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Posted to commits@aries.apache.org by bu...@apache.org on 2016/05/20 15:20:54 UTC
svn commit: r988745 - in /websites/staging/aries/trunk/content: ./
modules/transactioncontrol.html modules/tx-control/quickstart.html
modules/tx-control/spring-tx.html
Author: buildbot
Date: Fri May 20 15:20:54 2016
New Revision: 988745
Log:
Staging update by buildbot for aries
Added:
websites/staging/aries/trunk/content/modules/tx-control/spring-tx.html
Modified:
websites/staging/aries/trunk/content/ (props changed)
websites/staging/aries/trunk/content/modules/transactioncontrol.html
websites/staging/aries/trunk/content/modules/tx-control/quickstart.html
Propchange: websites/staging/aries/trunk/content/
------------------------------------------------------------------------------
--- cms:source-revision (original)
+++ cms:source-revision Fri May 20 15:20:54 2016
@@ -1 +1 @@
-1744547
+1744756
Modified: websites/staging/aries/trunk/content/modules/transactioncontrol.html
==============================================================================
--- websites/staging/aries/trunk/content/modules/transactioncontrol.html (original)
+++ websites/staging/aries/trunk/content/modules/transactioncontrol.html Fri May 20 15:20:54 2016
@@ -287,12 +287,16 @@ to its official release. Also the behavi
latest wording in the RFC. The project maintainers will, however try to keep pace with the RFC, and to
ensure that the implementations are compliant with any OSGi specifications that result from the RFC.</p>
<h1 id="getting-started">Getting started<a class="headerlink" href="#getting-started" title="Permanent link">¶</a></h1>
-<p>If you're new to the Transaction Control service then we recommend that you read the <a href="tx-control/quickstart.html">quickstart documentation first</a>.</p>
+<p>If you're new to the Transaction Control service then we recommend that you read the
+<a href="tx-control/quickstart.html">quickstart documentation first</a>.</p>
<p>More detailed documentation is available in the <a href="tx-control/index.html">Aries Transaction Control Project</a></p>
<h2 id="why-use-the-transaction-control-service">Why use the Transaction Control service?<a class="headerlink" href="#why-use-the-transaction-control-service" title="Permanent link">¶</a></h2>
<p>Simply put the Transaction Control service makes resource access easy! There's no need to worry about
transaction lifecycle or closing connections, and there's built in support for useful features like
connection pooling.</p>
+<p>In addition to being simple the Transaction Control service also makes transaction management explicit. As a
+result it is easier to follow the transactions flowing throughout your code, and it protects you from the
+<a href="tx-control/spring-tx.html">proxy problem</a> that declarative transaction strategies often suffer from.</p>
<h2 id="modules">Modules<a class="headerlink" href="#modules" title="Permanent link">¶</a></h2>
<p>The following modules are available for use in OSGi</p>
<ol>
Modified: websites/staging/aries/trunk/content/modules/tx-control/quickstart.html
==============================================================================
--- websites/staging/aries/trunk/content/modules/tx-control/quickstart.html (original)
+++ websites/staging/aries/trunk/content/modules/tx-control/quickstart.html Fri May 20 15:20:54 2016
@@ -330,7 +330,8 @@ automatically committed or rolled back u
<em>Transactional</em> scope has been started. The <code>supports</code> and <code>notSupported</code>
methods can be used to ensure that a <em>No Transaction</em> scope has been started.</p>
<p>Simple scope management is perfect in most situations, but you may also wish to read about
-<a href="advancedScopes.html">more advanced scope control techniques</a> or <a href="exceptionManagement.html">exception management</a> once you've mastered the basics.</p>
+<a href="advancedScopes.html">more advanced scope control techniques</a> or <a href="exceptionManagement.html">exception management</a> once you've mastered the basics.
+There are also some things to consider if you're <a href="spring-tx.html">migrating from Spring or Java EE</a>.</p>
<h2 id="accessing-resources">Accessing Resources<a class="headerlink" href="#accessing-resources" title="Permanent link">¶</a></h2>
<p>A <code>ResourceProvider</code> is a generic factory for scoped resources. Typically you will use a more
specific interface for type safety. For example the Transaction Control specification defines
Added: websites/staging/aries/trunk/content/modules/tx-control/spring-tx.html
==============================================================================
--- websites/staging/aries/trunk/content/modules/tx-control/spring-tx.html (added)
+++ websites/staging/aries/trunk/content/modules/tx-control/spring-tx.html Fri May 20 15:20:54 2016
@@ -0,0 +1,506 @@
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+<h1 id="migrating-from-declarative-transactions">Migrating from declarative transactions<a class="headerlink" href="#migrating-from-declarative-transactions" title="Permanent link">¶</a></h1>
+<p>Many popular application containers, such as Spring or Java EE, offer declarative transaction management.
