package-summary.html

Geotools是一个开源的Java GIS工具包,可利用它来开发符合标准的地理信息系统。Geotools提供了OGC(Open Geospatial Consortium)规范的一个实现来作为他们的

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<B>Exception Summary</B></FONT></TD>
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<TD WIDTH="15%"><B><A HREF="../../../org/geotools/factory/FactoryNotFoundException.html" title="class in org.geotools.factory">FactoryNotFoundException</A></B></TD>
<TD>Thrown when a factory can't be found in the registery.</TD>
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<TD WIDTH="15%"><B><A HREF="../../../org/geotools/factory/FactoryRegistryException.html" title="class in org.geotools.factory">FactoryRegistryException</A></B></TD>
<TD>Thrown when a factory can't be found or can't be instantiate.</TD>
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<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="../../../org/geotools/factory/RecursiveSearchException.html" title="class in org.geotools.factory">RecursiveSearchException</A></B></TD>
<TD>Thrown when <A HREF="../../../org/geotools/factory/FactoryRegistry.html" title="class in org.geotools.factory"><CODE>FactoryRegistry</CODE></A> is invoked recursively for the same category. </TD>
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<TD COLSPAN=2><FONT SIZE="+2">
<B>Error Summary</B></FONT></TD>
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<TR BGCOLOR="white" CLASS="TableRowColor">
<TD WIDTH="15%"><B><A HREF="../../../org/geotools/factory/FactoryConfigurationError.html" title="class in org.geotools.factory">FactoryConfigurationError</A></B></TD>
<TD><B>Deprecated.</B>&nbsp;<I>This error was used by <A HREF="../../../org/geotools/factory/FactoryFinder.html" title="class in org.geotools.factory"><CODE>FactoryFinder</CODE></A>. </I></TD>
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<P>
<A NAME="package_description"><!-- --></A><H2>
Package org.geotools.factory Description
</H2>

<P>
Utility classes which enable dynamic binding to factory implementations at runtime.

    <P ALIGN="justify">Because Geotools core API consists almost exclusively of interfaces
    (including <A HREF="http://geoapi.sourceforge.net">GeoAPI</A>), factories play a role
    in how developers use the API. Although the interfaces that are declared in GeoAPI are
    implemented in various Geotools packages you should not use those classes directly.
    Instead you should use factories.</P>

    <P ALIGN="justify">J2SE's <A HREF="http://java.sun.com/j2se/1.4/docs/api/javax/imageio/spi/ServiceRegistry.html" title="class or interface in javax.imageio.spi"><CODE>ServiceRegistry</CODE></A> provides a general
    way (even if it is defined in a  subpackage) to instantiate and
    manage factories (also called providers). Each factory implementation should be declared
    in  directory, usually bundled in every JAR file. For example
    if a JAR file provides one or more <CODE>DatumFactory</CODE>
    implementations, then it must provide the following file:</P>

    <BLOCKQUOTE><PRE><B>META-INF/services/</B>org.opengis.referencing.datum.DatumFactory</PRE></BLOCKQUOTE>

    <P ALIGN="justify">with a content similar to the one below:</P>

    <BLOCKQUOTE><PRE>com.mycompany.MyDatumFactory1
com.mycompany.MyDatumFactory2
com.mycompany.MyDatumFactory3</PRE></BLOCKQUOTE>

    <P ALIGN="justify">The ordering is initially unspecified. Users can
    <A HREF="http://java.sun.com/j2se/1.4/docs/api/javax/imageio/spi/ServiceRegistry.html#setOrdering(java.lang.Class, java.lang.Object, java.lang.Object)" title="class or interface in javax.imageio.spi">set an ordering</A>
    explicitly themselves, or implementations can do that automatically
    <A HREF="http://java.sun.com/j2se/1.4/docs/api/javax/imageio/spi/RegisterableService.html#onRegistration(javax.imageio.spi.ServiceRegistry, java.lang.Class)" title="class or interface in javax.imageio.spi">on registration</A>.
    The <A HREF="../../../org/geotools/factory/AbstractFactory.html" title="class in org.geotools.factory"><CODE>AbstractFactory</CODE></A> class provides a simple way to setup ordering
    on registration on the basis of a <A HREF="../../../org/geotools/factory/AbstractFactory.html#priority">priority</A>
    number.</P>

