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| <div class="sub-title"><span class="package-label-in-type">Package</span> <a href="package-summary.html">org.apache.logging.log4j.core</a></div> |
| <h1 title="Interface ContextDataInjector" class="title">Interface ContextDataInjector</h1> |
| </div> |
| <section class="class-description" id="class-description"> |
| <dl class="notes"> |
| <dt>All Known Implementing Classes:</dt> |
| <dd><code><a href="impl/ThreadContextDataInjector.ForCopyOnWriteThreadContextMap.html" title="class in org.apache.logging.log4j.core.impl">ThreadContextDataInjector.ForCopyOnWriteThreadContextMap</a></code>, <code><a href="impl/ThreadContextDataInjector.ForDefaultThreadContextMap.html" title="class in org.apache.logging.log4j.core.impl">ThreadContextDataInjector.ForDefaultThreadContextMap</a></code>, <code><a href="impl/ThreadContextDataInjector.ForGarbageFreeThreadContextMap.html" title="class in org.apache.logging.log4j.core.impl">ThreadContextDataInjector.ForGarbageFreeThreadContextMap</a></code></dd> |
| </dl> |
| <hr> |
| <div class="type-signature"><span class="modifiers">public interface </span><span class="element-name type-name-label">ContextDataInjector</span></div> |
| <div class="block">Responsible for initializing the context data of LogEvents. Context data is data that is set by the application to be |
| included in all subsequent log events. |
| <p><b>NOTE: It is no longer recommended that custom implementations of this interface be provided as it is |
| difficult to do. Instead, provide a custom ContextDataProvider.</b></p> |
| <p> |
| <p> |
| The source of the context data is implementation-specific. The default source for context data is the ThreadContext. |
| </p><p> |
| In some asynchronous models, work may be delegated to several threads, while conceptually this work shares the same |
| context. In such models, storing context data in <code>ThreadLocal</code> variables is not convenient or desirable. |
| Users can configure the <code>ContextDataInjectorFactory</code> to provide custom <code>ContextDataInjector</code> objects, |
| in order to initialize log events with context data from any arbitrary context. |
| </p><p> |
| When providing a custom <code>ContextDataInjector</code>, be aware that the <code>ContextDataInjectorFactory</code> may be |
| invoked multiple times and the various components in Log4j that need access to context data may each have their own |
| instance of <code>ContextDataInjector</code>. |
| This includes the object(s) that populate log events, but also various lookups and filters that look at |
| context data to determine whether an event should be logged. |
| </p><p> |
| Implementors should take particular note of how the different methods in the interface have different thread-safety |
| guarantees to enable optimal performance. |
| </p></div> |
| <dl class="notes"> |
| <dt>Since:</dt> |
| <dd>2.7</dd> |
| <dt>See Also:</dt> |
| <dd> |
| <ul class="see-list"> |
| <li><a href="https://logging.apache.org/log4j/2.x/apidocs/org/apache/logging/log4j/util/StringMap.html" title="class or interface in org.apache.logging.log4j.util" class="external-link"><code>StringMap</code></a></li> |
| <li><a href="https://logging.apache.org/log4j/2.x/apidocs/org/apache/logging/log4j/util/ReadOnlyStringMap.html" title="class or interface in org.apache.logging.log4j.util" class="external-link"><code>ReadOnlyStringMap</code></a></li> |
| <li><a href="impl/ContextDataInjectorFactory.html" title="class in org.apache.logging.log4j.core.impl"><code>ContextDataInjectorFactory</code></a></li> |
| <li><a href="https://logging.apache.org/log4j/2.x/apidocs/org/apache/logging/log4j/ThreadContext.html" title="class or interface in org.apache.logging.log4j" class="external-link"><code>ThreadContext</code></a></li> |
| <li><a href="impl/ThreadContextDataInjector.html" title="class in org.apache.logging.log4j.core.impl"><code>ThreadContextDataInjector</code></a></li> |
| </ul> |
| </dd> |
| </dl> |
| </section> |
| <section class="summary"> |
| <ul class="summary-list"> |
| <!-- ========== METHOD SUMMARY =========== --> |
| <li> |
| <section class="method-summary" id="method-summary"> |
| <h2>Method Summary</h2> |
| <div id="method-summary-table"> |
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| <div class="summary-table three-column-summary" aria-labelledby="method-summary-table-tab0"> |
| <div class="table-header col-first">Modifier and Type</div> |
| <div class="table-header col-second">Method</div> |
| <div class="table-header col-last">Description</div> |
| <div class="col-first even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="https://logging.apache.org/log4j/2.x/apidocs/org/apache/logging/log4j/util/StringMap.html" title="class or interface in org.apache.logging.log4j.util" class="external-link">StringMap</a></code></div> |
| <div class="col-second even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="#injectContextData(java.util.List,org.apache.logging.log4j.util.StringMap)" class="member-name-link">injectContextData</a><wbr>(<a href="https://docs.oracle.com/javase/8/docs/api/java/util/List.html" title="class or interface in java.util" class="external-link">List</a><<a href="config/Property.html" title="class in org.apache.logging.log4j.core.config">Property</a>> properties, |
| <a href="https://logging.apache.org/log4j/2.x/apidocs/org/apache/logging/log4j/util/StringMap.html" title="class or interface in org.apache.logging.log4j.util" class="external-link">StringMap</a> reusable)</code></div> |
| <div class="col-last even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"> |
| <div class="block">Returns a <code>StringMap</code> object initialized with the specified properties and the appropriate |