+Specifically, the container offers a model where transaction boundaries are defined using metadata, usually as
+annotations on public methods.</p>
+<h2 id="the-basics">The Basics<a class="headerlink" href="#the-basics" title="Permanent link">¶</a></h2>
+<p>A typical transactional method in a declarative model might look like this:</p>
+<div class="codehilite"><pre><span class="p">@</span><span class="n">Transactional</span>
+<span class="n">public</span> <span class="n">Long</span> <span class="n">getCustomerId</span><span class="p">(</span><span class="n">String</span> <span class="n">email</span><span class="p">)</span> <span class="p">{</span>
+ <span class="o">//</span> <span class="n">Some</span> <span class="n">business</span> <span class="n">logic</span> <span class="n">in</span> <span class="n">here</span><span class="p">...</span>
+<span class="p">}</span>
+</pre></div>
+
+
+<p>Using Transaction control the same thing would look like:</p>
+<div class="codehilite"><pre><span class="n">public</span> <span class="n">Long</span> <span class="n">getCustomerId</span><span class="p">(</span><span class="n">String</span> <span class="n">email</span><span class="p">)</span> <span class="p">{</span>
+ <span class="n">txControl</span><span class="p">.</span><span class="n">required</span><span class="p">(()</span> <span class="o">-></span> <span class="p">{</span>
+ <span class="o">//</span> <span class="n">Some</span> <span class="n">business</span> <span class="n">logic</span> <span class="n">in</span> <span class="n">here</span><span class="p">...</span>
+ <span class="p">});</span>
+<span class="p">}</span>
+</pre></div>
+
+
+<p>The main change is that the transactions have moved from being metadata defined, and started by the container,
+to being code defined and started by the Transaction Control service. This gives several significant advantages.</p>
+<h2 id="the-scoping-problem">The Scoping Problem<a class="headerlink" href="#the-scoping-problem" title="Permanent link">¶</a></h2>
+<p>When using method-level metadata to define transaction boundaries it is not possible to manage transactions
+on a finer level. This makes it difficult to suspend or nest transactions unless you create a new method to hold
+the extra logic.</p>
+<h3 id="a-simple-example">A Simple Example<a class="headerlink" href="#a-simple-example" title="Permanent link">¶</a></h3>
+<p>If we want to write an audit message it usually needs to occur in a new transaction, as typically it should persist
+even if the overall action fails. In a declarative model this requires a separate method with a new boundary,
+even if the audit function is a private implementation detail of the Object.</p>
+<div class="codehilite"><pre><span class="p">@</span><span class="n">Transactional</span>
+<span class="n">public</span> <span class="n">void</span> <span class="n">changePassword</span><span class="p">(</span><span class="n">String</span> <span class="n">email</span><span class="p">,</span> <span class="n">String</span> <span class="n">password</span><span class="p">)</span> <span class="p">{</span>
+
+ <span class="n">auditPasswordChangeAttempt</span><span class="p">(</span><span class="n">email</span><span class="p">);</span>
+
+ <span class="o">//</span> <span class="n">Some</span> <span class="n">business</span> <span class="n">logic</span> <span class="n">in</span> <span class="n">here</span><span class="p">...</span>
+<span class="p">}</span>
+
+<span class="p">@</span><span class="n">Transactional</span><span class="p">(</span><span class="n">REQUIRES_NEW</span><span class="p">)</span>
+<span class="n">public</span> <span class="n">void</span> <span class="n">auditPasswordChangeAttempt</span><span class="p">(</span><span class="n">String</span> <span class="n">email</span><span class="p">)</span> <span class="p">{</span>
+ <span class="o">//</span> <span class="n">One</span> <span class="n">line</span> <span class="n">to</span> <span class="n">write</span> <span class="n">the</span> <span class="n">audit</span> <span class="n">message</span>
+<span class="p">}</span>
+</pre></div>
+
+
+<p>With transaction control there is no need to create a method just for the internal audit function.</p>
+<p>@Transactional
+ public void changePassword(String email, String password) {</p>
+<div class="codehilite"><pre> <span class="n">txControl</span><span class="p">.</span><span class="n">required</span><span class="p">(()</span> <span class="o">-></span> <span class="p">{</span>
+
+ <span class="n">txControl</span><span class="p">.</span><span class="n">requiresNew</span><span class="p">(()</span> <span class="o">-></span> <span class="p">{</span>
+ <span class="o">//</span> <span class="n">One</span> <span class="n">line</span> <span class="n">to</span> <span class="n">write</span> <span class="n">the</span> <span class="n">audit</span> <span class="n">message</span>