    <P ALIGN="justify">If a user wants a specific implementation, he can
    <A HREF="http://java.sun.com/j2se/1.4/docs/api/javax/imageio/spi/ServiceRegistry.html#getServiceProviders(java.lang.Class, boolean)" title="class or interface in javax.imageio.spi">iterates through registered ones</A>
    and pickup the desired implementation himself. An alternative is to bundle the criterions in a
    <A HREF="../../../org/geotools/factory/Hints.html" title="class in org.geotools.factory">map of hints</A> and lets the registry selects an implementation
    accordingly. This later functionality is not provided by the standard <A HREF="http://java.sun.com/j2se/1.4/docs/api/javax/imageio/spi/ServiceRegistry.html" title="class or interface in javax.imageio.spi"><CODE>ServiceRegistry</CODE></A>,
    but is provided by Geotools's <A HREF="../../../org/geotools/factory/FactoryRegistry.html" title="class in org.geotools.factory"><CODE>FactoryRegistry</CODE></A> extension. This class extends
    the service registry API with the following functionalities:</P>

    <UL>
      <LI><P ALIGN="justify">A <A HREF="../../../org/geotools/factory/FactoryRegistry.html#scanForPlugins()"><CODE>scanForPlugins()</CODE></A> method that scans for plugins in the
          <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/lang/Class.html#getClassLoader()" title="class or interface in java.lang">registry class loader</A>, the
          <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/lang/Thread.html#getContextClassLoader()" title="class or interface in java.lang">thread context class loader</A> and the
          <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/lang/ClassLoader.html#getSystemClassLoader()" title="class or interface in java.lang">system class loader</A>.
          Additionally,  looks for any implementation specified as
          <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/lang/System.html#getProperty(java.lang.String)" title="class or interface in java.lang">system property</A>.</P></LI>

      <LI><P ALIGN="justify">Filters out automatically <A HREF="../../../org/geotools/factory/OptionalFactory.html" title="interface in org.geotools.factory">optional factories</A>
          when they are not <A HREF="../../../org/geotools/factory/OptionalFactory.html#isAvailable()">available</A>.</P></LI>

      <LI><P ALIGN="justify">When more than one implementation is available for the same <A HREF="../../../org/geotools/factory/Factory.html" title="interface in org.geotools.factory"><CODE>Factory</CODE></A>
          subinterface, an optional set of <A HREF="../../../org/geotools/factory/Hints.html" title="class in org.geotools.factory">hints</A> can specifies the criterions that the
          desired implementation must meets. If a factory implementation depends on other factories, the dependencies hints
          are checked recursively.</P></LI>

      <LI><P ALIGN="justify"><U>Optionally</U>, if no factory matches the given hints, a new instance can be
          <A HREF="../../../org/geotools/factory/FactoryCreator.html#createServiceProvider(java.lang.Class, java.lang.Class, org.geotools.factory.Hints)">automatically created</A>.
          However, those new instances are not registered. If creation of new instances at every
          <A HREF="../../../org/geotools/factory/FactoryRegistry.html#getServiceProvider(java.lang.Class, javax.imageio.spi.ServiceRegistry.Filter, org.geotools.factory.Hints, org.geotools.factory.Hints.Key)"><CODE>getServiceProvider(...)</CODE></A>
          method invocation is undesired, an implementation matching the expected
          <A HREF="../../../org/geotools/factory/Hints.html" title="class in org.geotools.factory">hints</A> should be registered in the
           directory, as explained above.</P></LI>
    </UL>

    <P ALIGN="justify">Note that the <A HREF="../../../org/geotools/factory/Hints.html" title="class in org.geotools.factory">hints</A>, if provided, don't need to apply
    directly to the requested factory category. They may apply indirectly through some dependency. A typical example is
    a request for any <A HREF="http://www.jump-project.org/docs/jts/1.7/api/com/vividsolutions/jts/geom/GeometryFactory.html" title="class or interface in com.vividsolutions.jts.geom"><CODE>GeometryFactory</CODE></A> instance, providing that this instance uses a
    particular <A HREF="http://www.jump-project.org/docs/jts/1.7/api/com/vividsolutions/jts/geom/CoordinateSequenceFactory.html" title="class or interface in com.vividsolutions.jts.geom"><CODE>CoordinateSequenceFactory</CODE></A> implementation.</P>
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