I am using Spring Boot framework and trying to create a structure where the developer can only return org.json.JSONObject instance. I have this endpoint declaration.
#RequestMapping(path = "/hello", method = RequestMethod.POST)
#ResponseBody
public org.json.JSONObject hello(HttpServletRequest request, HttpServletResponse response) throws IOException
This always returns {"empty":false} because Jackson used by the framework does not know how to serialize the org.json instance. I am trying to tell Jackson how to serialize the org.json instance by using the following dependency.
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-json-org</artifactId>
<version>2.13.0</version>
</dependency>
But I cannot get it work unless I change the return type to Map value which is not possible. Using
ObjectMapper mapper = JsonMapper.builder()
.addModule(new JsonOrgModule())
.build()
does not help. Is there a global ObjectMapper object that is used by Spring Boot where I can register the JsonOrgModule at the application startup? How can I use org.json.JSONObject return type using Spring Boot framework.
Thanks!
As per Spring Boot docs 4.3 Customize the Jackson ObjectMapper section:
Any beans of type com.fasterxml.jackson.databind.Module are
automatically registered with the auto-configured
Jackson2ObjectMapperBuilder and are applied to any ObjectMapper
instances that it creates. This provides a global mechanism for
contributing custom modules when you add new features to your
application.
Therefore, if you provide a #Bean of type JsonOrgModule it will be automatically applied to the default ObjectMapper created at startup.
For exmaple:
#SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
#Bean
public JsonOrgModule jsonOrgModule() {
return new JsonOrgModule();
}
}
#SpringBootTest
class ObjectMapperTests {
#Autowired
ObjectMapper defaultObjectMapper;
#Test
void defaultObjectMapperShouldWriteJsonObject() throws JSONException, JsonProcessingException {
// Given
var jsonObject = new JSONObject().put("username", "eHayik");
// When
var json = defaultObjectMapper.writeValueAsString(jsonObject);
// Then
assertThat(json).isEqualTo("{\"username\":\"eHayik\"}");
}
}
Related
I'm trying to deserialise an a JSON input using a class that is annotated with #JsonComponent. However, even though I manually register this class, it is still not invoked when I call the endpoint with the input. I use openapi-generator-maven-plugin for generating controllers and aspectj for compile-time weaving. Can this interfere with the objects being recognised?
Note: The same setup works in a different poc application that I made but not this one. The main difference I see is the code generation. Hence I'm wondering if using the open-api-generation interferes with the Deserializer being recognised during the call to the Controller
#JsonComponent
public class UserDeserializer extends JsonDeserializer<User> {
#Override
public User deserialize (JsonParser jsonParser, DeserializationContext
deserializationContext) throws IOException {
log.info("***********INVOKED***************");
TreeNode treeNode = jsonParser.getCodec().readTree(jsonParser);
ObjectMapper objectMapper = new ObjectMapper();
//Some logic here
}
}
Config class has
#Bean
public Module userDeserializer() {
SimpleModule module = new SimpleModule();
module.addDeserializer(User.class, new UserDeserializer());
return module;
}
This is a common error in Spring when tries to transform automatically an entity object whit some hibernate proxys but i dont't know how to load Jackson DataType Hibernate5 module in Spring cloud functions gcp adapter.
#SpringBootApplication
#Log4j2
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
#Bean
public WebMvcConfigurer corsConfigurer() {
log.info("configurando cors");
return new WebMvcConfigurer() {
#Override
public void addCorsMappings(CorsRegistry registry) {
registry.addMapping("/**").allowedOrigins("*");
}
};
}
#Bean
public Module datatypeHibernateModule() {
log.info("Cargando modulo hibernate jackson");
return new Hibernate5Module();
}
}
If i use the same code whit normal Spring boot project the module works but in this case i found on the log the adapter don't used Jackson and they implements Gson.
at com.google.gson.Gson.toJson(Gson.java:638)
at com.google.gson.Gson.toJson(Gson.java:618)
at org.springframework.cloud.function.json.GsonMapper.toJson(GsonMapper.java:70)
This is the entire log file
My first workaround is change the Page object for String and use manually jackson mapper.
public class ObtenerEstados implements Function<Void, String> {
#Autowired
private EstadoService estadoService;
#SneakyThrows
#Override
public String apply(Void unused) {
Page<Estado> page = estadoService.buscarTodos(0, 33);
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new Hibernate5Module());
String objectAsString = objectMapper.writeValueAsString(page);
return objectAsString;
}
}
I created two branches on the Github repository
functions (this branch have the bug)
function-jackson-hibernate5 (this branch have the workaround)
If you haved already installed Docker and Docker Compose you can reproduce the bug easy.
