springmvc4开发rest

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springmvc4开发rest
Spring MVC 4 RESTFul Web Services CRUD Example+RestTemplate

Created on:

August 11, 2015

| Last updated on:

March 12, 2017

websystiqueadmin

In this post we will write a CRUD Restful WebService using Spring MVC 4, and write a REST client with RestTemplate to consume those services. We will also test those services using external clients. Let’s get started.

Short & Quick introduction to REST

REST stands for Representational State Transfer.It’s an is an architectural style which can be used to design web services, that can be consumed from a variety of clients. The core idea is that, rather than using complex mechanisms such as CORBA, RPC or SOAP to connect between machines, simple HTTP is used to make calls among them.

In Rest based design, resources are being manipulated using a common set of verbs.
- To Create a resource : HTTP POST should be used
- To Retrieve a resource : HTTP GET should be used
- To Update a resource : HTTP PUT should be used
- To Delete a resource : HTTP DELETE should be used
That means, you as a REST service developer or Client, should comply to above criteria, in order to be REST complained.

Often Rest based Web services return JSON or XML as response, although it is not limited to these types only. Clients can specify (using HTTP Accept header) the resource type they are interested in, and server may return the resource , specifying Content-Type of the resource it is serving. This StackOverflow link is a must read to understand REST in detail.

Other interesting posts you may like
Rest Based Controller

Following is one possible Rest based controller, implementing REST API. I said possible, means Other’s may implement it in another way, still (or even more pure way) conforming to REST style.

This is what our REST API does:
- GET request to /api/user/ returns a list of users
- GET request to /api/user/1 returns the user with ID 1
- POST request to /api/user/ with a user object as JSON creates a new user
- PUT request to /api/user/3 with a user object as JSON updates the user with ID 3
- DELETE request to /api/user/4 deletes the user with ID 4
- DELETE request to /api/user/ deletes all the users
```
package com.websystique.springmvc.controller;import java.util.List;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.http.HttpHeaders;import org.springframework.http.HttpStatus;import org.springframework.http.MediaType;import org.springframework.http.ResponseEntity;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestBody;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.RestController;import org.springframework.web.util.UriComponentsBuilder;import com.websystique.springmvc.model.User;import com.websystique.springmvc.service.UserService;@RestControllerpublic class HelloWorldRestController {@AutowiredUserService userService;  //Service which will do all data retrieval/manipulation work//-------------------Retrieve All Users--------------------------------------------------------@RequestMapping(value = "/user/", method = RequestMethod.GET)public ResponseEntity<List<User>> listAllUsers() {List<User> users = userService.findAllUsers();if(users.isEmpty()){return new ResponseEntity<List<User>>(HttpStatus.NO_CONTENT);//You many decide to return HttpStatus.NOT_FOUND}return new ResponseEntity<List<User>>(users, HttpStatus.OK);}//-------------------Retrieve Single User--------------------------------------------------------@RequestMapping(value = "/user/{id}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)public ResponseEntity<User> getUser(@PathVariable("id") long id) {System.out.println("Fetching User with id " + id);User user = userService.findById(id);if (user == null) {System.out.println("User with id " + id + " not found");return new ResponseEntity<User>(HttpStatus.NOT_FOUND);}return new ResponseEntity<User>(user, HttpStatus.OK);}//-------------------Create a User--------------------------------------------------------@RequestMapping(value = "/user/", method = RequestMethod.POST)public ResponseEntity<Void> createUser(@RequestBody User user, UriComponentsBuilder ucBuilder) {System.out.println("Creating User " + user.getName());if (userService.isUserExist(user)) {System.out.println("A User with name " + user.getName() + " already exist");return new ResponseEntity<Void>(HttpStatus.CONFLICT);}userService.saveUser(user);HttpHeaders headers = new HttpHeaders();headers.setLocation(ucBuilder.path("/user/{id}").buildAndExpand(user.getId()).toUri());return new ResponseEntity<Void>(headers, HttpStatus.CREATED);}//------------------- Update a User --------------------------------------------------------@RequestMapping(value = "/user/{id}", method = RequestMethod.PUT)public ResponseEntity<User> updateUser(@PathVariable("id") long id, @RequestBody User user) {System.out.println("Updating User " + id);User currentUser = userService.findById(id);if (currentUser==null) {System.out.println("User with id " + id + " not found");return new ResponseEntity<User>(HttpStatus.NOT_FOUND);}currentUser.setName(user.getName());currentUser.setAge(user.getAge());currentUser.setSalary(user.getSalary());userService.updateUser(currentUser);return new ResponseEntity<User>(currentUser, HttpStatus.OK);}//------------------- Delete a User --------------------------------------------------------@RequestMapping(value = "/user/{id}", method = RequestMethod.DELETE)public ResponseEntity<User> deleteUser(@PathVariable("id") long id) {System.out.println("Fetching & Deleting User with id " + id);User user = userService.findById(id);if (user == null) {System.out.println("Unable to delete. User with id " + id + " not found");return new ResponseEntity<User>(HttpStatus.NOT_FOUND);}userService.deleteUserById(id);return new ResponseEntity<User>(HttpStatus.NO_CONTENT);}//------------------- Delete All Users --------------------------------------------------------@RequestMapping(value = "/user/", method = RequestMethod.DELETE)public ResponseEntity<User> deleteAllUsers() {System.out.println("Deleting All Users");userService.deleteAllUsers();return new ResponseEntity<User>(HttpStatus.NO_CONTENT);}}
```
Detailed Explanation :

