faq.fml

jsr170接口的java实现。是个apache的开源项目。

    <faq id="whats-pm">
      <question>
        What is a persistence manager?
      </question>
      <answer>
        <p>
          A persistence manager (PM) is an <em>internal</em> Jackrabbit
          component that handles the persistent storage of content nodes
          and properties. Each workspace of a Jackrabbit content repository
          uses a separate persistence manager to store the content in that
          workspace. Also the Jackrabbit version handler uses a separate
          persistence manager.
        </p>
        <p>
          The persistence manager sits at the very bottom layer of the
          Jackrabbit system architecture. Reliability, integrity and
          performance of the PM are <em>crucial</em> to the overall
          stability and performance of the repository. If e.g. the data
          that a PM is based upon is allowed to change through external
          means the integrity of the repository would be at risk
          (think of referential integrity / node references e.g.).
        </p>
        <p>
          In practice, a persistence manager is any Java class that
          implements the PersistenceManager <!-- TODO: add JavaDoc link -->
          interface and the associated behavioural contracts. Jackrabbit
          contains a set of built-in persistence manager classes that cover
          most of the deployment needs. There are also a few contributed
          persistence managers that give additional flexibility.
        </p>
      </answer>
    </faq>

    <faq id="whats-fs">
      <question>
        What is a Jackrabbit file system?
      </question>
      <answer>
        <p>
          A Jackrabbbit file system (FS) is an internal component that
          implements standard file system operations on top of some underlying
          storage mechanism (a normal file system, a database, a webdav server,
          or a custom file format). A file system component is any Java class
          that implements the FileSystem <!-- TODO: add JavaDoc link -->
          interface and the associated behavioural contracts. File systems
          are used in Jackrabbit both as subcomponents of the persistence
          managers and for general storage needs (for example to store the
          full text indexes).
        </p>
      </answer>
    </faq>

    <faq id="pm-abuse">
      <question>
        Can I use a persistence manager to access an existing data source?
      </question>
      <answer>
        <p>
          No. The persistence manager interface was never intended as being
          a general SPI that you could implement in order to integrate
          external data sources with proprietary formats (e.g. a customers
          database). The reason why we abstracted the PM interface was
          to leave room for future performance optimizations that would
          not affect the rest of the implementation (e.g. by storing the
          raw data in a b-tree based database instead of individual file).
        </p>
      </answer>
    </faq>

    <faq id="pm-smart">
      <question>
        How &quot;smart&quot; should a persistence manager be?
      </question>
      <answer>
        <p>
          A persistence manager should not be <em>intelligent</em>, i.e.
          it should not <em>interpret</em> the content it is managing.
          The only thing it should care about is to efficiently,
          consistently, and reliably store and read the content encapsulated
          in the passed NodeState and PropertyState objects. Though it
          might be feasible to write a custom persistence manager to
          represent existing legacy data in a level-1 (read-only) repository,
          I don't think the same is possible for a level-2 repository and
          I certainly would not recommend it.
        </p>
      </answer>
    </faq>

