JSON Jackson custom deserializer to return empty String instead of null

Needed a way to deserialize null values in a JSON as emptry strings (""). This is the shortest I could come with.

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.databind.DeserializationContext; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.deser.std.UntypedObjectDeserializer; import com.fasterxml.jackson.databind.module.SimpleModule;   public class NullHandlerDeserializer extends UntypedObjectDeserializer {     private static final long serialVersionUID = 1L;     @Override   public Object deserialize(JsonParser jp, DeserializationContext ctxt)     throws IOException {     switch (jp.getCurrentToken()) {      case VALUE_NULL:            return "";      default:       return super.deserialize(jp, ctxt);     }     }  }

The class extends from an existing deserializer implementation to avoid having to code the handling of all JSON tokens. I needed to worry only about VALUE_NULL token.

And to configure the custom deserializer in the ObjectMapper:

?

1 2 3 4

ObjectMapper om = new ObjectMapper(); SimpleModule module = new SimpleModule(); module.addDeserializer(Object.class, new NullHandlerDeserializer()); om.registerModule(module);

XSLT Learnings

Just listing some XSLT learnings from a recent project where I had to learn from scratch.

Basic shelling:

?

1 2 3 4 5 6 7

<?xml version="1.0" encoding="ISO-8859-1"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0"> <xsl:output method="xml" encoding="utf-8" indent="no"/> <xsl:template match="/">     <!-- XSL stuff --> </xsl:template> </xsl:stylesheet>

Converting a list of states from XML to HTML select input options:

Given an input like this:

?

1 2 3 4 5 6 7

<states>     <AL>Alabama</AL>     <AK>Alaska</AK>     <AR>Arkansas</AR>     <CA>California</CA>     <CO>Colorado</CO> </states>

Use XSL like this:

?

1 2 3 4 5 6 7 8

<select name="states">     <xsl:for-each select="states/*">         <option>              <xsl:attribute name="value"><xsl:value-of select="name(.)"/></xsl:attribute>         </option>         <xsl:value-of select="string(.)"/>     </xsl:for-each> </select>

To get this:

?

1 2 3 4 5 6 7

<select>         <option value="AL">Alabama</option>         <option value="AK">Alaska</option>         <option value="AR">Arkansas</option>         <option value="CA">California</option>         <option value="CO">Colorado</option> </select>

Some few things to note:

• "name(.)" gives you the element (tag) name.
• "string(.)" gives you the element value (what is between opening and closong tags).

Checking element has children or content

?

1 2 3

<xsl:if test="some/element-tag/text() != ''"> ... </xsl:if>