Class ModifiedSelector

  • All Implemented Interfaces:
    java.lang.Cloneable, java.util.EventListener, BuildListener, Parameterizable, ResourceSelector, ExtendFileSelector, FileSelector

    public class ModifiedSelector
    extends BaseExtendSelector
    implements BuildListener, ResourceSelector

    Selector class that uses Algorithm, Cache and Comparator for its work. The Algorithm is used for computing a hashvalue for a file. The Comparator decides whether to select or not. The Cache stores the other value for comparison by the Comparator in a persistent manner.

    The ModifiedSelector is implemented as a CoreSelector and uses default values for all its attributes therefore the simplest example is

       <copy todir="dest">
           <filelist dir="src">
               <modified/>
           </filelist>
       </copy>
     

    The same example rewritten as CoreSelector with setting the all values (same as defaults are) would be

       <copy todir="dest">
           <filelist dir="src">
               <modified update="true"
                         cache="propertyfile"
                         algorithm="digest"
                         comparator="equal">
                   <param name="cache.cachefile"     value="cache.properties"/>
                   <param name="algorithm.algorithm" value="MD5"/>
               </modified>
           </filelist>
       </copy>
     

    And the same rewritten as CustomSelector would be

       <copy todir="dest">
           <filelist dir="src">
               <custom class="org.apache.tools.ant.type.selectors.ModifiedSelector">
                   <param name="update"     value="true"/>
                   <param name="cache"      value="propertyfile"/>
                   <param name="algorithm"  value="digest"/>
                   <param name="comparator" value="equal"/>
                   <param name="cache.cachefile"     value="cache.properties"/>
                   <param name="algorithm.algorithm" value="MD5"/>
               </custom>
           </filelist>
       </copy>
     

    If you want to provide your own interface implementation you can do that via the *classname attributes. If the classes are not on Ant's core classpath, you will have to provide the path via nested <classpath> element, so that the selector can find the classes.

       <modified cacheclassname="com.mycompany.MyCache">
           <classpath>
               <pathelement location="lib/mycompany-antutil.jar"/>
           </classpath>
       </modified>
     

    All these three examples copy the files from src to dest using the ModifiedSelector. The ModifiedSelector uses the PropertyfileCache , the DigestAlgorithm and the EqualComparator for its work. The PropertyfileCache stores key-value-pairs in a simple java properties file. The filename is cache.properties. The update flag lets the selector update the values in the cache (and on first call creates the cache). The DigestAlgorithm computes a hashvalue using the java.security.MessageDigest class with its MD5-Algorithm and its standard provider. The new computed hashvalue and the stored one are compared by the EqualComparator which returns 'true' (more correct a value not equals zero (1)) if the values are not the same using simple String comparison.

    A useful scenario for this selector is inside a build environment for homepage generation (e.g. with Apache Forrest).

     <target name="generate-and-upload-site">
         <echo> generate the site using forrest </echo>
         <antcall target="site"/>
    
         <echo> upload the changed files </echo>
         <ftp server="${ftp.server}" userid="${ftp.user}" password="${ftp.pwd}">
             <fileset dir="htdocs/manual">
                 <modified/>
             </fileset>
         </ftp>
     </target>
     

    Here all changed files are uploaded to the server. The ModifiedSelector saves therefore much upload time.

    This selector uses reflection for setting the values of its three interfaces (using org.apache.tools.ant.IntrospectionHelper) therefore no special 'configuration interfaces' has to be implemented by new caches, algorithms or comparators. All present setXX methods can be used. E.g. the DigestAlgorithm can use a specified provider for computing its value. For selecting this there is a setProvider(String providername) method. So you can use a nested <param name="algorithm.provider" value="MyProvider"/>.

    Since:
    Ant 1.6
    • Constructor Detail

      • ModifiedSelector

        public ModifiedSelector()
        Bean-Constructor.
    • Method Detail

      • verifySettings

        public void verifySettings()
        Overrides BaseSelector.verifySettings().
        Overrides:
        verifySettings in class BaseSelector
      • configure

        public void configure()
        Configures this Selector. Does this work only once per Selector object.

        Because some problems while configuring from <custom>Selector the configuration is done in the following order:

        1. collect the configuration data
        2. wait for the first isSelected() call
        3. set the default values
        4. set values for name pattern '*': update, cache, algorithm, comparator
        5. set values for name pattern '*.*: cache.cachefile, ...

        This configuration algorithm is needed because you don't know the order of arriving config-data. E.g. if you first set the cache.cachefilename and after that the cache itself, the default value for cachefilename is used, because setting the cache implies creating a new Cache instance - with its defaults.

