Custom JSP taglib to convert Object to JSON

The times for direct javascript DOM manipulation are gone. Modern frameworks like Angular.js demand JSON to be available. Finally if you use a hybrid approach where there is a need for server side HTML templates, the need to expose objects in JSON format will be unavoidable.

Using simple JSP views thorugh the help of taglibs should be a clean way to give front end developers what they need. They should be able to get a JSON for their javascript needs in a single line:

<script>
  var employees = ${ju:toJson(employees)};
</script>

Here is all you need to do in the back-end(middle tier). First you need a utility class that can take an object and serialize it to JSON. The winner in my journey so far is Jackson API so:

package com.nestorurquiza.utils;

import java.io.IOException;

import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;

import com.nestorurquiza.serialization.JacksonObjectMapper;

public final class JsonUtils {

 private JsonUtils() {
 }

 public static String toJson(Object value) throws JsonGenerationException, JsonMappingException, IOException {
  JacksonObjectMapper mapper = new JacksonObjectMapper();
  return mapper.writeValueAsString(value);
 }

}

Here is the custom JsonObjectMapper class:

package com.nestorurquiza.serialization;

import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class JacksonObjectMapper extends ObjectMapper {

 private static final Logger log = LoggerFactory.getLogger(JacksonObjectMapper.class);

 public JacksonObjectMapper() {
  configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS, false);
 }
}

Here is the taglib descriptor file /WEB-INF/tld/Json.tld:

<?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemalocation="http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    <tlib-version>2.1</tlib-version>
    <uri>JsonUtils</uri>
     
    <function>
        <name>toJson</name>
        <function-class>com.nestorurquiza.utils.JsonUtils</function-class>
        <function-signature>
            String toJson(java.lang.Object)
        </function-signature>
    </function>
</taglib>

Finally do not forget to include the taglib to use from JSP:

<%@ taglib prefix="ju" uri="/WEB-INF/tld/JsonUtils.tld"%>