I'm developing a web application using Spring MVC; it works as follows:
a JSON request is created from a model object (a POJO)
it's sent to an external server that exposes some APIs
a JSON response is received by the controller
I need to figure out which is the best way to serialize and deserialize JSON in a Java web application. At first I was using Gson but then I began to wonder if it was the right choice.
Is it possible to serialize and deserialize JSON to/from model
object using #RestController annotation? How does it works? I only find examples of how to create a rest service, in this sense
What is the best practice in this case? RestController? Gson? Jackson? Other?
N.B. My JsonResponse object has a generic field because the responses are all the same except that for a value. An example:
AccountRequest.class
public class AccountRequest() {
private String jsonrpc;
private String method;
private Map<String, Object> params;
private int id;
//constructor, getters and setters
}
JsonResponse.class
public class JsonResponse<T> {
private String jsonrpc;
private T result;
private String id;
//constructor, getters and setters
}
LoginResult.class
public class LoginResult {
private String token;
private String product;
private String error;
private Date lastLoginDate;
//constructor, getters and setters
}
MyController.class
#Controller
public class LoginController {
String response;
[...]
#RequestMapping(value = "/login", method = RequestMethod.POST)
public ModelAndView doLogin(#ModelAttribute("user") User user) {
[...]
//???
[...]
}
}
I open connection, send request and save the response in response String in MyController class. User parameter is annotated with #ModelAttribute to retrive the User object created by the showLoginForm() method.
Using Gson I know how to serialize request from my model object:
AccountRequest accountRequest = new AccountRequest();
accountRequest.setJsonrpc("2.0");
accountRequest.setMethod("method");
accountRequest.setParams(params);
accountRequest.setId(1);
String gson = new Gson().toJson(accountRequest);
JSONObject accountRequestJson = new JSONObject(gson);
And how to deserialize response in my model object:
Type jsonType = new TypeToken<JsonResponse<LoginResult>>() {}.getType();
JsonResponse<LoginResult> jsonResponse = new Gson().fromJson(response, jsonType);
The response is now saved into jsonResponse object, and I can put it in my ModelAndView.
Now, how can I deserialize it in my model object using #RestController and Jackson? Can you confirm it's the better method to do that? Can you post an example?
I hope it's not a silly question.
Thanks in advance!
Related
For some reason java can't map DTO with requestBody and all values are default ones, as for request it works, with payload for ex. "{"productId":1,"commitment":6,"returnMonths":"2"}"
DTO
#Data
public class Request {
private int productId;
private int commitment;
private String returnMonths;
// contructers
}
Controller :
#PostMapping(value = "/calculate", consumes = MediaType.APPLICATION_JSON_VALUE)
#ResponseBody
public String calculatePrice(#RequestBody Request request) {
productService.calculatePrice(request);
return "Success";
}
front request:
submit: async function() {
let request = {
productId: this.productSelected,
commitment: this.optionSelected,
returnMonths: this.input
};
let data = await getCalculation(request);
console.log(data);
}
DTO maps as:
productId : 0
commitment : 0
returnMonths : null
Tried an exact copy of your code and it worked when tested with Postman. This makes me think it's either something to do with the FE or maybe some issue in the service. I'd check if the Frontend really sends the data.
Try to annotation Request class with #AllArgsConstructor like:
#AllArgsConstructor
#Data
public class Request {
private int productId;
private int commitment;
private String returnMonths;
}
If your request body contains properties that is date such as LocalDateTime, make sure to format it in your DTO using #JsonFormat(pattern="") respecting the input value.
Can someone please help me how to get a JSON String in a Webservice. I's sending JSON to my /api/register that looks like:
{"name":"MyName","surname":"MySurename","email":"mail#asd.de","street":"MyStreet","number":"3","zip":"12345","city":"myCity","pass":"myPassword"}
Here is my register.java file:
#Path("/register")
#Stateless
public class RegisterWS {
#EJB
UserBS userBS;
#POST
#Consumes(MediaType.APPLICATION_JSON)
public void createUser(){
// code to get data from json
userBS.createUser(name, surename, email, adress, number, zip, city, password);
}
}
My AngularJS Controller and Service. The Data comes from a form, that is parsed to a JSON object.
app.service('RegisterService', function ($http) {
return {
registerUser : function(user) {
$http.post('http://localhost:8080/myApp/api/register')
.success(function (user) {
return user;
})
.error(function (data) {
// failed
});
}
}
});
app.controller('RegisterCtrl', function($scope, RegisterService) {
$scope.register = function(){
RegisterService.registerUser(angular.toJson($scope.user));
}
});
You should have a POJO, which maps to the received JSON object, for example a User class. In this case this would be a very simple Java Bean, with mostly String properties for each field in the JSON.
#XmlRootElement
public class User {
String name;
String surname;
String email;
String street;
Integer number;
String zip;
String city;
String pass;
}
Of course you would use private fields, with getters and setters, but I did not want to add clutter. By the way the #XmlRootElement is a JAXB annotation, and JAX-RS uses JAXB internally.
After you have this, you just need to change your method like this
#POST
#Consumes(MediaType.APPLICATION_JSON)
public void createUser(User user) {
...
}
You should not need to change anything on the AngularJS side, as the default for the $http.post method is JSON communication.
For your Java code, you have to add a User POJO, I dont know if you will use some persistence API or not, so the user POJO must implement serializable to output user object as JSON.