      • loadClass

        protected <T> T loadClass​(java.lang.String classname,
                                  java.lang.String msg,
                                  java.lang.Class<? extends T> type)
        Loads the specified class and initializes an object of that class. Throws a BuildException using the given message if an error occurs during loading/instantiation or if the object is not from the given type.
        Type Parameters:
        T - desired type
        Parameters:
        classname - the classname
        msg - the message-part for the BuildException
        type - the type to check against
        Returns:
        a castable object
      • isSelected

        public boolean isSelected​(java.io.File basedir,
                                  java.lang.String filename,
                                  java.io.File file)
        Implementation of BaseExtendSelector.isSelected().
        Specified by:
        isSelected in interface FileSelector
        Specified by:
        isSelected in class BaseExtendSelector
        Parameters:
        basedir - as described in BaseExtendSelector
        filename - as described in BaseExtendSelector
        file - as described in BaseExtendSelector
        Returns:
        as described in BaseExtendSelector
      • saveCache

        protected void saveCache()
        save the cache file
      • setAlgorithmClass

        public void setAlgorithmClass​(java.lang.String classname)
        Setter for algorithmClass.
        Parameters:
        classname - new value
      • setComparatorClass

        public void setComparatorClass​(java.lang.String classname)
        Setter for comparatorClass.
        Parameters:
        classname - new value
      • setCacheClass

        public void setCacheClass​(java.lang.String classname)
        Setter for cacheClass.
        Parameters:
        classname - new value
      • setUpdate

        public void setUpdate​(boolean update)
        Support for update attribute.
        Parameters:
        update - new value
      • setSeldirs

        public void setSeldirs​(boolean seldirs)
        Support for seldirs attribute.
        Parameters:
        seldirs - new value
      • setSelres

        public void setSelres​(boolean newValue)
        Support for selres attribute.
        Parameters:
        newValue - the new value
      • getModified

        public int getModified()
        Getter for the modified count
        Returns:
        modified count
      • setModified

        public void setModified​(int modified)
        Setter for the modified count
        Parameters:
        modified - count
      • getDelayUpdate

        public boolean getDelayUpdate()
        Getter for the delay update
        Returns:
        true if we should delay for performance
      • setDelayUpdate

        public void setDelayUpdate​(boolean delayUpdate)
        Setter for the delay update
        Parameters:
        delayUpdate - true if we should delay for performance
      • addClasspath

        public void addClasspath​(Path path)
        Add the classpath.
        Parameters:
        path - the classpath
      • getClassLoader

        public java.lang.ClassLoader getClassLoader()
        Returns and initializes the classloader for this class.
        Returns:
        the classloader
      • setClassLoader

        public void setClassLoader​(java.lang.ClassLoader loader)
        Set the used ClassLoader. If you invoke this selector by API (e.g. inside some testcases) the selector will use a different classloader for loading the interface implementations than the caller. Therefore you will get a ClassCastException if you get the implementations from the selector and cast them.
        Parameters:
        loader - the ClassLoader to use
      • addParam

        public void addParam​(java.lang.String key,
                             java.lang.Object value)
        Support for nested <param> tags.
        Parameters:
        key - the key of the parameter
        value - the value of the parameter
      • addParam

        public void addParam​(Parameter parameter)
        Support for nested <param> tags.
        Parameters:
        parameter - the parameter object
      • useParameter

        public void useParameter​(Parameter parameter)
        Support for nested <param name="" value=""/> tags. Parameter named cache, algorithm, comparator or update are mapped to the respective set-Method. Parameter which names starts with cache. or algorithm. or comparator. are tried to set on the appropriate object via its set-methods. Other parameters are invalid and an BuildException will be thrown.
        Parameters:
        parameter - Key and value as parameter object
      • tryToSetAParameter

        protected void tryToSetAParameter​(java.lang.Object obj,
                                          java.lang.String name,
                                          java.lang.String value)
        Try to set a value on an object using reflection. Helper method for easier access to IntrospectionHelper.setAttribute().
        Parameters:
        obj - the object on which the attribute should be set
        name - the attributename
        value - the new value
      • toString

        public java.lang.String toString()
        Override Object.toString().
        Overrides:
        toString in class DataType
        Returns:
        information about this selector
      • buildStarted

        public void buildStarted​(BuildEvent event)
        Signals that a build has started.
        Specified by:
        buildStarted in interface BuildListener
        Parameters:
        event - received BuildEvent
      • getCache

        public Cache getCache()
        Get the cache type to use.
        Returns:
        the enumerated cache type
      • setCache

        public void setCache​(ModifiedSelector.CacheName name)
        Set the cache type to use.
        Parameters:
        name - an enumerated cache type.
      • getAlgorithm

        public Algorithm getAlgorithm()
        Get the algorithm type to use.
        Returns:
        the enumerated algorithm type
      • setAlgorithm

        public void setAlgorithm​(ModifiedSelector.AlgorithmName name)
        Set the algorithm type to use.
        Parameters:
        name - an enumerated algorithm type.
      • getComparator

        public java.util.Comparator<? super java.lang.String> getComparator()
        Get the comparator type to use.
        Returns:
        the enumerated comparator type
      • setComparator

        public void setComparator​(ModifiedSelector.ComparatorName name)
        Set the comparator type to use.
        Parameters:
        name - an enumerated comparator type.