correct html, add helpers

help/en/html/doc/Technical/XmlPersistance.shtml

@@ -143,6 +143,11 @@
 
       <p>Boolean values should be stored as the strings "true" and "false".</p>
 
+      <p>The <code>getAttributeIntegerValue</code> and 
+      <code>getAttributeBooleanValue</code>
+      methods provide a simple way of parsing input and handling errors.
+      </p>
+
       <p>Although much of the early code stored information in attributes, 
       consider putting the data being stored in elements instead.  This 
       makes for simpler XML Schema and XSLT definitions, and the structured nature can 
@@ -159,10 +164,20 @@
       "http://jmri.org/JavaDoc/doc/jmri/configurexml/AbstractTurnoutManagerConfigXML.html">
       jmri.configurexml.AbstractSensorManagerConfigXML</a>, which
       does almost all the work of storing and loading sensors.</p>
-
-      <h3><a id="enum" name="refs">Persisting enum values</h3>
 
-    The “EnumIO” tool built into AbstractXmlAdapter that reads and writes enums via the names of their elements.
+
+      <h3><a id="errors" name="errors">Handling Errors</a></h3>
+
+      If theres a parsing error, exception, etc, it should be reported
+      via the ErrorHandler.  This accumulates reports and presents them
+      (in a almost-useful way) to the user when appropriate.
+      <p>
+      For an example of how to do that, see the <code>getAttributeBooleanValue</code>
+      method.
+
+      <h3><a id="enum" name="enum">Persisting enum values</a></h3>
+
+    The "EnumIO" tool built into AbstractXmlAdapter that reads and writes enums via the names of their elements.
     <p>
     You add a member in your configureXml load/store class:
 <pre>
@@ -172,13 +187,13 @@
     variable, you pass the enum value through that map element in your <code>store</code> method:
 
 <pre>
-            element.setAttribute(“name", "" + enumMap.outputFromEnum(myEnumValue));
+            element.setAttribute("name", "" + enumMap.outputFromEnum(myEnumValue));
 </pre><br>
 Storing into an element is similar
 
 To restore the value on load:
 <pre>
-	myEnumValue = enumMap.inputFromAttribute(element.getAttribute(“name"));
+	myEnumValue = enumMap.inputFromAttribute(element.getAttribute("name"));
 </pre><br>
 
       There are several variations available, please see 
@@ -197,6 +212,8 @@ To restore the value on load:
                     the values loaded and stored.  It's possible to provide multiple
                     load values that make to a single enum value, i.e. "3" and "Ralph".
       </ul>
+
+
       <h3><a id="refs" name="refs">Persisting References to NamedBeans</a></h3>
 
       Classes should, but don't always, 

java/src/jmri/configurexml/AbstractXmlAdapter.java

@@ -91,7 +91,65 @@ public ErrorHandler getExceptionHandler() {
         return this.errorHandler;
     }
 
+    /**
+     * Service method to handle attribute input of
+     * boolean  (true/yes vs false/no) values.  Not being present
+     * is not an error. Not parsing (which shouldn't happen due to
+     * the XML Schema checks) invokes the default error handler.
+     */
+    final public boolean getAttributeBooleanValue(@Nonnull Element element, @Nonnull String name, boolean def) {
+        Attribute a = null;
+        String val = null;
+        try {
+            a = element.getAttribute(name);
+            if (a == null) return def;
+            val = a.getValue();
+            if ( val.equals("yes") || val.equals("true") ) return true;  // non-externalized strings
+            if ( val.equals("no") || val.equals("false") ) return false;
+            return def;
+        } catch (Exception ex) {
+            log.debug("caught exception", ex);
+            ErrorMemo em = new ErrorMemo(this,
+                                            "getAttributeBooleanValue threw exception",
+                                            "element: "+element.getName(),
+                                            "attribute: "+name,
+                                            "value: "+val,
+                                            ex);
+            getExceptionHandler().handle(em);
+            return def;
+        }
+    }
 
+    /**
+     * Service method to handle attribute input of
+     * integer values.  Not being present
+     * is not an error. Not parsing (which shouldn't happen due to
+     * the XML Schema checks) invokes the default error handler.
+     */
+    final public int getAttributeIntegerValue(@Nonnull Element element, @Nonnull String name, int def) {
+        Attribute a = null;
+        String val = null;
+        try {
+            a = element.getAttribute(name);
+            if (a == null) return def;
+            val = a.getValue();
+            return a.getIntValue();
+        } catch (Exception ex) {
+            log.debug("caught exception", ex);
+            ErrorMemo em = new ErrorMemo(this,
+                                            "getAttributeIntegerValue threw exception",
+                                            "element: "+element.getName(),
+                                            "attribute: "+name,
+                                            "value: "+val,
+                                            ex);
+            getExceptionHandler().handle(em);
+            return def;
+        }
+    }
+
+    /**
+     * Base for support of Enum load/store to XML files
+     */
     public static abstract class EnumIO <T extends Enum<T>> { // public to be usable by adapters in other configXML packages
 
         /**

java/test/jmri/configurexml/AbstractXmlAdapterTest.java

@@ -1,6 +1,7 @@
 package jmri.configurexml;
 
 import java.util.HashMap;
+import org.jdom2.*;
 import org.junit.*;
 
 /**
@@ -10,6 +11,54 @@
  */
 public class AbstractXmlAdapterTest{
 
+    @Test
+    public void testGetAttributeBooleanValue() {
+        AbstractXmlAdapter adapter  = new AbstractXmlAdapter(){
+            public Element store(Object o) {return null;}
+            public void load(Element e, Object o) {}
+        };
+
+        Element testEl = new Element("foo");
+
+        Assert.assertTrue(adapter.getAttributeBooleanValue(testEl, "att", true));
+        Assert.assertFalse(adapter.getAttributeBooleanValue(testEl, "att", false));
+
+        testEl.setAttribute("t", "true");
+        testEl.setAttribute("f", "false");
+        testEl.setAttribute("y", "yes");
+        testEl.setAttribute("n", "no");
+
+        Assert.assertTrue(adapter.getAttributeBooleanValue(testEl, "t", true));
+        Assert.assertTrue(adapter.getAttributeBooleanValue(testEl, "t", false));
+
+        Assert.assertFalse(adapter.getAttributeBooleanValue(testEl, "f", true));
+        Assert.assertFalse(adapter.getAttributeBooleanValue(testEl, "f", false));
+
+        Assert.assertTrue(adapter.getAttributeBooleanValue(testEl, "y", true));
+        Assert.assertTrue(adapter.getAttributeBooleanValue(testEl, "y", false));
+
+        Assert.assertFalse(adapter.getAttributeBooleanValue(testEl, "n", true));
+        Assert.assertFalse(adapter.getAttributeBooleanValue(testEl, "n", false));
+
+
+    }
+
+    @Test
+    public void testGetAttributeIintegerValue() {
+        AbstractXmlAdapter adapter  = new AbstractXmlAdapter(){
+            public Element store(Object o) {return null;}
+            public void load(Element e, Object o) {}
+        };
+
+        Element testEl = new Element("foo");
+
+        Assert.assertEquals(12, adapter.getAttributeIntegerValue(testEl, "att", 12));
+
+        testEl.setAttribute("t21", "21");
+
+        Assert.assertEquals(21, adapter.getAttributeIntegerValue(testEl, "t21", 12));
+    }
+
     enum testEnum {Foo, Bar, Biff}
 
     @Test