Spring项目中使用jackson序列化key为对象Map

class A{
　　 //1.注入ObjectMapper，注意这个ObjectMapper是spring全局的。
    @Autowired
    private ObjectMapper objectMapper;
    
    public void setKeyProcessor(){
 　　　

　　　　SimpleModule sm = new SimpleModule();
　　　　//注册序列化，反序列化类。
　　　　sm.addKeySerializer(HistoricTaskInstance.class,new HistoricTaskInstanceKeySerializer());
　　　　sm.addKeyDeserializer(HistoricTaskInstance.class,new HistoricTaskInstanceKeyDeSerializer());
　　　　//注册到ObjectMapper中。
　　　　objectMapper.registerModule(sm);

 } 
} 

static class HistoricTaskInstanceKeySerializer extends JsonSerializer<HistoricTaskInstance> {
    private final  ObjectMapper objectMapper = new ObjectMapper();
    @Override
    public void serialize(HistoricTaskInstance historicTaskInstance, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
        StringWriter writer = new StringWriter();
        objectMapper.writeValue(writer, historicTaskInstance);
        jsonGenerator.writeFieldName(writer.toString());
    }
}

static class SimpleObjectKeyDeSerializer extends KeyDeserializer {
    private final  ObjectMapper objectMapper = new ObjectMapper();
    @Override
    public HistoricTaskInstance deserializeKey(String key, DeserializationContext deserializationContext) throws IOException {
        return objectMapper.readValue(key, HistoricTaskInstance.class);
    }
}

class HistoricTaskInstance{
　　private String name;
   private String address;
}