title: Jackson JSON ObjectMapper.readvalue
body: <p>I'm going through code examples on converting the Java object to a JSON and I came across this:</p>
  
  <pre><code>HashMap&lt;String, Object&gt; filters = new ObjectMapper().readValue(filterStr, HashMap.class);
  </code></pre>
  
  <p>where </p>
  
  <pre><code>String filterStr;
  </code></pre>
  
  <p>sorry, but what exactly is the above line of code doing? I went through other example <a href="http://www.mkyong.com/java/how-to-convert-java-object-to-from-json-jackson/" rel="nofollow">here.</a> I can see that readValue() has been overridden but how can a string be converted to a HashMap? Shouldn't it be a JSON object and not a string? Thanks.</p>