Here's a an example of REST app with EJB ... : http://tomee.apache.org/examples-trunk/rest-on-ejb/README.html
For your client app, you need to specify the content type : "Content-Type" = "application/json"
See this questions: change Content-type to "application/json" POST method, RESTful API
I'm using AndroidAnnotations to build a Rest for an Android Application.
On the Serverside im using PHP, which send a json looking like :
{"tag":"register","success":0,"error":2,"msg":"User already existed","body":[]}
I have two POJOS :
User.java:
public class User implements Serializable {
private String name;
private String email;
private String password;
//getter and setter Methods
}
Response.java:
public class RegistrationResponse implements Serializable {
private String tag;
private int success;
private int error;
private String msg;
private String body;
//getter and setter Methods
}
Rest Client:
#Rest(rootUrl = "http://my.domain.com", converters = {
MappingJacksonHttpMessageConverter.class,
StringHttpMessageConverter.class, GsonHttpMessageConverter.class }, interceptors = { MyInterceptor.class })
public interface RestClient extends RestClientErrorHandling {
#Post("/user/register/{name}/{email}/{pass}")
#Accept(MediaType.APPLICATION_JSON_VALUE)
Response sendUserRegistration(User user, String name, String email,
String pass);
RestTemplate getRestTemplate();
}
Activity.java:
//User and Response are POJOs
Response result = RestClient.sendUserRegistration(user,
user.getName(),user.getEmail(),user.getPassword());
But i got an Null Pointer Exception error on Activity.java. But if i change the return value of "sendUserRegistration" function to String all work. So my "Response" POJO seems not to be converted from AndroidAnnotations.
How can i convert the Rest Response to my "Response"-POJO using AndroidAnnotations?
You don't need to return the entire response object per rest call, just set the response to your custom object. Or you can also return a JsonObject also and use gson to convert it later on.
#Rest(rootUrl = "http://my.domain.com", converters = {
MappingJacksonHttpMessageConverter.class,
StringHttpMessageConverter.class, GsonHttpMessageConverter.class }, interceptors = { MyInterceptor.class })
public interface RestClient extends RestClientErrorHandling {
#Post("/user/register/{name}/{email}/{pass}")
#Accept(MediaType.APPLICATION_JSON_VALUE)
User sendUserRegistration(User user, String name, String email,
String pass);
RestTemplate getRestTemplate();
}
then just simply call
User newUser = RestClient.sendUserRegistration(user,
user.getName(),user.getEmail(),user.getPassword());
AA relies on Spring Android RestTemplate to make the rest call. And in order to build requests and handle responses this lib uses converters. And to know which converter the RestTemplate should use, it checks the content-type response header.
As MappingJacksonHttpMessageConverter and GsonHttpMessageConverter handles only http response with content-type=application/json and your result is converted to string, I'm pretty sure you forgot to set this header in your php server. So it send the default one (ie: text/plain) which is only handle by StringHttpMessageConverter.
Also, the body field is an object in your json example, but in your POJO you declared it as a String. So parsing will fail on this point.
I am trying to make a post call to a controller, but the object I am expecting contains a Set datatype and I am unsure how the post data should look.
Models:
public class Notebook{
private string name;
private Set<Todo> todos;
}
public class Todo{
private String name;
}
Controller
#RequestMapping(method = RequestMethod.POST)
public void createNotebook(Notebook q){
questionnaireService.saveOrUpdateNotebook(q);
}
Currently I have tried posting like the example below:
curl --data "name=some notebook&todos[0].name=todo1&todos[1].name=todo2" http://localhost:8080/api/notebook
Doesn't seem to work. Anyone have experience with Sets?
You should qualify Notebook q with #RequestBody annotation so that the request can be mapped to an object of type Notebook. More about the format of the input data and the converters in Spring MVC doc: Mapping the request body with the #RequestBody annotation.
We send data from the front-end in JSON format and use Jackson JSON to convert it to the Java object. If you go that route, you can directly declare the todos as Set<String> and the input would be
{
name: "some notebook",
todos: ["todo1", "todo2"]
}
I just took the tutorial over at Spring.io http://spring.io/guides/gs/rest-service/ and created a simple rest service. But, does anybody know how I can return multiple objects in JSON format? If I for instance have a person class with a name and an id, how can I add three persons to /persons?
You can use the #ResponseBody annotation and just return whatever you want, providing that those objects can be jsonized.
For example, you can have a bean like this:
#Data
public class SomePojo {
private String someProp;
private List<String> someListOfProps;
}
and then in your controller you can have:
#ResponseBody
#RequestMapping("/someRequestMapping")
public List<SomePojo> getSomePojos(){
return Arrays.<String>asList(new SomePojo("someProp", Arrays.<String>asList("prop1", "prop2"));
}
and Spring by default would use its Jackson mapper to do it, so you'd get a response like:
[{"someProp":"someProp", "someListOfProps": ["prop1", "prop2"]}]
The same way, you can bind to some objects, but this time, using the #RequestBody annotation, where jackson would be used this time to pre-convert the json for you.
what you can do is
#RequestMapping("/someOtherRequestMapping")
public void doStuff(#RequestBody List<SomePojo> somePojos) {
//do stuff with the pojos
}
Try returning a list from the method:
#RequestMapping("/greetings")
public #ResponseBody List<Greeting> greetings(
#RequestParam(value="name", required=false, defaultValue="World") String name) {
return Arrays.asList(new Greeting(counter.incrementAndGet(),String.format(template, name)));
}