@RestController : First of all, we are using Spring 4′s new @RestController annotation. This annotation eliminates the need of annotating each method with @ResponseBody. Under the hood, @RestController is itself annotated with @ResponseBody, and can be considered as combination of @Controller and @ResponseBody.

@RequestBody : If a method parameter is annotated with @RequestBody, Spring will bind the incoming HTTP request body(for the URL mentioned in @RequestMapping for that method) to that parameter. While doing that, Spring will [behind the scenes] use HTTP Message converters to convert the HTTP request body into domain object [deserialize request body to domain object], based on ACCEPT or Content-Type header present in request.

@ResponseBody : If a method is annotated with @ResponseBody, Spring will bind the return value to outgoing HTTP response body. While doing that, Spring will [behind the scenes] use HTTP Message converters to convert the return value to HTTP response body [serialize the object to response body], based on Content-Type present in request HTTP header. As already mentioned, in Spring 4, you may stop using this annotation.

ResponseEntity is a real deal. It represents the entire HTTP response. Good thing about it is that you can control anything that goes into it. You can specify status code, headers, and body. It comes with several constructors to carry the information you want to sent in HTTP Response.

@PathVariable This annotation indicates that a method parameter should be bound to a URI template variable [the one in '{}'].

Basically, @RestController , @RequestBody, ResponseEntity & @PathVariable are all you need to know to implement a REST API in Spring 4. Additionally, spring provides several support classes to help you implement something customized.

MediaType : With @RequestMapping annotation, you can additionally, specify the MediaType to be produced or consumed (using produces or consumesattributes) by that particular controller method, to further narrow down the mapping.

Deploy and Test this API, let’s dig deeper into how this thing works

At the at end of day, it’s just a plain controller class, part of a deploy-able application.[Complete downloadable application code is shown further down in post which you can deploy straight-away in your container]. I am going to deploy it, in order to see things live and discuss each operation in detail. Deployed Application is available at http://localhost:8080/Spring4MVCCRUDRestService.

To test this API, i will use an external client POSTMAN (An extension from CHROME). We will write our own client in just few minutes.

1. Retrieve all users

Open POSTMAN tool, select request type [GET for this usecase], specify the operation uri.

Notice that we did not specify any HTTP header here. Click on Send, you will receive list of all users.

Also notice the HTTP 200 response. Additionally check headers.

You might be wondering how the response is sent as JSON string, and the Content-Type header in response confirms that. Glad you asked. This is due to the fact that we have included Jackson library in our project.
```
<dependency>    <groupId>com.fasterxml.jackson.core</groupId>    <artifactId>jackson-databind</artifactId>    <version>2.5.3</version></dependency>
```
Since spring finds this library in class path, it invokes inbuilt MappingJackson2HttpMessageConverterconverter to convert the response (List of objects) into JSON.