Follow the next steps:
git clone https://github.com/ripper2hl/sepomex.git
cd sepomex
git checkout -b dev origin/functions
docker-compose pull db
docker-compose up -d db
export spring_profiles_active=local
mvn -Pgcp function:run
And execute with a curl or any REST client
curl http://localhost:8080/
I know the alternative for use a DTO object but i prefer not use this option
So whenever Gson is on the classpath it is given priority and of course with Google that is the case. Please set spring.http.converters.preferred-json-mapper=jackson property to force Jackson.
Finally i fixed with this fragment of code
#SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
#Bean
public JsonMessageConverter jsonMessageConverter() {
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new Hibernate5Module());
JacksonMapper jacksonMapper = new JacksonMapper(objectMapper);
return new JsonMessageConverter(jacksonMapper);
}
}
The documentation explain Gson is the default MessageConverter but it's not be clear how to change(more easy) gson to jackson.
https://docs.spring.io/spring-cloud-function/docs/current/reference/html/spring-cloud-function.html#_provided_messageconverters
I'm running into a scenario where I need to define a one-off #FeignClient for a third party API. In this client I'd like to use a custom Jackson ObjectMapper that differs from my #Primary one. I know it is possible to override spring's feign configuration defaults however it is not clear to me how to simply override the ObjectMapper just by this specific client.
Per the documentation, you can provide a custom decoder for your Feign client as shown below.
Feign Client Interface:
#FeignClient(value = "foo", configuration = FooClientConfig.class)
public interface FooClient{
//Your mappings
}
Feign Client Custom Configuration:
#Configuration
public class FooClientConfig {
#Bean
public Decoder feignDecoder() {
HttpMessageConverter jacksonConverter = new MappingJackson2HttpMessageConverter(customObjectMapper());
HttpMessageConverters httpMessageConverters = new HttpMessageConverters(jacksonConverter);
ObjectFactory<HttpMessageConverters> objectFactory = () -> httpMessageConverters;
return new ResponseEntityDecoder(new SpringDecoder(objectFactory));
}
public ObjectMapper customObjectMapper(){
ObjectMapper objectMapper = new ObjectMapper();
//Customize as much as you want
return objectMapper;
}
}
follow #NewBie`s answer, i can give the better one...
#Bean
public Decoder feignDecoder() {
return new JacksonDecoder();
}
if you want use jackson message converter in feign client, please use JacksonDecoder, because SpringDecoder will increase average latency of feignclient call in production.
<!-- feign-jackson decoder -->
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-jackson</artifactId>
<version>10.1.0</version>
</dependency>
Define a custom decoder as below, annotated with #Configuration and set as parameter for the feign client interface, configuration = CustomFeignClientConfig.class
#Configuration
public class CustomFeignClientConfig {
#Bean
public Decoder feignDecoder() {
return (response, type) -> {
String bodyStr = Util.toString(response.body().asReader(Util.UTF_8));
JavaType javaType = TypeFactory.defaultInstance().constructType(type);
return new ObjectMapper().readValue( bodyStr, javaType);
};
}
}
#NewBie's answer has serious performance problems. During the new HttpMessageConverters process, loadclass will be performed, resulting in a large number of thread block. If you have used this code, please modify it as follows:
ObjectFactory<HttpMessageConverters> objectFactory = () -> new HttpMessageConverters(jacksonConverter);
change to
HttpMessageConverters httpMessageConverters = new HttpMessageConverters(jacksonConverter);
ObjectFactory<HttpMessageConverters> objectFactory = () -> httpMessageConverters;
You can use JMeter and Arthas to reproduce this phenomenon, and the modified program has been greatly improved.