+ <span class="p">});</span>
+
+ <span class="o">//</span> <span class="n">Some</span> <span class="n">business</span> <span class="n">logic</span> <span class="n">in</span> <span class="n">here</span><span class="p">...</span>
+ <span class="p">});</span>
+<span class="p">}</span>
+</pre></div>
+
+
+<h2 id="the-proxy-problem">The Proxy Problem<a class="headerlink" href="#the-proxy-problem" title="Permanent link">¶</a></h2>
+<p>The Proxy problem is a rather insidious issue that affects declarative transactions, and it is a result of how they
+are implemented. If bytecode weaving is used to directly add transactional behaviour to an object then it will
+always work the same way. Most solutions, however, do not use bytecode weaving, but instead use a proxy
+pattern. When a call is made on the proxy the proxy will perform any necessary transaction management
+before and after delegating the call to the real object. This works well, except if the object makes any internal
+method calls.</p>
+<p>In the general case proxying is unsafe because you cannot rely on a method's metadata to decide what
+transaction state will exist when it is called!</p>
+<h3 id="examples-of-the-proxy-problem">Examples of the Proxy Problem<a class="headerlink" href="#examples-of-the-proxy-problem" title="Permanent link">¶</a></h3>
+<p>The following examples are all based on real code migrated from Spring to Transaction Control.</p>
+<h4 id="a-simple-example_1">A Simple Example<a class="headerlink" href="#a-simple-example_1" title="Permanent link">¶</a></h4>
+<div class="codehilite"><pre><span class="n">AbstractPersistenceDataManagerImpl</span> <span class="p">{</span>
+
+ <span class="p">@</span><span class="n">Transactional</span><span class="p">(</span><span class="n">propagation</span> <span class="p">=</span> <span class="n">SUPPORTS</span><span class="p">,</span> <span class="n">readOnly</span> <span class="p">=</span> <span class="n">true</span><span class="p">)</span>
+ <span class="n">public</span> <span class="o"><</span><span class="n">T</span><span class="o">></span> <span class="n">T</span> <span class="n">search</span><span class="p">(</span><span class="n">Class</span><span class="o"><</span><span class="n">T</span><span class="o">></span> <span class="n">entityClass</span><span class="p">,</span> <span class="n">Object</span> <span class="n">pk</span><span class="p">,</span> <span class="n">Object</span> <span class="n">params</span><span class="p">)</span> <span class="p">{</span>
+ <span class="k">return</span> <span class="p">(</span><span class="n">T</span><span class="p">)</span> <span class="nb">find</span><span class="p">(</span><span class="n">entityClass</span><span class="p">,</span> <span class="n">pk</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="p">}</span>
+
+ <span class="p">@</span><span class="n">Transactional</span><span class="p">(</span><span class="n">readOnly</span> <span class="p">=</span> <span class="n">true</span><span class="p">)</span>
+ <span class="n">public</span> <span class="n">UniWorksSuperDBEntity</span> <span class="nb">find</span><span class="p">(</span><span class="n">Class</span> <span class="n">entityClass</span><span class="p">,</span> <span class="n">Object</span> <span class="n">pk</span><span class="p">,</span> <span class="n">Object</span> <span class="n">params</span><span class="p">)</span> <span class="p">{</span>
+ <span class="k">return</span> <span class="p">(</span><span class="n">UniWorksSuperDBEntity</span><span class="p">)</span> <span class="n">em</span><span class="p">.</span><span class="nb">find</span><span class="p">(</span><span class="n">entityClass</span><span class="p">,</span> <span class="n">pk</span><span class="p">);</span>
+ <span class="p">}</span>
+<span class="p">}</span>
+</pre></div>
+
+
+<p>In this case the <code>search</code> method does not require a transaction, but delegates to the
+<code>find</code> method which does. If proxying is used then the <code>find</code> method will
+sometimes run in a transaction and sometimes not. On the other hand, if weaving is used then the
+<code>find</code> method will <em>always</em> run under a transaction This may seem innocuous, but it
+can cause big problems. We always want to be certain about where a transaction will start and stop!</p>
+<h4 id="extending-the-simple-example">Extending the Simple Example<a class="headerlink" href="#extending-the-simple-example" title="Permanent link">¶</a></h4>
+<p>The following type is part of the same project as the previous example, and interacts with it.</p>
+<div class="codehilite"><pre><span class="n">AbstractDataManager</span> <span class="p">{</span>
+
+ <span class="p">@</span><span class="n">Transactional</span><span class="p">(</span><span class="n">propagation</span> <span class="p">=</span> <span class="n">NOT_SUPPORTED</span><span class="p">,</span> <span class="n">readOnly</span> <span class="p">=</span> <span class="n">true</span><span class="p">)</span>