Good thing about Spring inbuilt converters are that most of the time they just need certain library in classpath in order to perform conversion. Of course sometime we do need to adapt our API/application as well. For instance, if we want to serve XML as well, we should annotate User class with proper JAXB annoations.

2. Retrieve Single User

Specify a GET with /user/1 , click on send.

Now try to send a GET with invalid identifier, you should receive a HTTP 404.

3. Create a User

Select the method as POST, specify uri as /user/, specify body in POSTMAN body tab, select the type [application/json].

You might have noticed that POSTMAN automatically adds a header Content-Type.

Along with POST and PUT request, clients send the data to the server and they should specify the actual content type of the data being sent.

Remember : Accept header says about what type client can understand. Content-Type header says what type of data actually is of.

Send. You should see HTTP 200 response with no body (as API don’t send anything in body). But you should find a Location header specifying the location the newly created user can be found at.

You can now fetch the newly created user.

This way of implementation is common in REST. But no one stops you if you do want to send the content in Response body of a POST/PUT request. Will that still be REST complaint API? It’s a debatable point.

Anyway, Lets try to create the same user again.You should get HTTP Conflict response.

4. Update a User

Send a HTTP PUT request to update a user. Send along the new user details to be put in.

Notice that we have received response body this time. This is because the method implementation in controller is sending it. Again, one may decide not to send the updated details in response body, and just send the location header(as in create).

5. Delete a User

6. Delete All Users

7. Verify users after delete-all

Writing REST Client using RestTemplate

Postman tool we used above is a wonderful Client to test Rest API. But if you want to consume REST based web services from your application, you would need a REST client for your application. One of the most popular HTTP client is Apache HttpComponents HttpClient. But the details to access REST services using this are too low level.

Spring’s RestTemplate comes to Rescue. RestTemplate provides higher level methods that correspond to each of the six main HTTP methods that make invoking many RESTful services a one-liner and enforce REST best practices.

Below shown are HTTP methods and corresponding RestTemplate methods to handle that type of HTTP request.

HTTP Methods and corresponding RestTemplate methods:
- HTTP GET : getForObject, getForEntity
- HTTP PUT : put(String url, Object request, String…urlVariables)
- HTTP DELETE : delete
- HTTP POST : postForLocation(String url, Object request, String… urlVariables), postForObject(String url, Object request, ClassresponseType, String… uriVariables)
- HTTP HEAD : headForHeaders(String url, String… urlVariables)
- HTTP OPTIONS : optionsForAllow(String url, String… urlVariables)
- HTTP PATCH and others : exchange execute
Custom Rest client , consuming the REST services created earlier.
```
package com.websystique.springmvc;import java.net.URI;import java.util.LinkedHashMap;import java.util.List;import org.springframework.web.client.RestTemplate;import com.websystique.springmvc.model.User;public class SpringRestTestClient {public static final String REST_SERVICE_URI = "http://localhost:8080/Spring4MVCCRUDRestService";/* GET */@SuppressWarnings("unchecked")private static void listAllUsers(){System.out.println("Testing listAllUsers API-----------");RestTemplate restTemplate = new RestTemplate();List<LinkedHashMap<String, Object>> usersMap = restTemplate.getForObject(REST_SERVICE_URI+"/user/", List.class);if(usersMap!=null){for(LinkedHashMap<String, Object> map : usersMap){            System.out.println("User : id="+map.get("id")+", Name="+map.get("name")+", Age="+map.get("age")+", Salary="+map.get("salary"));;        }}else{System.out.println("No user exist----------");}}/* GET */private static void getUser(){System.out.println("Testing getUser API----------");RestTemplate restTemplate = new RestTemplate();        User user = restTemplate.getForObject(REST_SERVICE_URI+"/user/1", User.class);        System.out.println(user);}/* POST */    private static void createUser() {System.out.println("Testing create User API----------");    RestTemplate restTemplate = new RestTemplate();        User user = new User(0,"Sarah",51,134);        URI uri = restTemplate.postForLocation(REST_SERVICE_URI+"/user/", user, User.class);        System.out.println("Location : "+uri.toASCIIString());    }    /* PUT */    private static void updateUser() {System.out.println("Testing update User API----------");        RestTemplate restTemplate = new RestTemplate();        User user  = new User(1,"Tomy",33, 70000);        restTemplate.put(REST_SERVICE_URI+"/user/1", user);        System.out.println(user);    }    /* DELETE */    private static void deleteUser() {System.out.println("Testing delete User API----------");        RestTemplate restTemplate = new RestTemplate();        restTemplate.delete(REST_SERVICE_URI+"/user/3");    }    /* DELETE */    private static void deleteAllUsers() {System.out.println("Testing all delete Users API----------");        RestTemplate restTemplate = new RestTemplate();        restTemplate.delete(REST_SERVICE_URI+"/user/");    }    public static void main(String args[]){listAllUsers();getUser();createUser();listAllUsers();updateUser();listAllUsers();deleteUser();listAllUsers();deleteAllUsers();listAllUsers();    }}
```
Restart server(In our example, data on server side is fixed.). Run above program.