Back-end, Spring boot project(v1.3.0.RELEASE), supply Rest JSON Api to fron-end, just now encountered an error:
Infinite recursion (StackOverflowError)
I decide to change to a custom FastJsonHttpMessageConverter, and code is below
#Bean
public HttpMessageConverter httpMessageConverter() {
FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
return fastJsonHttpMessageConverter;
}
but it does not work, in real it uses a default HttpMessageConverter. Although does not have above error, the output is not as I expected. e.g.
suppliers: [
{
$ref: "$.value"
}
]
Now change above code
#Bean
public HttpMessageConverter mappingJackson2HttpMessageConverter() {
FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
return fastJsonHttpMessageConverter;
}
This time it works, I want to know why the method name have to be mappingJackson2HttpMessageConverter? If use another method name how to configure it?
After seeing this offical document, I know how to customize converters.
#Bean
public HttpMessageConverters customConverters() {
HttpMessageConverter<?> additional = new FastJsonHttpMessageConverter();
return new HttpMessageConverters(additional);
}
A Revise to my main post, actually below code does not work.
#Bean
public HttpMessageConverter mappingJackson2HttpMessageConverter() {
FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
return fastJsonHttpMessageConverter;
}
Spring boot never enter this method if you set breakpoint inside it.
And below code also works.
#SpringBootApplication
public class FooApplication extends WebMvcConfigurerAdapter {
public static void main(String[] args) {
SpringApplication.run(FooApplication.class, args);
}
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
super.configureMessageConverters(converters);
converters.add(new FastJsonHttpMessageConverter());
}
}
Spring boot says (https://docs.spring.io/spring-boot/docs/current/reference/html/howto-spring-mvc.html#howto-customize-the-responsebody-rendering):
If a bean you add is of a type that would have been included by default anyway (like MappingJackson2HttpMessageConverter for JSON conversions) then it will replace the default value.
The bean you are adding is not of the same type, so the above does not happen. Your converter goes somewhere in the list of converters (probably the end), and the first suitable converter (the old one) does the job.
Beans produced by the Java configuration have the name of the method, so when you create a second bean named mappingJackson2HttpMessageConverter, it overrides the one created by spring boot's JacksonHttpMessageConvertersConfiguration and takes it place.
Instead of adding a converter bean, you might prefer to override the whole list of converters:
As in normal MVC usage, any WebMvcConfigurerAdapter beans that you provide can also contribute converters by overriding the configureMessageConverters method,
I have a spring boot application that serves my jersey based api. I have a requirement to have the services layer serve blob data to a client as a stream. I wrote a servlet to do that and configured it as follows.
#Bean
public ServletRegistrationBean servletRegistrationBean(){
return new ServletRegistrationBean(new BlobReaderServlet(),"/blobReader/*");
}
However, in the servlet code I can't seem to inject any components (they are all null). I need to inject a component that actually loads the blob data from the database.
#WebServlet(name = "BlobReaderServlet",
urlPatterns = {"/blobreader"})
#Component
public class BlobReaderServlet extends HttpServlet {
Logger logger = Logger.getLogger(this.getClass().getName());
#Inject
DocumentLoaderComponent blobLoader;
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
I strongly suspect the servlet isn't a spring managed component after all and dependency injection isn't working. How can I get access to a component from the context?
UPDATE
It was much simpler than I thought.
#Override
public void init() throws ServletException {
ApplicationContext ac = (ApplicationContext) getServletConfig().getServletContext().getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
this.documentBlob = (DocumentBlob) ac.getBean("documentBlobBean");
}
You are correct that your servlet isn't a Spring managed bean. That is because you are instantiating the instance directly (i.e., calling new BlobReaderServlet() in your bean method). Another solution is to change your configuration class as follows:
#Bean
public ServletRegistrationBean servletRegistrationBean(){
return new ServletRegistrationBean(blobReaderServlet(),"/blobReader/*");
}
#Bean
public BlobReaderServlet blobReaderServlet(){
return new BlobReaderServlet();
}
This will allow Spring to manage the instance and perform autowiring on it.