| context data.</div> |
| </div> |
| <div class="col-first odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="https://logging.apache.org/log4j/2.x/apidocs/org/apache/logging/log4j/util/ReadOnlyStringMap.html" title="class or interface in org.apache.logging.log4j.util" class="external-link">ReadOnlyStringMap</a></code></div> |
| <div class="col-second odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"><code><a href="#rawContextData()" class="member-name-link">rawContextData</a>()</code></div> |
| <div class="col-last odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3"> |
| <div class="block">Returns a <code>ReadOnlyStringMap</code> object reflecting the current state of the context.</div> |
| </div> |
| </div> |
| </div> |
| </div> |
| </section> |
| </li> |
| </ul> |
| </section> |
| <section class="details"> |
| <ul class="details-list"> |
| <!-- ============ METHOD DETAIL ========== --> |
| <li> |
| <section class="method-details" id="method-detail"> |
| <h2>Method Details</h2> |
| <ul class="member-list"> |
| <li> |
| <section class="detail" id="injectContextData(java.util.List,org.apache.logging.log4j.util.StringMap)"> |
| <h3>injectContextData</h3> |
| <div class="member-signature"><span class="return-type"><a href="https://logging.apache.org/log4j/2.x/apidocs/org/apache/logging/log4j/util/StringMap.html" title="class or interface in org.apache.logging.log4j.util" class="external-link">StringMap</a></span> <span class="element-name">injectContextData</span><wbr><span class="parameters">(<a href="https://docs.oracle.com/javase/8/docs/api/java/util/List.html" title="class or interface in java.util" class="external-link">List</a><<a href="config/Property.html" title="class in org.apache.logging.log4j.core.config">Property</a>> properties, |
| <a href="https://logging.apache.org/log4j/2.x/apidocs/org/apache/logging/log4j/util/StringMap.html" title="class or interface in org.apache.logging.log4j.util" class="external-link">StringMap</a> reusable)</span></div> |
| <div class="block">Returns a <code>StringMap</code> object initialized with the specified properties and the appropriate |
| context data. The returned value may be the specified parameter or a different object. |
| <p> |
| This method will be called for each log event to initialize its context data and implementors should take |
| care to make this method as performant as possible while preserving at least the following thread-safety |
| guarantee. |
| </p><p> |
| Thread-safety note: The returned object can safely be passed off to another thread: future changes in the |
| underlying context data will not be reflected in the returned object. |
| </p><p> |
| Example implementation: |
| </p> |
| <pre> |
| public StringMap injectContextData(List<Property> properties, StringMap reusable) { |
| if (properties == null || properties.isEmpty()) { |
| // assume context data is stored in a copy-on-write data structure that is safe to pass to another thread |
| return (StringMap) rawContextData(); |
| } |
| // first copy configuration properties into the result |
| ThreadContextDataInjector.copyProperties(properties, reusable); |
| |
| // then copy context data key-value pairs (may overwrite configuration properties) |
| reusable.putAll(rawContextData()); |
| return reusable; |
| } |
| </pre></div> |
| <dl class="notes"> |
| <dt>Parameters:</dt> |
| <dd><code>properties</code> - Properties from the log4j configuration to be added to the resulting ReadOnlyStringMap. May be |
| <code>null</code> or empty</dd> |
| <dd><code>reusable</code> - a <code>StringMap</code> instance that may be reused to avoid creating temporary objects</dd> |
| <dt>Returns:</dt> |
| <dd>a <code>StringMap</code> instance initialized with the specified properties and the appropriate |
| context data. The returned value may be the specified parameter or a different object.</dd> |
| <dt>See Also:</dt> |
| <dd> |
| <ul class="see-list-long"> |
| <li><a href="impl/ThreadContextDataInjector.html#copyProperties(java.util.List,org.apache.logging.log4j.util.StringMap)"><code>ThreadContextDataInjector.copyProperties(List, StringMap)</code></a></li> |
| </ul> |
| </dd> |
| </dl> |
| </section> |
| </li> |
| <li> |
| <section class="detail" id="rawContextData()"> |
| <h3>rawContextData</h3> |
| <div class="member-signature"><span class="return-type"><a href="https://logging.apache.org/log4j/2.x/apidocs/org/apache/logging/log4j/util/ReadOnlyStringMap.html" title="class or interface in org.apache.logging.log4j.util" class="external-link">ReadOnlyStringMap</a></span> <span class="element-name">rawContextData</span>()</div> |
| <div class="block">Returns a <code>ReadOnlyStringMap</code> object reflecting the current state of the context. Configuration properties |
| are not included in the result. |
| <p> |
| This method may be called multiple times for each log event by Filters and Lookups and implementors should take |
| care to make this method as performant as possible while preserving at least the following thread-safety |
| guarantee. |
| </p><p> |
| Thread-safety note: The returned object can only be safely used <em>in the current thread</em>. Changes in the |
| underlying context may or may not be reflected in the returned object, depending on the context data source and |
| the implementation of this method. It is not safe to pass the returned object to another thread. |
| </p></div> |
| <dl class="notes"> |
| <dt>Returns:</dt> |
| <dd>a <code>ReadOnlyStringMap</code> object reflecting the current state of the context, may not return <code>null</code></dd> |
| </dl> |
| </section> |
| </li> |
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