Output from above Client program
```
Testing listAllUsers API-----------User : id=1, Name=Sam, Age=30, Salary=70000.0User : id=2, Name=Tom, Age=40, Salary=50000.0User : id=3, Name=Jerome, Age=45, Salary=30000.0User : id=4, Name=Silvia, Age=50, Salary=40000.0Testing getUser API----------User [id=1, name=Sam, age=30, salary=70000.0]Testing create User API----------Location : http://localhost:8080/Spring4MVCCRUDRestService/user/5Testing listAllUsers API-----------User : id=1, Name=Sam, Age=30, Salary=70000.0User : id=2, Name=Tom, Age=40, Salary=50000.0User : id=3, Name=Jerome, Age=45, Salary=30000.0User : id=4, Name=Silvia, Age=50, Salary=40000.0User : id=5, Name=Sarah, Age=51, Salary=134.0Testing update User API----------User [id=1, name=Tomy, age=33, salary=70000.0]Testing listAllUsers API-----------User : id=1, Name=Tomy, Age=33, Salary=70000.0User : id=2, Name=Tom, Age=40, Salary=50000.0User : id=3, Name=Jerome, Age=45, Salary=30000.0User : id=4, Name=Silvia, Age=50, Salary=40000.0User : id=5, Name=Sarah, Age=51, Salary=134.0Testing delete User API----------Testing listAllUsers API-----------User : id=1, Name=Tomy, Age=33, Salary=70000.0User : id=2, Name=Tom, Age=40, Salary=50000.0User : id=4, Name=Silvia, Age=50, Salary=40000.0User : id=5, Name=Sarah, Age=51, Salary=134.0Testing all delete Users API----------Testing listAllUsers API-----------No user exist----------
```
Complete Example

