[英]Jackson ObjectMapper using custom Serializers and Deserializers
我有一个配置Jackson ObjectMapper的类。 它为我的对象类型添加了一些自定义序列化器和反序列化器,如下所示:
public class JsonMapperFactory {
public static ObjectMapper createObjectMapper() {
final SimpleModule module = new SimpleModule("customerSerializationModule", new Version(1, 0, 0, "static version"));
addCustomDeserializersTo(module);
addCustomSerializersTo(module);
final ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(module);
return objectMapper;
}
private static void addCustomSerializersTo(final SimpleModule module) {
module.addSerializer(DateTime.class, new DateTimeSerializer());
}
private static void addCustomDeserializersTo(final SimpleModule objectMapper) {
objectMapper.addDeserializer(DateTime.class, new DateTimeDeserializer());
}
}
我已经在他们自己的测试类中测试了我的客户序列化器,所以在我对这个JsonMapperFactory
类的测试中,我试图简单地检查创建的ObjectMapper是否具有预期的序列化器(或反序列化器)这可以通过内省ObjectMapper来实现,但它似乎没有任何机制来做到这一点。
有谁知道测试它的好方法?
对于反序列化器,我有以下内容:
private void assertThatObjectMapperUsesCorrectDeserializer(final Class<?> typeClazz, final Class<?> deserializerClazz) throws JsonMappingException {
final DeserializationConfig deserializationConfig = this.objectMapper.getDeserializationConfig();
final JsonDeserializer<Object> deserializer = this.objectMapper.getDeserializerProvider().findTypedValueDeserializer(deserializationConfig, javaTypeFor(typeClazz), null);
assertThat(deserializer, is(instanceOf(deserializerClazz)));
}
private JavaType javaTypeFor(final Class<?> clazz) {
return TypeFactory.type(clazz); //deprecated method :(
}
这是非常详细的,并使用弃用的方法。
我还没有找到一种方法来对序列化器进行类似的测试。 所以我目前使用序列化对象并检查它是否正确序列化(基本上复制了序列化程序测试)
任何想法都非常受欢迎。
从这里提供的答案和评论中,我最近重新设计了类,以便为Module
和ObjectMapper
使用构建器。 这允许我提供模拟并检查是否将正确的(de)序列化程序添加到模块中,然后按预期将模块注册到对象映射器。
对象映射器构建器:
public class ObjectMapperBuilder {
ObjectMapper mapper;
public ObjectMapperBuilder configure(final ObjectMapper mapper) {
this.mapper = mapper;
return this;
}
public ObjectMapperBuilder withModule(final Module module) {
this.mapper.registerModule(module);
return this;
}
public ObjectMapper build() {
return this.mapper;
}
}
模块构建器:
public class SimpleModuleBuilder {
SimpleModule module;
public SimpleModuleBuilder configure(final SimpleModule module) {
this.module = module;
return this;
}
public <X> SimpleModuleBuilder withSerializer(final Class<X> clazz, final JsonSerializer<X> serializer) {
this.module.addSerializer(clazz, serializer);
return this;
}
public <X> SimpleModuleBuilder withDeserializer(final Class<X> clazz, final JsonDeserializer<X> deserializer) {
this.module.addDeserializer(clazz, deserializer);
return this;
}
public SimpleModule build() {
return this.module;
}
}
最后,新的JsonMapperFactory:
public class JsonMapperFactory {
public static ObjectMapper configureObjectMapper(final ObjectMapper mapper, final SimpleModule module) {
final SimpleModuleBuilder modulebuilder = new SimpleModuleBuilder();
final SimpleModule configuredModule = modulebuilder.configure(module)
.withSerializer(DateTime.class, new DateTimeSerializer())
.withDeserializer(DateTime.class, new DateTimeDeserializer())
.build();
final ObjectMapperBuilder objectMapperBuilder = new ObjectMapperBuilder();
return objectMapperBuilder.configure(mapper).withModule(configuredModule).build();
}
}
工厂方法仍在Spring配置中使用,但配置现在实例化空白Module
和ObjectMapper
,然后将它们提供给工厂方法,然后再配置它们。
如果JsonDeserializer
(和DateTimeDeserializer
也是)一个接口,你可以很容易地“JMock”它,将JsonMapperFactory#createObjectMapper
实例传递给JsonMapperFactory#createObjectMapper
,然后期望完全调用你的自定义“serialize”方法; 例如
DateTimeSerializer serializer = context.mock(DateTimeSerializer.class);
DateTimeDeserializer serializer = context.mock(DateTimeDeserializer.class);
ObjectMapper mapper = JacksonMapperFactory.createObjectMapper(deserializer, serializer);
exactly(1).of(jsonDeserializer).serialize(myDateTime,
with(any(JsonGenerator.class),
with(any(SerializerProvider.class)))
作为一个具体的类,你可以改为定义一个新的(测试范围的)De / Serializer来扩展你的自定义DateTime(De)序列化程序,并简单地计算对它的调用:
private static class DateTimeDeserializerWithCounter extends DateTimeDeserializer {
public int counter = 0;
@Override
public DateTime deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
counter++;
return super.deserialize(jsonParser, deserializationContext);
}
}
@Test
public void usageTest(){
//init mapper with the above DateTimeDeserializerWithCounter - see below
mapper.readValue("...", DateTime.class);
Assert.assertEquals(1, deserializer.counter);
}
下面是一个更“以测试为导向”的工厂的快照:
//package visibility, to allow passing different De/Serializers while testing
static ObjectMapper createObjectMapper(JsonDeserializer deserializer, JsonSerializer serializer) {
final SimpleModule module = new SimpleModule("customerSerializationModule", new Version(1, 0, 0, "static version"));
module.addDeserializer(DateTime.class, deserializer);
module.addSerializer(DateTime.class, serializer);
final ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(module);
return objectMapper;
}
//production method: no-args, as in the original version
public static ObjectMapper createObjectMapper() {
return createObjectMapper(new DateTimeDeserializer(), new DateTimeSerializer());
}
希望有所帮助。
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