Java jakeson json转Map。求帮助，求代码。

 {"new_terminal":{"term":2,"rows":40,"cols":185,"em_dimensions":{"w":7,"h":14.96875}}}

现在想把他转换成一个嵌套着的Map。弄了好久都失败了。
用的是jakeson,jar

@Test
public void testJson() {
ObjectMapper mapper = new ObjectMapper();
String str = "{\"new_terminal\":{\"term\":2,\"rows\":40,\"cols\":185,\"em_dimensions\":{\"w\":7,\"h\":14.96875}}}";
HashMap map;
try {
//readValue到一个原始数据类型.
map = mapper.readValue(str, HashMap.class);
System.out.println("map="+map);
} catch (JsonParseException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
结果如下：map={new_terminal={term=2, rows=40, cols=185, em_dimensions={w=7, h=14.96875}}}

 Map<String,Object> //弄一个这样的map

String string = "{\"new_terminal\":{\"term\":2,\"rows\":40,\"cols\":185,\"em_dimensions\":{\"w\":7,\"h\":14.96875}}}";
    Map<String, Object> map = JSONObject.fromObject(string);
    System.out.println(map);

    map对象就是将Json转换完毕的Map对象结果