allow col validator to get this column by name

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/branches/exprs@1161 f203690c-595d-4dc9-a70b-905162fa7fd2

src/main/java/com/healthmarketscience/jackcess/impl/ColValidatorEvalContext.java

 
 import com.healthmarketscience.jackcess.Column;
 import com.healthmarketscience.jackcess.InvalidValueException;
+import com.healthmarketscience.jackcess.expr.EvalException;
+import com.healthmarketscience.jackcess.expr.Identifier;
 import com.healthmarketscience.jackcess.expr.Value;
 import com.healthmarketscience.jackcess.impl.expr.Expressionator;
 import com.healthmarketscience.jackcess.util.ColumnValidator;
     return toValue(_val, getCol().getType());
   }
 
+  @Override
+  public Value getIdentifierValue(Identifier identifier) {
+    // col validators can only get "this" column, but they can refer to it by
+    // name
+    if(!getCol().isThisColumn(identifier)) {
+      throw new EvalException("Cannot access other fields for " + identifier);
+    }
+    return getThisColumnValue();
+  }
+
   private Object validate(Column col, Object val) throws IOException {
     try {
       _val = val;

src/main/java/com/healthmarketscience/jackcess/impl/ColumnImpl.java

 import com.healthmarketscience.jackcess.complex.ComplexColumnInfo;
 import com.healthmarketscience.jackcess.complex.ComplexValue;
 import com.healthmarketscience.jackcess.complex.ComplexValueForeignKey;
+import com.healthmarketscience.jackcess.expr.Identifier;
 import com.healthmarketscience.jackcess.impl.complex.ComplexValueForeignKeyImpl;
 import com.healthmarketscience.jackcess.util.ColumnValidator;
 import com.healthmarketscience.jackcess.util.SimpleColumnValidator;
     return withErrorContext(msg, getDatabase(), getTable().getName(), getName());
   }
 
+  boolean isThisColumn(Identifier identifier) {
+    return(getTable().isThisTable(identifier) &&
+           identifier.getObjectName().equalsIgnoreCase(getName()));
+  }
+
   private static String withErrorContext(
       String msg, DatabaseImpl db, String tableName, String colName) {
     return msg + " (Db=" + db.getName() + ";Table=" + tableName + ";Column=" +