Project Structure

Declare project dependencies
```
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">  <modelVersion>4.0.0</modelVersion>  <groupId>com.websystique.springmvc</groupId>  <artifactId>Spring4MVCCRUDRestService</artifactId>  <packaging>war</packaging>  <version>1.0.0</version>  <name>Spring4MVCCRUDRestService Maven Webapp</name>  <properties><springframework.version>4.2.0.RELEASE</springframework.version><jackson.version>2.5.3</jackson.version></properties><dependencies><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>${springframework.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-tx</artifactId><version>${springframework.version}</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId>    <artifactId>jackson-databind</artifactId>    <version>${jackson.version}</version></dependency><dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version></dependency></dependencies><build><pluginManagement><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><version>3.2</version><configuration><source>1.7</source><target>1.7</target></configuration></plugin><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-war-plugin</artifactId><version>2.4</version><configuration><warSourceDirectory>src/main/webapp</warSourceDirectory><warName>Spring4MVCCRUDRestService</warName><failOnMissingWebXml>false</failOnMissingWebXml></configuration></plugin></plugins></pluginManagement><finalName>Spring4MVCCRUDRestService</finalName></build></project>
```
User Service
```
package com.websystique.springmvc.service;import java.util.List;import com.websystique.springmvc.model.User;public interface UserService {User findById(long id);User findByName(String name);void saveUser(User user);void updateUser(User user);void deleteUserById(long id);List<User> findAllUsers(); void deleteAllUsers();public boolean isUserExist(User user);}
```
```
package com.websystique.springmvc.service;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.concurrent.atomic.AtomicLong;import org.springframework.stereotype.Service;import org.springframework.transaction.annotation.Transactional;import com.websystique.springmvc.model.User;@Service("userService")@Transactionalpublic class UserServiceImpl implements UserService{private static final AtomicLong counter = new AtomicLong();private static List<User> users;static{users= populateDummyUsers();}public List<User> findAllUsers() {return users;}public User findById(long id) {for(User user : users){if(user.getId() == id){return user;}}return null;}public User findByName(String name) {for(User user : users){if(user.getName().equalsIgnoreCase(name)){return user;}}return null;}public void saveUser(User user) {user.setId(counter.incrementAndGet());users.add(user);}public void updateUser(User user) {int index = users.indexOf(user);users.set(index, user);}public void deleteUserById(long id) {for (Iterator<User> iterator = users.iterator(); iterator.hasNext(); ) {    User user = iterator.next();    if (user.getId() == id) {        iterator.remove();    }}}public boolean isUserExist(User user) {return findByName(user.getName())!=null;}private static List<User> populateDummyUsers(){List<User> users = new ArrayList<User>();users.add(new User(counter.incrementAndGet(),"Sam",30, 70000));users.add(new User(counter.incrementAndGet(),"Tom",40, 50000));users.add(new User(counter.incrementAndGet(),"Jerome",45, 30000));users.add(new User(counter.incrementAndGet(),"Silvia",50, 40000));return users;}public void deleteAllUsers() {users.clear();}}
```
Model class
```
package com.websystique.springmvc.model;public class User {private long id;private String name;private int age;private double salary;public User(){id=0;}public User(long id, String name, int age, double salary){this.id = id;this.name = name;this.age = age;this.salary = salary;}public long getId() {return id;}public void setId(long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public double getSalary() {return salary;}public void setSalary(double salary) {this.salary = salary;}@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + (int) (id ^ (id >>> 32));return result;}@Overridepublic boolean equals(Object obj) {if (this == obj)return true;if (obj == null)return false;if (getClass() != obj.getClass())return false;User other = (User) obj;if (id != other.id)return false;return true;}@Overridepublic String toString() {return "User [id=" + id + ", name=" + name + ", age=" + age+ ", salary=" + salary + "]";}}
```
Configuration class
```
package com.websystique.springmvc.configuration;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.web.servlet.config.annotation.EnableWebMvc;@Configuration@EnableWebMvc@ComponentScan(basePackages = "com.websystique.springmvc")public class HelloWorldConfiguration {}
```
Initialization Class
```
package com.websystique.springmvc.configuration;import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;public class HelloWorldInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {     @Override    protected Class<?>[] getRootConfigClasses() {        return new Class[] { HelloWorldConfiguration.class };    }      @Override    protected Class<?>[] getServletConfigClasses() {        return null;    }      @Override    protected String[] getServletMappings() {        return new String[] { "/" };    } }
```
Adding CORS support to your REST API

While accessing the REST API, you might face issues concerning Same Origin Policy.

Errors like :

” No ‘Access-Control-Allow-Origin’ header is present on the requested resource. Origin‘http://127.0.0.1:8080′ is therefore not allowed access.” OR

” XMLHttpRequest cannot load http://abc.com/bla. Origin http://localhost:12345 is not allowed by Access-Control-Allow-Origin.” are common in such case.

Solution is Cross-Origin Resource Sharing. Basically, on server side, we can return additional CORS access control headers with response, which will eventually allow further inter-domain communication.

With Spring, we can write a simple filter which adds those CORS specific headers in each response.
```
package com.websystique.springmvc.configuration;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletResponse;public class CORSFilter implements Filter {public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {System.out.println("Filtering on...........................................................");HttpServletResponse response = (HttpServletResponse) res;response.setHeader("Access-Control-Allow-Origin", "*");response.setHeader("Access-Control-Allow-Methods", "POST, GET, PUT, OPTIONS, DELETE");response.setHeader("Access-Control-Max-Age", "3600");response.setHeader("Access-Control-Allow-Headers", "x-requested-with");chain.doFilter(req, res);}public void init(FilterConfig filterConfig) {}public void destroy() {}}
```
Then we can simply configure it in our Spring configuration like shown below:
```
package com.websystique.springmvc.configuration;import javax.servlet.Filter;import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;public class HelloWorldInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {     @Override    protected Class<?>[] getRootConfigClasses() {        return new Class[] { HelloWorldConfiguration.class };    }      @Override    protected Class<?>[] getServletConfigClasses() {        return null;    }      @Override    protected String[] getServletMappings() {        return new String[] { "/" };    }        @Override    protected Filter[] getServletFilters() {    Filter [] singleton = { new CORSFilter()};    return singleton;    } }
```
That’s it. With these two additional steps, clients will be able to communicate with your REST API without worrying about Cross domain issues.

