我使用
Jackson
将 JSON 反序列化为不可变的自定义 Java 对象。这是课程:
final class DataPoint {
private final int count;
private final int lower;
private final int median;
private final int upper;
@JsonCreator
DataPoint(
@JsonProperty("count") int count,
@JsonProperty("lower") int lower,
@JsonProperty("median") int median,
@JsonProperty("upper") int upper) {
if (count <= 0) {
throw new IllegalArgumentException("...");
}
this.count = count;
this.lower = lower;
this.median = median;
this.upper = upper;
}
// getters...
}
这是我反序列化的 JSON:
{
"count": 3,
"lower": 2,
"median": 3,
"upper": 4
}
效果很好。现在我破坏 JSON,即复制
lower
属性:
{
"count": 4,
"lower": 2,
"lower": 3,
"median": 4,
"upper": 5
}
现在我得到了
count == 4
和lower == 3
。相反,我希望 Jackson
反序列化失败,因为 JSON 中存在重复的属性 (lower
)。
这是反序列化代码:
String json = "..."; // the second JSON
ObjectMapper mapper = new ObjectMapper().enable(
DeserializationFeature.FAIL_ON_MISSING_CREATOR_PROPERTIES,
DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES,
DeserializationFeature.FAIL_ON_READING_DUP_TREE_KEY)
.disable(DeserializationFeature.ACCEPT_FLOAT_AS_INT);
DataPoint data = mapper.readValue(json, DataPoint.class);
各位,在反序列化具有重复属性键的 JSON 时,我可以使
Jackson
失败吗?
非常感谢你们,伙计们!
您可以启用
STRICT_DUPLICATE_DETECTION
以使解析器在存在重复属性时抛出 Exception
,例如:
String s = "{\"count\": 4,\"lower\": 2,\"lower\": 3,\"median\": 4,\"upper\": 5}";
ObjectMapper mapper = new ObjectMapper();
mapper.enable(JsonParser.Feature.STRICT_DUPLICATE_DETECTION);
JsonNode readTree = mapper.readTree(s);
System.out.println(readTree.toString());
这将抛出以下异常:
Exception in thread "main" com.fasterxml.jackson.core.JsonParseException: Duplicate field 'lower'
这是文档。
对于 Spring,此配置使用
STRICT_DUPLICATE_DETECTION
可以正常工作
@Configuration
public class JacksonConfig {
@Bean
public ObjectMapper objectMapper() {
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.enable(JsonParser.Feature.STRICT_DUPLICATE_DETECTION);
return objectMapper;
}
}