+ <span class="n">public</span> <span class="n">UniWorksSuperDTO</span> <span class="n">search</span><span class="p">(</span><span class="n">Object</span> <span class="n">pk</span><span class="p">,</span> <span class="n">Object</span> <span class="n">params</span><span class="p">)</span> <span class="p">{</span>
+
+ <span class="n">UniWorksSuperDBEntity</span> <span class="n">entity</span> <span class="p">=</span> <span class="n">persistenceDataManager</span>
+ <span class="p">.</span><span class="n">search</span><span class="p">(</span><span class="n">getEntityClass</span><span class="p">(),</span> <span class="n">createNewPKFromDTOPK</span><span class="p">(</span><span class="n">pk</span><span class="p">),</span> <span class="n">null</span><span class="p">);</span>
+
+ <span class="n">loadLinkedTablesTop</span><span class="p">(</span><span class="n">entity</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="p">}</span>
+
+ <span class="n">protected</span> <span class="n">final</span> <span class="n">void</span> <span class="n">loadLinkedTablesTop</span><span class="p">(</span><span class="n">UniWorksSuperDBEntity</span> <span class="n">entity</span><span class="p">,</span> <span class="n">Object</span> <span class="n">params</span><span class="p">)</span> <span class="p">{</span>
+ <span class="n">loadLinkedTables</span><span class="p">(</span><span class="n">entity</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="p">}</span>
+
+ <span class="p">@</span><span class="n">Transactional</span><span class="p">(</span><span class="n">readOnly</span> <span class="p">=</span> <span class="n">true</span><span class="p">)</span>
+ <span class="n">public</span> <span class="n">void</span> <span class="n">loadLinkedTables</span><span class="p">(</span><span class="n">UniWorksSuperDBEntity</span> <span class="n">entity</span><span class="p">,</span> <span class="n">Object</span> <span class="n">params</span><span class="p">)</span> <span class="p">{</span>
+ <span class="n">loadLinkedTablesGenerated</span><span class="p">(</span><span class="n">entity</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="n">loadLinkedTransients</span><span class="p">(</span><span class="n">entity</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="p">}</span>
+<span class="p">}</span>
+</pre></div>
+
+
+<p>Now lets imagine that a call comes in to the <code>search</code> method of this class from some client.</p>
+<h5 id="proxied">Proxied<a class="headerlink" href="#proxied" title="Permanent link">¶</a></h5>
+<ol>
+<li>The container proxy for the data manager halts any ongoing transaction due to the
+<code>NOT_SUPPORTED</code> metadata, entering an undefined scope.</li>
+<li>The code calls search on the persistenceDataManager</li>
+<li>The container proxy for the persistence data manager does not start or stop a transaction due to the
+<code>SUPPORTS</code> scope.</li>
+<li>The code calls <code>find</code> on the persistenceDataManager, but without touching the proxy.</li>
+<li>The code accesses the entity outside a transaction</li>
+<li>The code returns the entity, and no transaction change is necessary</li>
+<li>The code calls loadLinkedTablesTop, which calls loadLinkedTables. No proxy is touched therefore no
+transaction is started.</li>
+<li>The Tables are populated with data from the entity. Lazy loading is possible as the entity is still attached.</li>
+</ol>
+<h5 id="woven">Woven<a class="headerlink" href="#woven" title="Permanent link">¶</a></h5>
+<ol>
+<li>The weaving code for the data manager halts any ongoing transaction due to the
+<code>NOT_SUPPORTED</code> metadata, entering an undefined scope.</li>
+<li>The code calls search on the persistenceDataManager</li>
+<li>The weaving code for the persistence data manager does not start or stop a transaction due to the
+<code>SUPPORTS</code> scope.</li>
+<li>The code calls <code>find</code> on the persistenceDataManager, at this point the weaving code starts
+a transaction.</li>
+<li>The code accesses the entity inside the transaction</li>
+<li>The code returns the entity, and the transaction completes. This detaches the entity and prevents lazy loading.</li>
+<li>The code calls loadLinkedTablesTop, which calls loadLinkedTables. The weaving code starts a new
+transaction.</li>
+<li>The Code fails as the entity is not able to access its lazily loaded data.</li>
+</ol>
+<h3 id="strategies-for-managing-transaction-states">Strategies for Managing Transaction States<a class="headerlink" href="#strategies-for-managing-transaction-states" title="Permanent link">¶</a></h3>
+<p>Ensuring consistency is vital when writing code that uses transactions. It is therefore usually a good idea to
