Allow registration of custom relations

diff --git a/src/main/java/org/z3950/zing/cql/CQLParser.java b/src/main/java/org/z3950/zing/cql/CQLParser.java
index 2509563..6bd6d01 100644 (file)
--- a/src/main/java/org/z3950/zing/cql/CQLParser.java
+++ b/src/main/java/org/z3950/zing/cql/CQLParser.java
@@ -8,7 +8,9 @@ import java.io.FileNotFoundException;
 import java.io.Reader;
 import java.io.StringReader;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
 
 /**
@@ -21,6 +23,8 @@ public class CQLParser {
     private CQLLexer lexer;
     private PositionAwareReader par; //active reader with position
     private int compat;        // When false, implement CQL 1.2
+    private final Set<String> customRelations = new HashSet<String>();
+    
     public static final int V1POINT1 = 12368;
     public static final int V1POINT2 = 12369;
     public static final int V1POINT1SORT = 12370;
@@ -58,6 +62,25 @@ public class CQLParser {
     }
     
     /**
+     * Registers custom relation in this parser. Note that when a custom relation
+     * is registered the parser is no longer strictly compliant with the chosen spec.
+     * @param relation
+     * @return true if custom relation has not been registered already
+     */
+    public boolean registerCustomRelation(String relation) {
+      return customRelations.add(relation);
+    }
+    
+    /**
+     * Unregisters previously registered custom relation in this instance of the parser.
+     * @param relation
+     * @return true is relation has been previously registered
+     */
+    public boolean unregisterCustomRelation(String relation) {
+      return customRelations.remove(relation);
+    }
+    
+    /**
      * Compiles a CQL query.
      * <P>
      * The resulting parse tree may be further processed by hand (see
@@ -272,7 +295,8 @@ public class CQLParser {
              lexer.sval.equals("encloses") ||
              (lexer.sval.equals("exact") && compat != V1POINT2) ||
              (lexer.sval.equals("scr") && compat != V1POINT2) ||
-             (lexer.sval.equals("adj") && compat == V1POINT2)))
+             (lexer.sval.equals("adj") && compat == V1POINT2) ||
+             customRelations.contains(lexer.sval)))
           return true;
 
         return isSymbolicRelation();
@@ -444,6 +468,7 @@ public class CQLParser {
        }
 
        CQLParser parser = new CQLParser(compat);
+        parser.registerCustomRelation("@");
        CQLNode root = null;
        try {
            root = parser.parse(cql);