Download Source Code

Download Now!

With CORS support:

Download Now!

References
- Spring framework
websystiqueadmin

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websystique

Hi, They both will work, but you should look at them from REST client point of view. Do you want to return the deleted user [then use ResponseEntity ] or you simply want to delete the user and return the HTTP success. I’m using the second approach assuming that client is not interested in knowing the deleted user anymore.You may choose other approaches.
websystique

Hello Ganesh, please have a look at Setup Tomcat+Eclipse, should fix your issue.

Siphenkosi Filtane

Hi Websystique

I am a big fan of tutorials, I love them.

However, I still have this same issue as I did not have to configure Tomcat since all other tuts are running fine.

https://uploads.disquscdn.com/images/90dfabaaeb52ca91380d7859f95c1bb23951439f73ceece587228a25cc966fc8.png

Siphenkosi Filtane

Okay I have figured it out, thanks.
websystique

Hi Deepak, Probably your local tomcat setup is having some issue. Please have a look at Setup Tomcat with Eclipse, should be fine.

MadanMohan Sinha

Still facing same issue 404.
websystique

Hi Mahesh, Please make sure that ‘jackson-databind’ dependency is included in your pom.xml.
websystique

Hi Andrey, Not sure how i missed your message, but here i am.

About your first question : Post relates to HTTP POST while Put to HTTP Put. In both, you send content as request body, but POST is [conceptually] used for ‘Create’ while Put is used for ‘update’.For Post, as object is not created yet, we don’t have id yet. For Put, we do have the object id [and it CAN be sent as part of request body], the object id is the key to look for original object which will be updated with new content.

For the second question: Server can send the requested resource in different formats depending on the client request ['Accept' header]. ‘Content-Type’ Header in HTTP request is special and is essential in a PUT or POST request. With PUT/POST, client is actually sending a bunch of data to the server as part of the request, and the Content-Type header tells the server what the data actually is (and thus determines how the server will parse it).Without Content-Type header, server have no means of specifying what is the type of data in request [Unless server itself tries to figure it out but it is not mandatory on server part]. Hope it clarifies your doubt.
websystique

Hi Nilesh, did you try if your local seutp [Intellij+JBoss] works for any other project. It seems to me a configuration issue in your setup.
Stone Patterson

what would i need to change . add . delete. update, etc. if anything at all in order to have this function in IntelliJ?

websystique

I don’t think you need any change.Did you get any error while running on IntelliJ?

Stone Patterson

Couldn’t get this /import com.websystique.springmvc.model.User;// to resolve symbol error .

websystique

Did you refresh and then build your project in intellij?

Stone Patterson

yes I did. any other suggestions

Stone Patterson

yes. I did a refresh. Still no luck.

websystique

Hi Stone, I just imported it into IntelliJ and no issue. Are you sure you have imported it correctly? Did you try to mark src/main/java directory as ‘sources root’? BTW, do you have any other projects successfully setup on your IDE?
websystique

Hey ismael, only saying that i get error is not so helpful.Could you please past complete exception so that we know where it was thrown?
websystique

Hi, I would recommend to start with Create a Maven Web Project with Eclipse, build and deploy it. For any deployment related issues you may face, post Setup Tomcat with Eclipse will help you. Once your basic app is working fine,i would recommend Spring MVC+Hibernate Crud App. Then you may want to look at Spring MVC+Hibernate Many-To-Many-Crud App.If AngularJS is your taste, Spring MVC CRUD with AngularJS would be interesting.And for REST, you are already looking that in this post. Enjoy the learning.

