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From "Stefan Reich" <...@drjava.de>
Subject Re: [PATCH] Lazy task class loading
Date Tue, 07 Aug 2001 14:33:50 GMT
Hi Ant developers-in-charge,

I sent this to the list two weeks ago and didn't get any reply.

Can you please give me an indication whether this patch is at all useful? Or if you think
it isn't, then tell me why. I would really like to know that.

I have a couple of ideas for other patches to submit; but I don't want to go through the hassle
to prepare them if there is no interest. So I'm using this patch as a kind of test balloon
;-)

Best,
-Stefan
  ----- Original Message ----- 
  From: Stefan Reich 
  To: ant-dev@jakarta.apache.org 
  Sent: Saturday, July 21, 2001 7:25 PM
  Subject: [PATCH] Lazy task class loading


  Hi,

  currently Ant loads all taskdef classes (as defined in defaults.properties) on startup.
This mechanism has at least 3 drawbacks:
   
  -It can take up to one second or longer (if you use ant for everyday development, you will
notice the difference)
  -It wastes memory
  -It completely lacks descriptive error messages. For example, if you use <junit>,
but junit.jar isn't in your classpath, you only get a default message telling you something
about optional.jar. I've been puzzled as to why tasks couldn't be loaded more than once.

  I would like to submit a patch that solves all three problems. I also took care to ensure
that the public interface of org.apache.tools.ant.Project is backward compatible.

  -Stefan

  Here is the patch against recent CVS (I already added @author tags for your convenience
;-):

  Index: main/org/apache/tools/ant/Project.java
  ===================================================================
  RCS file: /home/cvspublic/jakarta-ant/src/main/org/apache/tools/ant/Project.java,v
  retrieving revision 1.64
  diff -u -r1.64 Project.java
  --- main/org/apache/tools/ant/Project.java 2001/07/17 12:12:39 1.64
  +++ main/org/apache/tools/ant/Project.java 2001/07/21 17:03:14
  @@ -68,6 +68,7 @@
    * file paths at runtime as well as defining various project properties.
    *
    * @author duncan@x180.com
  + * @author Stefan Reich <a href="mailto:doc@drjava.de">doc@drjava.de</a>
    */
   
   public class Project {
  @@ -101,7 +102,8 @@
       private Hashtable references = new Hashtable();
       private String defaultTarget;
       private Hashtable dataClassDefinitions = new Hashtable();
  -    private Hashtable taskClassDefinitions = new Hashtable();
  +    private TaskDefinitionHashtable taskClassDefinitions = new TaskDefinitionHashtable();
  +    
       private Hashtable targets = new Hashtable();
       private Hashtable filters = new Hashtable();
       private File baseDir;
  @@ -114,6 +116,27 @@
       /** The system classloader - may be null */    
       private ClassLoader systemLoader = null;
       
  +    public static class TaskDefinitionHashtable extends Hashtable {
  +      /** lazily call Class.forName */
  +      public Object get(Object key) {
  +        Object value = super.get(key);
  +        if (value instanceof String) {
  +          try {
  +            value = Class.forName((String) value);
  +          } catch (ClassNotFoundException e) {
  +            throw new RuntimeException(e.toString());
  +          } catch (NoClassDefFoundError e) {
  +            throw new RuntimeException(e.toString());
  +          }
  +        }
  +        return value;
  +      }
  +      
  +      public String getClassName(Object key) {
  +        return (String) super.get(key);
  +      }
  +    }
  +    
       static {
   
           // Determine the Java version by looking at available classes
  @@ -161,19 +184,23 @@
               props.load(in);
               in.close();
   
  +            long startTime = System.currentTimeMillis();
               Enumeration enum = props.propertyNames();
               while (enum.hasMoreElements()) {
                   String key = (String) enum.nextElement();
                   String value = props.getProperty(key);
  -                try {
  +                /*try {
                       Class taskClass = Class.forName(value);
                       addTaskDefinition(key, taskClass);
                   } catch (NoClassDefFoundError ncdfe) {
                       // ignore...
                   } catch (ClassNotFoundException cnfe) {
                       // ignore...
  -                }
  +                }*/
  +                addTaskDefinition(key, value);
               }
  +            long endTime = System.currentTimeMillis();
  +            System.out.println("Class loading took "+(endTime-startTime)+" ms");
           } catch (IOException ioe) {
               throw new BuildException("Can't load default task list");
           }
  @@ -367,13 +394,19 @@
           log("Detected OS: " + System.getProperty("os.name"), MSG_VERBOSE);
       }
   
  +    public void addTaskDefinition(String taskName, String taskClass) {
  +        String msg = " +User task: " + taskName + "     " + taskClass;
  +        log(msg, MSG_DEBUG);
  +        taskClassDefinitions.put(taskName, taskClass);
  +    }
  +
       public void addTaskDefinition(String taskName, Class taskClass) {
           String msg = " +User task: " + taskName + "     " + taskClass.getName();
           log(msg, MSG_DEBUG);
           taskClassDefinitions.put(taskName, taskClass);
       }
   
  -    public Hashtable getTaskDefinitions() {
  +    public TaskDefinitionHashtable getTaskDefinitions() {
           return taskClassDefinitions;
       }
   
  @@ -445,7 +478,12 @@
       }
   
       public Task createTask(String taskType) throws BuildException {
  -        Class c = (Class) taskClassDefinitions.get(taskType);
  +        Class c;
  +        try {
  +          c = (Class) taskClassDefinitions.get(taskType);
  +        } catch (RuntimeException e) {
  +          throw new BuildException(e.getMessage());
  +        }
   
           if (c == null)
               return null;
  Index: main/org/apache/tools/ant/taskdefs/Ant.java
  ===================================================================
  RCS file: /home/cvspublic/jakarta-ant/src/main/org/apache/tools/ant/taskdefs/Ant.java,v
  retrieving revision 1.23
  diff -u -r1.23 Ant.java
  --- main/org/apache/tools/ant/taskdefs/Ant.java 2001/07/06 11:57:29 1.23
  +++ main/org/apache/tools/ant/taskdefs/Ant.java 2001/07/21 17:03:15
  @@ -76,6 +76,7 @@
    *
    *
    * @author costin@dnt.ro
  + * @author Stefan Reich <a href="mailto:doc@drjava.de">doc@drjava.de</a>
    */
   public class Ant extends Task {
   
  @@ -143,11 +144,11 @@
               }
           }
   
  -        Hashtable taskdefs = project.getTaskDefinitions();
  +        Project.TaskDefinitionHashtable taskdefs = project.getTaskDefinitions();
           Enumeration et = taskdefs.keys();
           while (et.hasMoreElements()) {
               String taskName = (String) et.nextElement();
  -            Class taskClass = (Class) taskdefs.get(taskName);
  +            String taskClass = taskdefs.getClassName(taskName);
               p1.addTaskDefinition(taskName, taskClass);
           }



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