag value equal to <code class="literal">Value from myCustomTagValueResolver</code>.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_resolving_expressions_for_a_value" href="#_resolving_expressions_for_a_value"></a>11.4.2&nbsp;Resolving Expressions for a Value</h3></div></div></div><p>Consider the following annotated method:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@NewSpan</span></em>
<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> getAnnotationForTagValueExpression(<em><span class="hl-annotation" style="color: gray">@SpanTag(key = "test", expression = "'hello' + ' characters'")</span></em> String test) {
<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> getAnnotationForTagValueExpression(
<em><span class="hl-annotation" style="color: gray">@SpanTag(key = "test", expression = "'hello' + ' characters'")</span></em> String test) {
}</pre><p>No custom implementation of a <code class="literal">TagValueExpressionResolver</code> leads to evaluation of the SPEL expression, and a tag with a value of <code class="literal">4 characters</code> is set on the span.
If you want to use some other expression resolution mechanism, you can create your own implementation of the bean.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_using_the_tostring_method" href="#_using_the_tostring_method"></a>11.4.3&nbsp;Using the <code class="literal">toString()</code> method</h3></div></div></div><p>Consider the following annotated method:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@NewSpan</span></em>
<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> getAnnotationForArgumentToString(<em><span class="hl-annotation" style="color: gray">@SpanTag("test")</span></em> Long param) {