I am using Spring 4.3.1 and Hibernate 5.1.0 for my webapp.
For Jackson to be able serializing lazy objects I have to add the Hibernate5Module to my default ObjectMapper. This I have done via
#EnableWebMvc
#Configuration
#ComponentScan({ "xxx.controller" })
public class SpringWebConfig extends WebMvcConfigurerAdapter {
#Autowired
SessionFactory sf;
...
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
Hibernate5Module module = new Hibernate5Module(sf);
module.disable(Feature.USE_TRANSIENT_ANNOTATION);
module.enable(Feature.FORCE_LAZY_LOADING);
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.modulesToInstall(module);
converters.add(new MappingJackson2HttpMessageConverter(builder.build()));
super.configureMessageConverters(converters);
}
}
This is working but if it is enabled serializing a byte[] does not work anymore and fails with HTTP Status 500 - Could not write content: No serializer found for class java.io.BufferedInputStream
So my question is how to extend the default ObjectMapper while preserving the default ones?
I have seen somthing preserving the defaults using Spring Boot but I do not use Spring Boot. Any ideas?
As specified in the WebMvcConfigurer.configureMessageConverters javadoc, "If no converters are added, a default list of converters is registered", i.e. you will have to manually add all the default converters if you are using WebMvcConfigurer. Calling 'super.configureMessageConverters(converters)' does nothing if you extend WebMvcConfigurer. Take a look in 'WebMvcConfigurationSupport.addDefaultHttpMessageConverters(...)' to see all the default message converters, you can also extend this class instead of WebMvcConfigurer, with which you get slightly more clarity what happens.
Related
There is something that is not enough clear in this part of Spring Data Rest documentation:
The Spring Data REST exporter executes any discovered
ResourceProcessor`s before it creates the output representation.
For what I have noticed, it's true: ResourceProcessor are invoked during the handling of the request, after the completion of RepositoryEntityController respective method.
It does this by registering a Converter<Entity, Resource> instance
with an internal ConversionService.
I don't understand when it is used this Converter<Entity,Resource>.
This is the component responsible for creating the links to referenced
entities (e.g. those objects under the _links property in the object’s
JSON representation). It takes an #Entity and iterates over its
properties, creating links for those properties that are managed by a
Repository and copying across any embedded or simple properties.
Sure? I noticed that the _links to referenced entities are created in the RepositoryEntityController. I didn't see any other component that builds those links: no ConversionService or Converter are involved.
If your project needs to have output in a different format, however,
it’s possible to completely replace the default outgoing JSON
representation with your own. If you register your own
ConversionService in the ApplicationContext and register your own
Converter, then you can return a Resource
implementation of your choosing.
I don't undestand how is possible to do that.
I have tried to do exactly what is written in the documentation: I have registered my own ConversionService in the ApplicationContext and my own Converter.
I have registered the ConversionService in a custom class that extends RepositoryRestMvcConfiguration:
#Configuration
public class RepositoryConfiguration extends RepositoryRestMvcConfiguration {
#Autowired
AuthorConverter authorConverter;
#Bean(name="conversionService")
public ConversionService getConversionService() {
DefaultFormattingConversionService conversionService = new DefaultFormattingConversionService();
conversionService.addConverter(authorConverter);
return conversionService;
}
#Override
public DefaultFormattingConversionService defaultConversionService() {
return (DefaultFormattingConversionService) getConversionService();
}
}
This is the AuthorConverter:
#Component
public class AuthorConverter implements Converter<Author, Resource> {
#Override
public Resource convert(Author source) {
System.out.println("convert method of class AuthorConverter");
// still to be implemented
return null;
}
}
But the converter is never used: if I go the the /authors url, the JSON is solved as the standard representation, and the "convert" method of the converter is never invoked.
I want to understand (possibly with a working example) how have a custom converter that's being involved in the process of the output representation.
Thanks.
Does this article help?