Gyver

Thank you very much sir for your advice! gonna look onto that and i just hope I’ll be able to learn from it….
websystique

Hi,it seems that you are asking the response of specific type [e.g. using Accept header in request] which is not supported by default. Please check your accept header. You can see in above examples that JSON is supported [since jackson-databind is in classpath]. Please have a look at this post to learn about the converters.

You may want to explicitly send the expected type using Headers. For instance, listAllUsers() can be re-written like following:

private static void listAllUsers(){

System.out.println(“Testing listAllUsers API———–”);

RestTemplate restTemplate = new RestTemplate();

HttpHeaders headers = new HttpHeaders();

headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));

HttpEntity request = new HttpEntity(headers);

ResponseEntity response = restTemplate.exchange(REST_SERVICE_URI+”/user/”, HttpMethod.GET, request, List.class);

List<LinkedHashMap> usersMap = (List<LinkedHashMap>)response.getBody();

if(usersMap!=null){

for(LinkedHashMap map : usersMap){

System.out.println(“User : id=”+map.get(“id”)+”, Name=”+map.get(“name”)+”, Age=”+map.get(“age”)+”, Salary=”+map.get(“salary”));;

}

}else{

System.out.println(“No user exist———-”);

}

}

Naina R

thnks for the answer…but my exception is still the same….i have edited the code…
websystique

Hi Chriso, It could be related to your environment setup. Have a look at Setup tomcat+Eclipse. Although that post is for tomcat, you can follow the similar procedure to setup your server with Eclipse.
websystique

Hi SG, you can implement everything in REST way. Even in this example post, the createUser method is written in a REST way, returning ResponseEntity with actual HTTP status code. We should implement our logic in a consistent way. Let me know if i misunderstood your question.

SG

Sorry If my question was not clear. I am talking about the initial view page to input data for the CreateUser method. Say for example user.jsp is the initial page, which is holding form input element to enter user information which in turns call the CreateUser REST api. In below code I am using a normal Spring Controller instead of REST. I believe below approach is a correct.

@Controller // Using a non REST Controller.

@RequestMapping(“/registerUser”)

public class HomeController {

@RequestMapping(method=RequestMethod.GET)

public String HomePage(Model model){

return “user”;

}

}
websystique

Hi hzms,

Spring provides different ways to implement applications. In case your application is build with REST architecture in mind, you take advantage of Spring REST support to implement your application. If not, you go for traditional Spring MVC controllers, returning views [instead of data & HTTP status codes].
websystique

Hi Ashish, i don’t have knowledge of mybatis yet, sorry, probably something for future.
websystique

Hi Maun, in that post, we are using Spring Security with CSRF enabled. Make sure that in your page, the expressions are evaluated [set in JSP].
websystique

Hi Sonia, this example does not required any authentication anywhere. Could it be that you are mixing it with requests for other posts [Spring Security]?
websystique

Hi Hendi, Sorry i missed it. For web pages in a Spring MVC based application, normally if we get the response from server as plain JSON, our preference [in 2016] should be using AngularJS [within jsp as shown SpringMVC+AngularJS Example or without jsp but with a template[Velocity/Freemarker] as shown Spring 4 MVC+AngularJS Routing Example using UI-Router]. But if for any reason you are stuck with plain JSP[no angularJS], you should consider using JQuery with JSP to get the response from server [using $.ajax()] and display in appropriate element [node] within your page.
websystique

Hi,

Functionally, AbstractAnnotationConfigDispatcherServletInitializer provides a way to handle the configuration you would normally specify in traditional web.xml: register a DispatcherServlet. It provides hooks to register classes & filters with global ContextLoaderListener as well as with DispatcherServlet. More detailed description can be found at Spring Docs.
websystique

As i am using Eclipse, i would suspect the tomcat configuration. Did you already go through each step from post Setup Tomcat with Eclipse?
websystique

Hi Sof, Is your tomcat deployment listening on 8282 or 8080?
websystique

Thanks for the comments Abhijit.
Ashmin Pathak

Thanks..

Schmit

http://localhost:8077/Spring4MVCCRUDRestService/user/it is working fine. we need to use user/

i downloaded tomcat 8.0 and builded it using maven 3.0 and pasted the war file in the webapps folder and clicked on start.bat. And as given in the postmaster i given extra / it worked fine for me
websystique

Hi Rupali,

Probably your local tomcat+Eclipse setup is not correct. Please have a look at Setting Tomcat with Eclipse, should be helpful.