    <faq id="pm-available">
      <question>
        What persistence managers are available?
      </question>
      <answer>
        <p>
          The table below lists the currently available persistence managers,
          along with the status and pros and cons of each PM.
        </p>
        <table>
          <thead>
            <tr>
              <th>Persistence manager</th>
              <th>Status</th>
              <th>Pros</th>
              <th>Cons</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td>SimpleDbPersistenceManager (and subclasses thereof)</td>
              <td>mature</td>
              <td>
                <ul>
                  <li>Jackrabbit's default persistence manager</li>
                  <li>JDBC based persistence supporting a wide range of RDBMSs</li>
                  <li>zero-deployment, schema is automatically created</li>
                  <li>Transactional</li>
                </ul>
              </td>
              <td>
                <ul>
                  <li>uses simple non-normalized schema and binary serialization format which might not appeal to relational data modeling fans</li>
                </ul>
              </td>
            </tr>
            <tr>
              <td>BerkeleyDBPersistenceManager</td>
              <td>mature?</td>
              <td>
                <ul>
                  <li>btree-based persistence (BerkeleyDB JE)</li>
                  <li>zero-deployment</li>
                  <li>Transactional</li>
                </ul>
              </td>
              <td>
                <ul>
                  <li>Uses binary serialization format</li>
                  <li>Licensing issues</li>
                </ul>
              </td>
            </tr>
            <tr>
              <td>ObjectPersistenceManager</td>
              <td>mature</td>
              <td>
                <ul>
                  <li>File system based persistence</li>
                  <li>Easy to configure</li>
                </ul>
              </td>
              <td>
                <ul>
                  <li>Uses binary serialization format</li>
                  <li>If the JVM process is killed the repository might turn inconsistent</li>
                  <li>Not transactional</li>
                </ul>
              </td>
            </tr>
            <tr>
              <td>XMLPersistenceManager</td>
              <td>mature</td>
              <td>
                <ul>
                  <li>File system based persistence</li>
                  <li>Uses XML serialization format</li>
                  <li>Easy to configure</li>
                </ul>
              </td>
              <td>
                <ul>
                  <li>If the JVM process is killed the repository might turn inconsistent</li>
                  <li>Poor performance</li>
                  <li>Not transactional</li>
                </ul>
              </td>
            </tr>
            <tr>
              <td>ORM persistence manager</td>
              <td>experimental &amp; unfinished</td>
              <td>
                <ul>
                  <li>ORM-based persistence</li>
                  <li>Transactional</li>
                </ul>
              </td>
              <td>
                <ul>
                  <li>Complex to configure &amp; setup</li>
                  <li>Still being maintained?</li>
                </ul>
              </td>
            </tr>
          </tbody>
        </table>
      </answer>
    </faq>
  
    <faq id="fs-available">
      <question>
        What Jackrabbit file systems are available?
      </question>
      <answer>
        <p>
          The table below lists the currently available Jackrabbit file systems,
          along with the status and pros and cons of each FS.
        </p>
        <table>
          <thead>
            <tr>
              <th>File system</th>
              <th>Status</th>
              <th>Pros</th>
              <th>Cons</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td>LocalFileSystem</td>
              <td>mature</td>
              <td></td>
              <td>
                <ul>
                  <li>Slow on Windows boxes</li>
                </ul>
              </td>
            </tr>
            <tr>
              <td>DbFileSystem</td>
              <td>mature</td>
              <td>
                <ul>
                  <li>JDBC based file system supporting a wide range of RDBMSs</li>
                  <li>zero-deployment, schema is automatically created</li>
                </ul>
              </td>
              <td>
                <ul>
                  <li>Slower than native file systems</li>
                </ul>
              </td>
            </tr>
            <tr>
              <td>CQFS file system</td>
              <td>mature</td>
              <td>
                <ul>
                  <li>Fast on Windows boxes</li>
                </ul>
              </td>
              <td>
                <ul>
                  <li>Undocumented configuration options</li>
                  <li>Proprietary binary format</li>
                  <li>Not open source</li>
                </ul>
              </td>
            </tr>
          </tbody>
        </table>
      </answer>
    </faq>

    <faq id="which-pm-fs">
      <question>
        Which persistence manager and file systems should I use?
      </question>
      <answer>
        <p>
          The answer depends on your priorities. If you want to store your 
          data in a RDBMS, use SimpleDbPersistenceManager and either 
          LocalFileSystem or DbFileSystem. If you want to store your data 
          in an accessible format (just in case or for manual debugging), 
          you might want to try the XMLPersistenceManager and the 
          LocalFileSystem. If you use Windows and performance is a must, 
          you might want to try the ObjectPersistenceManager and the 
          proprietary CQFS.
        </p>
      </answer>
    </faq>
  </part>

</faqs>