Source: http://www.baeldung.com/spring-httpmessageconverter-rest
"We can customize the message converters by extending the WebMvcConfigurerAdapter class and overriding the configureMessageConverters method:
#EnableWebMvc
#Configuration
#ComponentScan({ "org.baeldung.web" })
public class WebConfig extends WebMvcConfigurerAdapter {
#Override
public void configureMessageConverters(
List<HttpMessageConverter<?>> converters) {
messageConverters.add(createXmlHttpMessageConverter());
messageConverters.add(new MappingJackson2HttpMessageConverter());
super.configureMessageConverters(converters);
}
private HttpMessageConverter<Object> createXmlHttpMessageConverter() {
MarshallingHttpMessageConverter xmlConverter =
new MarshallingHttpMessageConverter();
XStreamMarshaller xstreamMarshaller = new XStreamMarshaller();
xmlConverter.setMarshaller(xstreamMarshaller);
xmlConverter.setUnmarshaller(xstreamMarshaller);
return xmlConverter;
}
}
I have a Spring Boot app with a REST API, using Jackson for the JSON view configuration. It works great and I can get all the Spring Boot goodness.
However, I need to add an additional REST API that is similar but with different settings. For example, among other things, it needs a different Jackson object mapper configuration because the JSON will look quite a bit different (e.g. no JSON arrays). That is just one example but there are quite a few differences. Each API has a different context (e.g. /api/current and /api/legacy).
Ideally I'd like two MVC configs mapped to these different contexts, and not have to give up any of the automatic wiring of things in boot.
So far all I've been able to get close on is using two dispatcher servlets each with its own MVC config, but that results in Boot dropping a whole bunch of things I get automatically and basically defeats the reason for using boot.
I cannot break the app up into multiple apps.
The answer "you cannot do this with Boot and still get all its magic" is an acceptable answer. Seems like it should be able to handle this though.
There's several ways to achieve this. Based on your requirement , Id say this is a case of managing REST API versions.
There's several ways to version the REST API, some the popular ones being version urls and other techniques mentioned in the links of the comments.
The URL Based approach is more driven towards having multiple versions of the address:
For example
For V1 :
/path/v1/resource
and V2 :
/path/v2/resource
These will resolve to 2 different methods in the Spring MVC Controller bean, to which the calls get delegated.
The other option to resolve the versions of the API is to use the headers, this way there is only URL, multiple methods based on the version.
For example:
/path/resource
HEADER:
X-API-Version: 1.0
HEADER:
X-API-Version: 2.0
This will also resolve in two separate operations on the controller.
Now these are the strategies based on which multiple rest versions can be handled.
The above approaches are explained well in the following: git example
Note: The above is a spring boot application.
The commonality in both these approaches is that there will need to be different POJOS based on which Jackson JSON library to automatically marshal instances of the specified type into JSON.
I.e. Assuming that the code uses the #RestController [org.springframework.web.bind.annotation.RestController]
Now if your requirement is to have different JSON Mapper i.e. different JSON mapper configurations, then irrespective of the Spring contexts you'll need a different strategy for the serialization/De-Serialization.
In this case, you will need to implement a Custom De-Serializer {CustomDeSerializer} that will extend JsonDeserializer<T> [com.fasterxml.jackson.databind.JsonDeserializer] and in the deserialize() implement your custom startegy.
Use the #JsonDeserialize(using = CustomDeSerializer.class) annotation on the target POJO.
This way multiple JSON schemes can be managed with different De-Serializers.
By Combining Rest Versioning + Custom Serialization Strategy , each API can be managed in it's own context without having to wire multiple dispatcher Servlet configurations.
Expanding on my comment of yesterday and #Ashoka Header idea i would propose to register 2 MessageConverters (legacy and current) for custom media types. You can do this like that:
#Bean
MappingJackson2HttpMessageConverter currentMappingJackson2HttpMessageConverter() {
MappingJackson2HttpMessageConverter jsonConverter = new MappingJackson2HttpMessageConverter();
ObjectMapper objectMapper = new ObjectMapper();
// set features
jsonConverter.setObjectMapper(objectMapper);
jsonConverter.setSupportedMediaTypes(Arrays.asList(new MediaType("json", "v2")));
return jsonConverter;
}
#Bean
MappingJackson2HttpMessageConverter legacyMappingJackson2HttpMessageConverter() {
MappingJackson2HttpMessageConverter jsonConverter = new MappingJackson2HttpMessageConverter();
ObjectMapper objectMapper = new ObjectMapper();
// set features
jsonConverter.setObjectMapper(objectMapper);
return jsonConverter;
}
Pay attention to the custom media-type for one of the converters.
