Question

 org.codehaus.jackson.map.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) ) through reference chain..

上面是我得到的例外情况，我的pojo中的非原始成员变量无法被读取。在多次搜索之后，我尝试为我的POJO类添加@JsonAutoDetect，并为所有未被识别的字段尝试了@JsonProperty注释。这没用，所以我也尝试了@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})而没有运气。

这是我尝试将对象转换为json的地方：

@Override
public Map<String, String> getChanges(User oldInfo, User newInfo) {
    oldAndNewInfo = new HashMap<String, String>();
    objectWriter = new ObjectMapper().writer().withDefaultPrettyPrinter();
    try {
        oldAndNewInfo.put(objectWriter.writeValueAsString(oldInfo), objectWriter.writeValueAsString(newInfo));
    } catch (Exception e) {
        e.printStackTrace(ps);
    }
    return oldAndNewInfo;
}

有没有人有任何想法？

Answer 1

我认为你应该禁用SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS属性。

保持对象映射器内联（以及最佳实践）的最佳方法是将它们保存在某种模块中。

守卫单身人士，Guice配置，Spring配置，单身人士的一些存储空间。在我的例子中使用了一个受保护的单身人士，但这几乎是文档所说的。

还要记住，xml或json的对象映射器构建起来非常昂贵。如果你做了很多序列化，保存它

public abstract class JsonConfig{

    private JsonConfig(){

    }

    private static final ObjectMapper CONFIGURED_OBJECT_MAPPER;
    private static final JacksonJsonProvider JAX_RS_JSON_PROVIDER;

    static{
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        objectMapper.configure(SerializationFeature.WRAP_ROOT_VALUE, false);
        objectMapper.configure(DeserializationFeature.USE_BIG_DECIMAL_FOR_FLOATS, true);
        objectMapper.configure(SerializationFeature.WRITE_EMPTY_JSON_ARRAYS, true);

        //and just incase you do some web transformaions with jersy or something

        JAX_RS_JSON_PROVIDER = new JacksonJsonProvider(objectMapper);

        CONFIGURED_OBJECT_MAPPER = objectMapper;    
    }

    public static ObjectMapper getObjectMapperInstance(){
        return CONFIGURED_OBJECT_MAPPER;
    }

    public static JacksonJsonProvider getJsonProviderInstance(){
       return return JAX_RS_JSON_PROVIDER
    }
}

将Java Object保存为JSON时出现JsonMappingException

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