Rupali Solaskar

its done!!!!!!

Thank you.!!!!!!!!!!!!

Yes you were correct there was problem in my setting of tomcat with Eclipse.

Great Work. its very helpful.
websystique

Hi, I don’t have a netbeans setup, but the problem itself seems similar to eclipse+tomcat when the tomcat is not configured properly with your IDE. To get an idea, you may want to refer to Setting Tomcat with Eclipse, and check if your IDE missing some specific configuration.
Antonio D.A. (adoalonso)

You should add the dependency to com.fasterxml.jackson.dataformat::jackson-dataformat-xml

com.fasterxml.jackson.dataformat

jackson-dataformat-xml

${jackson.version}
websystique

Hi, Your Tomcat setup seems not correct. Please follow Setup Tomcat With Eclipse, should be fine. Let me know if you still face issues.
websystique

Hi, Glad you found it useful.
websystique

Hi Balakrishna,

On your question to RestController capabilities, it DOES SUPPORTS multiple formats. But to handle different formats , it needs help of HttpMessageConverters. They are automatically registered based on the presence of specific libraries in classpath. This Post contains more detail on this topic.

Coming back to your issue, application/json should have been handled by default if you have jackson-databind library in classpath (as included in this tutorial). If it is, and you are not using any custom datatype which can not be directly converted to JSON, then most probably the issue is not on server but in sending the request.

Are you using jquery ajax to send the form-submission post request, then make sure you are setting the dataType & ContentType correctly.this link can be handy.

It always help to open Developer tool in your browser to see what’s going on wire, and if the Content-Type header is present with appropriate type. Let me know if you remain blocked, then we will dig in deeper together.

Balakrishna Pedada

Thank you for your reply, Yes I am sending jquery ajax request. I am able to get response only if I send my content type as JSON and form data as JSON data.

But If I am using “application/x-www-form-urlencoded” with form data I am getting a 415 error. Please find the below screenshots and My rest controller. Also I have included jackson databind in the classpath.

websystique

Hi, You did not mention anything about application/x-www-form-urlencoded before. Anyway, this post contains the info you are looking for. Basically you need to register Spring’s FormHttpMessageConverterto handle the type you mentioned.There is an example give in the post.
websystique

Hi Vikas,

Just download the zip and perform mvn clean install. you will get the war.
websystique

Hey Vikas,

This is because we are using Servlet 3.x based configurations.Everything we need is already there in HelloWorldInitializer.

Vikash Kumar

ok
websystique

Hi Maxim,

Sorry for late reply. What you need is a custom Date Serializer which can be found at this post. You can learn more about custom serailization at Gson Custom Serialization Example.
websystique

Hi,

Are you deploying on Weblogic externally or using it from within Eclipse? You might want to go through Setting Tomcat with Eclipse. Although the post is for setting up Tomcat, similar setup should be applicable for other servers/containers. Let me know if the outcome.

nmpg

I’m using Netbeans, and deploying to external Weblogic server (but through Netbeans IDE..). It works just fine with others projects (some from here actually), but for some reason does not work with this one.

By the way, I just tried http://websystique.com/springmvc/spring-mvc-4-angularjs-example/ and whenever accessing http://localhost:7001/Spring4MVCAngularJSExample/I get Error 403 –Forbidden..

I’m not even sure how I can debug this.. Any thoughts on what I may doing wrong?

Stone Patterson

what would i need to change . add . delete. update, etc. if anything at all in order to have this function in IntelliJ?
websystique

Hey Badr,

Seems you are missing Spring form taglib(spring-form.tld). Which version of Spring are you using? Do you have spring-webmvc dependency in your pom.xml, as in this post? Did you declare the form taglib in your JSP like shown below?
websystique

Hi Guilherme,

Yes it converts it to JSON. This is due to presence of jackson-databind in classpath. Eventually spring uses inbuilt MappingJackson2HttpMessageConverter to convert to/from json.

Look at this post to understand the conversion and other possible types.
websystique

Glad you liked it.
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