If you like , you can use an Interceptor to rewrite the Version-Headers proposed by #Ashoka to a custom Media-Type like so:
public class ApiVersionMediaTypeMappingInterceptor extends HandlerInterceptorAdapter {
#Override
public boolean preHandle(HttpServletRequest request,
HttpServletResponse response, Object handler) throws Exception {
try {
if(request.getHeader("X-API-Version") == "2") {
request.setAttribute("Accept:","json/v2");
}
.....
}
}
This might not be the exact answer you were looking for, but maybe it can provide some inspiration. An interceptor is registered like so.
If you can live with a different port for each context, then you only have to overwrite the DispatcherServletAutoConfiguration beans. All the rest of the magic works, multpart, Jackson etc. You can configure the Servlet and Jackson/Multipart etc. for each child-context separately and inject bean of the parent context.
package test;
import static org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration.DEFAULT_DISPATCHER_SERVLET_BEAN_NAME;
import static org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration.DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.context.embedded.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
import org.springframework.web.servlet.DispatcherServlet;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
#Configuration
#EnableAutoConfiguration(exclude = {
Application.Context1.class,
Application.Context2.class
})
public class Application extends WebMvcConfigurerAdapter {
#Bean
public TestBean testBean() {
return new TestBean();
}
public static void main(String[] args) {
final SpringApplicationBuilder builder = new SpringApplicationBuilder().parent(Application.class);
builder.child(Context1.class).run();
builder.child(Context2.class).run();
}
public static class TestBean {
}
#Configuration
#EnableAutoConfiguration(exclude = {Application.class, Context2.class})
#PropertySource("classpath:context1.properties")
public static class Context1 {
#Bean(name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
DispatcherServlet dispatcherServlet() {
DispatcherServlet dispatcherServlet = new DispatcherServlet();
// custom config here
return dispatcherServlet;
}
#Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)
ServletRegistrationBean dispatcherServletRegistration() {
ServletRegistrationBean registration = new ServletRegistrationBean(dispatcherServlet(), "/test1");
registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
// custom config here
return registration;
}
#Bean
Jackson2ObjectMapperBuilder jackson2ObjectMapperBuilder(TestBean testBean) {
System.out.println(testBean);
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
// custom config here
return builder;
}
}
#Configuration
#EnableAutoConfiguration(exclude = {Application.class, Context1.class})
#PropertySource("classpath:context2.properties")
public static class Context2 {
#Bean(name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
DispatcherServlet dispatcherServlet() {
DispatcherServlet dispatcherServlet = new DispatcherServlet();
// custom config here
return dispatcherServlet;
}
#Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)
ServletRegistrationBean dispatcherServletRegistration() {
ServletRegistrationBean registration = new ServletRegistrationBean(dispatcherServlet(), "/test2");
registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
// custom config here
return registration;
}
#Bean
Jackson2ObjectMapperBuilder jackson2ObjectMapperBuilder(TestBean testBean) {
System.out.println(testBean);
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
// custom config here
return builder;
}
}
}
The context1/2.properties files currently only contain a server.port=8080/8081 but you can set all the other spring properties for the child contexts there.
In Spring-boot ypu can use different profiles (like dev and test).
Start application with
-Dspring.profiles.active=dev
or -Dspring.profiles.active=test
and use different properties files named application-dev.properties or application-test.properties inside your properties directory.
That could do the problem.
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've got something like this in my controller:
#RequestMapping
#ResponseBody
public HttpEntity<PagedResources<PromotionResource>> promotions(
#PageableDefault(size = RestAPIConfig.DEFAULT_PAGE_SIZE, page = 0) Pageable pageable,
PagedResourcesAssembler<Promotion> assembler
){
PagedResources<PromotionResource> r = assembler.toResource(this.promoService.find(pageable), this.promoAssembler);
return new ResponseEntity<PagedResources<PromotionResource>>(r, HttpStatus.OK);
}
If i navigate to the URL mapped to that controller method i get a 500 error with a root cause of:
com.sun.istack.internal.SAXException2: unable to marshal type "commerce.api.rest.resources.PromotionResource " as an element because it is missing an #XmlRootElement annotation
If i throw a #XmlRootElement annotation on my resource it becomes this error:
com.sun.istack.internal.SAXException2: unable to marshal type "commerce.api.rest.resources.PromotionResource " as an element because it is not known to this context.
