commit f92debf3c7648a6e11edc1e4d6c1ec3d3221a4bb
author Shawn O. Pearce <sop@google.com> Wed Jun 01 09:14:27 2011 -0700
committer Shawn O. Pearce <sop@google.com> Thu Jun 02 07:48:01 2011 -0700
tree b3178791702e73160feeba53c388b1a966215d0c
parent 3127a9e43e864f2556c0dcdc529172d3e04fb357

Allow PrologControl to set the PrologClassLoader

This permits embedding applications to choose which ClassLoader will
provide the Prolog predicates available to the runtime. If none is
configured, the engine will use the system ClassLoader.

src/lang/Prolog.java

diff --git a/src/lang/Prolog.java b/src/lang/Prolog.java
index f9b3d5e..693bcfe 100644
--- a/src/lang/Prolog.java
+++ b/src/lang/Prolog.java
@@ -115,8 +115,6 @@
 	cont       = null;
 	stack      = new CPFStack(this);
 	trail      = new Trail(this);
-	//	pdl        = new PushDownList();
-	pcl        = new PrologClassLoader();
     }
 
     /** 
@@ -134,6 +132,8 @@
      */
     protected void initOnce() {
 	aregs      = new Term[maxArity];
+	if (pcl == null)
+	  pcl = new PrologClassLoader();
 	if (internalDB == null)
 	  internalDB = new InternalDatabase();
 

src/lang/PrologClassLoader.java

diff --git a/src/lang/PrologClassLoader.java b/src/lang/PrologClassLoader.java
index 2d5e0a7..5bd4bc5 100644
--- a/src/lang/PrologClassLoader.java
+++ b/src/lang/PrologClassLoader.java
@@ -8,6 +8,18 @@
  * @version 1.1
  */
 public class PrologClassLoader extends ClassLoader implements Serializable {
+    /** Initialize using the {@link ClassLoader#getSystemClassLoader()}.  */
+    public PrologClassLoader() {
+    }
+
+    /**
+     * Initialize using a specific parent ClassLoader.
+     *
+     * @param parent source for all predicates in this context.
+     */
+    public PrologClassLoader(ClassLoader parent) {
+      super(parent);
+    }
 
     /**
      * Returns a <code>java.lang.Class</code> object associated with the predicate

src/lang/PrologControl.java

diff --git a/src/lang/PrologControl.java b/src/lang/PrologControl.java
index 875c096..9d5cc31 100644
--- a/src/lang/PrologControl.java
+++ b/src/lang/PrologControl.java
@@ -43,6 +43,17 @@
       engine.internalDB = new InternalDatabase(size);
     }
 
+    public PrologClassLoader getPrologClassLoader() {
+      if (engine.pcl == null)
+        engine.pcl = new PrologClassLoader();
+      return engine.pcl;
+    }
+    public void setPrologClassLoader(PrologClassLoader cl) {
+      if (engine.aregs != null)
+        throw new IllegalStateException("Prolog already initialized");
+      engine.pcl = cl;
+    }
+
     public int getMaxArity() { return engine.getMaxArity(); }
     public void setMaxArity(int max) {
       if (max < 8)
@@ -67,7 +78,7 @@
      */
     public void setPredicate(Term t)  {
 	try {
-	    Class clazz = engine.pcl.loadPredicateClass("jp.ac.kobe_u.cs.prolog.builtin", "call", 1, true);
+	    Class clazz = getPrologClassLoader().loadPredicateClass("jp.ac.kobe_u.cs.prolog.builtin", "call", 1, true);
 	    Term[] args = {engine.copy(t)};
 	    code = (Predicate)(clazz.newInstance());
 	    code.setArgument(args, new Success(this));