+ensure that any reused code is captured in a private method, and that it asserts the correct transaction state
+before it begins.</p>
+<div class="codehilite"><pre><span class="n">AbstractDataManager</span> <span class="p">{</span>
+
+ <span class="n">public</span> <span class="n">UniWorksSuperDTO</span> <span class="n">search</span><span class="p">(</span><span class="n">Object</span> <span class="n">pk</span><span class="p">,</span> <span class="n">Object</span> <span class="n">params</span><span class="p">)</span> <span class="p">{</span>
+
+ <span class="n">txControl</span><span class="p">.</span><span class="n">build</span><span class="p">().</span><span class="n">readOnly</span><span class="p">().</span><span class="n">notSupported</span><span class="p">(()</span> <span class="o">-></span> <span class="p">{</span>
+ <span class="n">UniWorksSuperDBEntity</span> <span class="n">entity</span> <span class="p">=</span> <span class="n">persistenceDataManager</span>
+ <span class="p">.</span><span class="n">search</span><span class="p">(</span><span class="n">getEntityClass</span><span class="p">(),</span> <span class="n">createNewPKFromDTOPK</span><span class="p">(</span><span class="n">pk</span><span class="p">),</span> <span class="n">null</span><span class="p">);</span>
+
+ <span class="n">loadLinkedTablesTop</span><span class="p">(</span><span class="n">entity</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="k">return</span> <span class="n">entity</span><span class="p">;</span>
+ <span class="p">}</span>
+ <span class="p">}</span>
+
+ <span class="n">protected</span> <span class="n">final</span> <span class="n">void</span> <span class="n">loadLinkedTablesTop</span><span class="p">(</span><span class="n">UniWorksSuperDBEntity</span> <span class="n">entity</span><span class="p">,</span> <span class="n">Object</span> <span class="n">params</span><span class="p">)</span> <span class="p">{</span>
+ <span class="n">loadLinkedTables</span><span class="p">(</span><span class="n">entity</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="p">}</span>
+
+ <span class="n">public</span> <span class="n">void</span> <span class="n">loadLinkedTables</span><span class="p">(</span><span class="n">UniWorksSuperDBEntity</span> <span class="n">entity</span><span class="p">,</span> <span class="n">Object</span> <span class="n">params</span><span class="p">)</span> <span class="p">{</span>
+ <span class="n">txControl</span><span class="p">.</span><span class="n">build</span><span class="p">().</span><span class="n">readOnly</span><span class="p">().</span><span class="n">required</span><span class="p">(()</span> <span class="o">-></span> <span class="p">{</span>
+ <span class="n">loadLinkedTables</span><span class="p">(</span><span class="n">entity</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="p">});</span>
+ <span class="p">}</span>
+
+ <span class="o">/**</span>
+ <span class="o">*</span> <span class="n">This</span> <span class="n">method</span> <span class="n">does</span> <span class="n">not</span> <span class="n">need</span> <span class="n">a</span> <span class="n">transaction</span><span class="p">,</span> <span class="n">but</span> <span class="n">does</span> <span class="n">need</span> <span class="n">a</span> <span class="n">scope</span>
+ <span class="o">*/</span>
+ <span class="n">private</span> <span class="n">void</span> <span class="n">loadLinkedTablesInternal</span><span class="p">(</span><span class="n">UniWorksSuperDBEntity</span> <span class="n">entity</span><span class="p">,</span> <span class="n">Object</span> <span class="n">params</span><span class="p">)</span> <span class="p">{</span>
+ <span class="n">assert</span> <span class="n">txControl</span><span class="p">.</span><span class="n">activeScope</span><span class="p">();</span>
+
+ <span class="n">loadLinkedTablesGenerated</span><span class="p">(</span><span class="n">entity</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="n">loadLinkedTransients</span><span class="p">(</span><span class="n">entity</span><span class="p">,</span> <span class="n">params</span><span class="p">);</span>
+ <span class="p">}</span>
+<span class="p">}</span>
+</pre></div>
+
+
+<p>Writing code in this way ensures that even when a mixture of transactional and non transactional actions are
+needed, there will always be a consistent expectation of the transaction scope in each method.</p>
+<h2 id="exception-management">Exception management<a class="headerlink" href="#exception-management" title="Permanent link">¶</a></h2>
+<p>The final significant difference between declarative models and the Transaction Control Service is in how much
+work your application code needs to do when managing exceptions. More detail about managing exceptions
+<a href="exceptionManagement.html">is available here</a>.</p></div>
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