Everything is fine if the accept header is application/json or application/hal+json. The problem is caused only when the client (in this case chrome) is looking for application/xml (which makes sense as HATEOAS is following the clients requests. I'm using spring boot's #EnableAutoConfiguration which is adding the XML message converter to the list and thus enabling XML content types.
I'm guessing i have at least 2 options:
1. fix the jaxb error
2. remove xml as a supported content type
not sure how to do either, or maybe there's another option.
If you don't actually want to produce XML try using the produces attribute of the #RequestMapping annotation. Something like: #RequestMapping(produces=MediaType.APPLICATION_JSON_VALUE)
Alternatively you could exclude jaxb from you classpath or look at adding your own org.springframework.boot.autoconfigure.web.HttpMessageConverters bean to take complete control of the registered HttpMessageConverter's. See WebMvcConfigurationSupport.addDefaultHttpMessageConverters to see what Spring will add by default.
Not sure this is a good technique, and it looks like in 1.1.6 there's a different approach. Here's what i did:
#Configuration
public class WebMVCConfig extends WebMvcAutoConfiguration.WebMvcAutoConfigurationAdapter {
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
//Remove the Jaxb2 that is automatically added because some other dependency brings it into the classpath
List<HttpMessageConverter<?>> baseConverters = new ArrayList<HttpMessageConverter<?>>();
super.configureMessageConverters(baseConverters);
for(HttpMessageConverter<?> c : baseConverters){
if(!(c instanceof Jaxb2RootElementHttpMessageConverter)){
converters.add(c);
}
}
}
}
if you don't want to support XML converter, you can extend spring WebMvcConfigurer to exclude XML message converters.
#Configuration
public class WebMVCConfig extends WebMvcAutoConfiguration.WebMvcAutoConfigurationAdapter {
#Override
public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.removeIf(c -> c instanceof AbstractXmlHttpMessageConverter<?>);
}
}
i am working on BIRT reporting tool. which is need to called by spring MVC.
i got one example from spring which is here. in this example, configuration is done via bean. can anyone help me convert this configuration in to xml based configuration ?
#EnableWebMvc
#ComponentScan({ "org.eclipse.birt.spring.core","org.eclipse.birt.spring.example" })
#Configuration
public class BirtWebConfiguration extends WebMvcConfigurerAdapter {
#Override
public void addViewControllers(ViewControllerRegistry registry) {
registry.addViewController("/reports").setViewName("birtView");
}
#Bean
public BirtView birtView() {
BirtView bv = new BirtView();
// bv.setReportFormatRequestParameter("ReportFormat");
// bv.setReportNameRequestParameter("ReportName");
bv.setBirtEngine(this.engine().getObject());
return bv;
}
#Bean
public BeanNameViewResolver beanNameResolver() {
BeanNameViewResolver br = new BeanNameViewResolver();
return br;
}
#Bean
protected BirtEngineFactory engine() {
BirtEngineFactory factory = new BirtEngineFactory();
return factory;
}
}
I wants a similar configuration in xml file.
There's really no tool for extracting Spring annotations to Spring bean context xml file. You'll have to do it by hand, shouldn't be too hard as all the Spring annotations functionality can be duplicated into Spring context xml tags.
if you want to use spingmvc, so no need the configuration files.
my solution is that in Birt Script i call the impl java file like this :
sampleService = new Packages.com.example.warlock.service.SampleServiceImpl();
pojo = new Packages.com.example.warlock.entity.Sample();
iterator = sampleService.getSamples().iterator();
because my SampleService is a interface and SampleServiceImpl is impl java, the two java file are not config as #Bean.
At first i want to get the data from ModelMap but failed, so i skip the controller and straight to call Service, then final call the DAO to get the Data from DB