我希望Jackson使用以下构造函数反序列化一个类:
public Clinic(String name, Address address)
反序列化第一个参数很容易。问题是地址被定义为:
public class Address {
private Address(Map<LocationType, String> components)
...
public static class Builder {
public Builder setCity(String value);
public Builder setCountry(String value);
public Address create();
}
}
并且构造如下:new Address.Builder().setCity("foo").setCountry("bar").create();
有没有办法从杰克逊获得键值对,以便自己构建地址?或者,有没有办法让杰克逊使用Builder类本身?
只要你使用杰克逊2+,那么现在有built in support for this。
首先,您需要将此注释添加到Address
类:
@JsonDeserialize(builder = Address.Builder.class)
然后你需要将这个注释添加到你的Builder
类:
@JsonPOJOBuilder(buildMethodName = "create", withPrefix = "set")
如果您乐意将Builder的create方法重命名为build,并且Builder的setter前缀为with而不是set,则可以跳过此第二个注释。
完整示例:
@JsonDeserialize(builder = Address.Builder.class)
public class Address
{
private Address(Map<LocationType, String> components)
...
@JsonPOJOBuilder(buildMethodName = "create", withPrefix = "set")
public static class Builder
{
public Builder setCity(String value);
public Builder setCountry(String value);
public Address create();
}
}
@Rupert Madden-Abbott的答案很有效。但是,如果您有非默认构造函数,例如,
Builder(String city, String country) {...}
然后你应该注释如下参数:
@JsonCreator
Builder(@JsonProperty("city") String city,
@JsonProperty("country") String country) {...}
我最终使用@JsonDeserialize实现了这个,如下所示:
@JsonDeserialize(using = JacksonDeserializer.class)
public class Address
{...}
@JsonCachable
static class JacksonDeserializer extends JsonDeserializer<Address>
{
@Override
public Address deserialize(JsonParser parser, DeserializationContext context)
throws IOException, JsonProcessingException
{
JsonToken token = parser.getCurrentToken();
if (token != JsonToken.START_OBJECT)
{
throw new JsonMappingException("Expected START_OBJECT: " + token, parser.getCurrentLocation());
}
token = parser.nextToken();
Builder result = new Builder();
while (token != JsonToken.END_OBJECT)
{
if (token != JsonToken.FIELD_NAME)
{
throw new JsonMappingException("Expected FIELD_NAME: " + token, parser.getCurrentLocation());
}
LocationType key = LocationType.valueOf(parser.getText());
token = parser.nextToken();
if (token != JsonToken.VALUE_STRING)
{
throw new JsonMappingException("Expected VALUE_STRING: " + token, parser.getCurrentLocation());
}
String value = parser.getText();
// Our Builder allows passing key-value pairs
// alongside the normal setter methods.
result.put(key, value);
token = parser.nextToken();
}
return result.create();
}
}
在这种情况下适合我的解决方案(我使用“Lombok”构建器注释)。
@Getter
@Builder(builderMethodName = "builder")
@NoArgsConstructor(access = AccessLevel.PRIVATE)
@AllArgsConstructor(access = AccessLevel.PRIVATE)
@JsonAutoDetect(
fieldVisibility = JsonAutoDetect.Visibility.ANY,
creatorVisibility = JsonAutoDetect.Visibility.ANY
)
我希望对你也有用。
目前还没有对构建器模式的支持,虽然它已经被要求很久了(最后Jira问题http://jira.codehaus.org/browse/JACKSON-469被提交) - 如果有足够的需求,可以添加1.8版本(确保投票给吉拉!)。这是一个合理的附加功能,只是延迟了开发人员的时间。但我认为这将是一个很好的补充。