Java's Jackson converts json string into generic List

Jackson, I feel, is the fastest framework for converting between Java and Json. Of course, Google's Gson is also very good, but based on the performance tests of people on the Internet, it seems that Jackson is faster.

Jackson can handle the conversion between general JavaBean and Json by simply using the readValue and writeValueAsString methods of the ObjectMapper object. But if you want to convert a complex type Collection such as List, you need to first deserialize the complex type into a generic Collection Type.

If it is ArrayList, then use ObjectMapper’s getTypeFactory().constructParametricType(collectionClass, elementClasses);

If it is HashMap, then ObjectMapper’s getTypeFactory().constructParametricType( HashMap.class,String.class, YourBean.class);

public final ObjectMapper mapper = new ObjectMapper(); 
  
public static void main(String[] args) throws Exception{ 
  JavaType javaType = getCollectionType(ArrayList.class, YourBean.class); 
  List<YourBean> lst = (List<YourBean>)mapper.readValue(jsonString, javaType); 
}
 
  /**  
  * 获取泛型的Collection Type 
  * @param collectionClass 泛型的Collection  
  * @param elementClasses 元素类  
  * @return JavaType Java类型  
  * @since 1.0  
  */ 
public static JavaType getCollectionType(Class<?> collectionClass, Class<?>... elementClasses) {  
  return mapper.getTypeFactory().constructParametricType(collectionClass, elementClasses);  
}

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