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| <div class="sub-title"><span class="module-label-in-type">Module</span> <a href="../../../../module-summary.html">openj9.sharedclasses</a></div> |
| <div class="sub-title"><span class="package-label-in-type">Package</span> <a href="package-summary.html">com.ibm.oti.shared</a></div> |
| <h1 title="Interface SharedDataHelper" class="title">Interface SharedDataHelper</h1> |
| </div> |
| <section class="description"> |
| <dl class="notes"> |
| <dt>All Superinterfaces:</dt> |
| <dd><code><a href="SharedHelper.html" title="interface in com.ibm.oti.shared">SharedHelper</a></code></dd> |
| </dl> |
| <hr> |
| <div class="type-signature"><span class="modifiers">public interface </span><span class="element-name type-name-label">SharedDataHelper</span><span class="extends-implements"> |
| extends <a href="SharedHelper.html" title="interface in com.ibm.oti.shared">SharedHelper</a></span></div> |
| <div class="block"><p>SharedDataHelper API that stores and finds byte data using String tokens.</p> |
| <h2>Description</h2> |
| <p>A SharedDataHelper is obtained by calling getSharedDataHelper(ClassLoader) on a SharedDataHelperFactory.</p> |
| <p>The SharedDataHelper allows byte data to be written into the shared class cache and shared with other VMs.</p> |
| <p>Byte data to be stored in the cache should exist in a java.nio.ByteBuffer which is copied to the cache when |
| storeSharedData() is called. The function returns a read-only java.nio.ByteBuffer which is the shared copy of the data. |
| Any subsequent changes to the ByteBuffer are therefore not reflected in the cache unless it is re-stored.</p> |
| <p>Byte data is found in the cache by calling findSharedData() which returns a read-only java.nio.ByteBuffer which |
| maps to the byte data that exists in the cache.</p> |
| <h2>Tokens</h2> |
| <p>A String token is chosen/generated by the application which is using the Helper and should ideally include a unique |
| identifier and some kind of versioning information. Eg. com.foo.myApp31_myDoozerData_003. The important factor is that |
| other VMs running the same application should be able to apply the same algorithm and find the data. </p> |
| <h2>Dynamic Cache Updates</h2> |
| <p>Since the shared cache is persistent beyond the lifetime of a JVM, data in the shared cache may become out-of-date (<q>stale</q>). |
| Using this helper, it is entirely the responsibility of the application to ensure that cache entries are kept up-to-date. |
| Tokens have no meaning to the cache, so effectively turn it into a dictionary of classes.</p> |
| <p>Eg. A token may be the location where the class was found, combined with some type of versioning data.</p> |
| <p>If an application stores multiple versions of the same data using the same token, only the most recent will be returned by findSharedData.</p></div> |
| <dl class="notes"> |
| <dt>See Also:</dt> |
| <dd><a href="SharedHelper.html" title="interface in com.ibm.oti.shared"><code>SharedHelper</code></a>, |
| <a href="SharedDataHelperFactory.html" title="interface in com.ibm.oti.shared"><code>SharedDataHelperFactory</code></a>, |
| <a href="SharedClassPermission.html" title="class in com.ibm.oti.shared"><code>SharedClassPermission</code></a></dd> |
| </dl> |
| </section> |
| <section class="summary"> |
| <ul class="summary-list"> |
| <!-- ========== METHOD SUMMARY =========== --> |
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| <section class="method-summary" id="method.summary"> |
| <h2>Method Summary</h2> |
| <div id="method-summary-table"> |
| <div class="table-tabs" role="tablist" aria-orientation="horizontal"><button id="method-summary-table-tab0" role="tab" aria-selected="true" aria-controls="method-summary-table.tabpanel" tabindex="0" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table', 3)" class="active-table-tab">All Methods</button><button id="method-summary-table-tab2" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab2', 3)" class="table-tab">Instance Methods</button><button id="method-summary-table-tab3" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab3', 3)" class="table-tab">Abstract Methods</button></div> |
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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-tab2 method-summary-table method-summary-table-tab3"><code><a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/nio/ByteBuffer.html" title="class or interface in java.nio" class="external-link" target="_blank">ByteBuffer</a></code></div> |
| <div class="col-second even-row-color method-summary-table-tab2 method-summary-table method-summary-table-tab3"><code><span class="member-name-link"><a href="#findSharedData(java.lang.String)">findSharedData</a></span>​(<a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link" target="_blank">String</a> token)</code></div> |
