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Support 'unless' expression for cache veto

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Allow @Cachable, @CachePut and equivalent XML configuration to provide
a SpEL expression that can be used to veto putting an item into the
cache. Unlike 'condition' the 'unless' parameter is evaluated after
the method has been called and can therefore reference the #result.

For example:

    @Cacheable(value="book",
        condition="#name.length < 32",
        unless="#result.hardback")

This commit also allows #result to be referenced from @CacheEvict
expressions as long as 'beforeInvocation' is false.

Issue: SPR-8871
This commit is contained in:
Phillip Webb
2013-01-24 17:16:29 -08:00
parent 3252cb5a0f
commit 8c2ace33cb
22 changed files with 385 additions and 106 deletions
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14
src/reference/docbook/cache.xml
View File

@@ -152,6 +152,13 @@ public Book findBook(ISBN isbn, boolean checkWarehouse, boolean includeUsed)</pr
<programlisting language="java"><![CDATA[@Cacheable(value="book", condition="#name.length < 32")
public Book findBook(String name)]]></programlisting>
<para>In addition the <literal>conditional</literal> parameter, the <literal>unless</literal> parameter can be used to veto the adding of a value to the cache. Unlike
<literal>conditional</literal>, <literal>unless</literal> <literal>SpEL</literal> expressions are evalulated <emphasis>after</emphasis> the method has been called. Expanding
on the previous example - perhaps we only want to cache paperback books:</para>
<programlisting language="java"><![CDATA[@Cacheable(value="book", condition="#name.length < 32", unless="#result.hardback")
public Book findBook(String name)]]></programlisting>
</section>
<section xml:id="cache-spel-context">
@@ -218,6 +225,13 @@ public Book findBook(String name)]]></programlisting>
<emphasis><![CDATA[#arg]]></emphasis> stands for the argument index (starting from 0).</entry>
<entry><screen>iban</screen> or <screen>a0</screen> (one can also use <screen>p0</screen> or <literal><![CDATA[p<#arg>]]></literal> notation as an alias).</entry>
</row>
<row>
<entry>result</entry>
<entry>evaluation context</entry>
<entry>The result of the method call (the value to be cached). Only available in '<literal>unless</literal>' expressions and '<literal>cache evict</literal>'
expression (when <literal>beforeInvocation</literal> is <literal>false</literal>).</entry>
<entry><screen>#result</screen></entry>
</row>
</tbody>
</tgroup>
</table>