title: What's JSON prefix used for?
body: <p>I know it is a stupid question but I did not find expected answer by Google. One of new feature of Spring MVC 4.3 is supporting to configure JSON prefix</p>
  
  <pre><code>&lt;mvc:message-converters&gt;
      &lt;bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"&gt;
          &lt;property name="jsonPrefix" value=")]}',\n" /&gt;
      &lt;/bean&gt;
  &lt;/mvc:message-converters&gt;
  </code></pre>
  
  <p>So the JSON input/output can look like:</p>
  
  <pre><code>)]}',\n"{\"userName\":\"ABC\",\"emailId\":\"ABC@gmail.com\"}"
  </code></pre>
  
  <p>I know it is for the security purpose. But what is it about concretely?</p>