| <div class="col-last even-row-color method-summary-table-tab2 method-summary-table method-summary-table-tab3"> |
| <div class="block">Find data in the shared cache using a specific token.</div> |
| </div> |
| <div class="col-first odd-row-color method-summary-table-tab2 method-summary-table method-summary-table-tab3"><code><a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/nio/ByteBuffer.html" title="class or interface in java.nio" class="external-link" target="_blank">ByteBuffer</a></code></div> |
| <div class="col-second odd-row-color method-summary-table-tab2 method-summary-table method-summary-table-tab3"><code><span class="member-name-link"><a href="#storeSharedData(java.lang.String,java.nio.ByteBuffer)">storeSharedData</a></span>​(<a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link" target="_blank">String</a> token, |
| <a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/nio/ByteBuffer.html" title="class or interface in java.nio" class="external-link" target="_blank">ByteBuffer</a> data)</code></div> |
| <div class="col-last odd-row-color method-summary-table-tab2 method-summary-table method-summary-table-tab3"> |
| <div class="block">Store data in the shared cache using a specific token.</div> |
| </div> |
| </div> |
| </div> |
| </div> |
| <div class="inherited-list"> |
| <h3 id="methods.inherited.from.class.com.ibm.oti.shared.SharedHelper">Methods declared in interface com.ibm.oti.shared.<a href="SharedHelper.html" title="interface in com.ibm.oti.shared">SharedHelper</a></h3> |
| <code><a href="SharedHelper.html#getClassLoader()">getClassLoader</a></code></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="findSharedData(java.lang.String)"> |
| <h3>findSharedData</h3> |
| <div class="member-signature"><span class="return-type"><a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/nio/ByteBuffer.html" title="class or interface in java.nio" class="external-link" target="_blank">ByteBuffer</a></span> <span class="element-name">findSharedData</span>​<span class="parameters">(<a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link" target="_blank">String</a> token)</span></div> |
| <div class="block">Find data in the shared cache using a specific token.<p> |
| Data will be returned only for an exact String match of the token. Otherwise, null is returned.<br> |
| The ByteBuffer returned is read-only and cannot be modified.<br> |
| If a SecurityManager is installed, findSharedData can only be called by code whose caller-classloader |
| has been granted <q>read</q> permissions to the shared class cache. |
| <p></div> |
| <dl class="notes"> |
| <dt>Parameters:</dt> |
| <dd><code>token</code> - String. |
| A String token to be used as a key</dd> |
| <dt>Returns:</dt> |
| <dd>ByteBuffer. |
| A read-only ByteBuffer containing the cached data, or null.</dd> |
| </dl> |
| </section> |
| </li> |
| <li> |
| <section class="detail" id="storeSharedData(java.lang.String,java.nio.ByteBuffer)"> |
| <h3>storeSharedData</h3> |
| <div class="member-signature"><span class="return-type"><a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/nio/ByteBuffer.html" title="class or interface in java.nio" class="external-link" target="_blank">ByteBuffer</a></span> <span class="element-name">storeSharedData</span>​<span class="parameters">(<a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link" target="_blank">String</a> token, |
| <a href="https://docs.oracle.com/en/java/javase/16/docs/api/java.base/java/nio/ByteBuffer.html" title="class or interface in java.nio" class="external-link" target="_blank">ByteBuffer</a> data)</span></div> |
| <div class="block">Store data in the shared cache using a specific token.<p> |
| If the data is stored successfully, the shared read-only copy of the data is returned. Otherwise, null is returned.<br> |
| If data already exists for the token specified, the old data is marked <q>stale</q> in the cache and is replaced by the new data.<br> |
| If the exact same data already exists in the cache under the same token, the data is not duplicated and the cached version is returned.<br> |
| If null is passed as the data argument, the data currently stored against that token is marked "stale" and null is returned.<br> |
| If a SecurityManager is installed, storeSharedData can only be called by code whose caller-classloader |
| has been granted <q>write</q> permissions to the shared class cache. |
| <p></div> |
| <dl class="notes"> |
| <dt>Parameters:</dt> |
| <dd><code>token</code> - String. |
| A String token to be used as a key</dd> |
| <dd><code>data</code> - ByteBuffer. |
| A ByteBuffer of data to copy to the cache</dd> |
| <dt>Returns:</dt> |
| <dd>ByteBuffer. |
| A read-only ByteBuffer containing the cached data, or null.</dd> |
| </dl> |
| </section> |
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