Enhancing the Hello World Service with a Path Variable

The @PathVariable annotation is used to extract the value from the URI. It is most suitable for the RESTful web service where the URL contains some value. Spring MVC allows us to use multiple @PathVariable annotations in the same method. A path variable is a critical part of creating rest resources.

We will create another hello-world-bean request with a path parameter.

Step 1: Open the HelloWorldController.java file and add another helloWorldBean() service.

HelloWorldController.java

package com.javatpoint.server.main;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.context.annotation.Configuration;
@Configuration
//Controller
@RestController
public class HelloWorldController 
{
//using get method and hello-world URI
@GetMapping(path="/hello-world")
public String helloWorld()
{
return "Hello World";
}
@GetMapping(path="/hello-world-bean")
//method- which returns "Hello World"
public HelloWorldBean helloWorldBean()
{
return new HelloWorldBean("Hello World");//constructor of HelloWorldBean
}
//passing a path variable
@GetMapping(path="/hello-world/path-variable/{name}")
public HelloWorldBean helloWorldPathVariable(@PathVariable String name)
{
return new HelloWorldBean(String.format("Hello World, %s", name)); //%s replace the name
}
}

Whatever value we will pass to the path variable is picked up by the controller and returned to the response.

Step 2: Type the URL http://localhost:8080///hello-world/path-variable/javatpoint

Step 3: Run the HelloWorldController.java file. We get the following response on the browser.

Enhancing the Hello World Service with a Path Variable

Let's change the path variable once again: http://localhost:8080/hello-world/path-variable/Anubhav

We can see that whatever we are writing in the path variable is returned to the response.

Creating User Bean and User Service

In this section, we are going to create real resources users and the post. We will use a static array list to represent the data.

Step 1: Create a new package with the name com.javatpoint.server.main.user.

Step 2: Create a bean class (User) to store the user detail.

Right click on the package user -> New -> Class -> Provide Name -> Finish. Here, we have provided class name User.

Step 3: Define three private variables id, name, and dob.

Step 4: Generate Getters and Setters.

Right click on the file -> Source -> Generate Getters and Setters... ->Select All -> Generate.

Step 5: Generate toString.

Right click on the file -> Source -> Generate toString... ->Select All -> Generate.

Step 6: Generate Constructors.

Right click on the file -> Source -> Generate Constructor using Fields... -> Generate.

User.java

package com.javatpoint.server.main.user;
import java.util.Date;
public class User 
{
public User(Integer id, String name, Date dob) 
{
super();
this.id = id;
this.name = name;
this.dob = dob;
}
private Integer id;
private String name;
private Date dob;
public Integer getId() 
{
return id;
}
public void setId(Integer id) 
{
this.id = id;
}
public String getName() 
{
return name;
}
public void setName(String name) 
{
this.name = name;
}
public Date getDob() 
{
return dob;
}
public void setDob(Date dob) 
{
this.dob = dob;
}
@Override
public String toString() 
{
//return "User [id=" + id + ", name=" + name + ", dob=" + dob + "]";
return String.format("User [id=%s, name=%s, dob=%s]", id, name, dob);
}
}

Before moving to the next step first move HelloWorldBean.java and HelloWorldController.java in the package com.javatpoint.server.main.helloworld.

Step 7: Create a class with name UserDaoService in the package com.javatpoint.server.main.user.

UserDaoService.java

package com.javatpoint.server.main.user;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import org.springframework.stereotype.Component;
@Component
public class UserDaoService 
{
public static int usersCount=5;
//creating an instance of ArrayList
private static List<User> users=new ArrayList<>();
//static block 
static
{
//adding users to the list
users.add(new User(1, "John", new Date()));
users.add(new User(2, "Robert", new Date()));
users.add(new User(3, "Adam", new Date()));
users.add(new User(4, "Andrew", new Date()));
users.add(new User(5, "Jack", new Date()));
}
//method that retrieve all users from the list
public List<User> findAll()
{
return users;
}
//method that add the user in the list 
public User save(User user)
{
if(user.getId()==null)
{
//increments the user id
user.setId(++usersCount);
}
users.add(user);
return user;
}
//method that find a particular user from the list
public User findOne(int id)
{
for(User user:users)
{
if(user.getId()==id)
return user;
}
return null;
}
}

Implementing Get Methods for User Resource

Step 8: Now create a user controller class with name UserResource.

UserResource.java

package com.javatpoint.server.main.user;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class UserResource 
{
@Autowired
private UserDaoService service;
@GetMapping("/users")
public List<User> retriveAllUsers()
{
return service.findAll();
}
}

Step 9: Run the application and type the localhost:8080/users in the address bar of the browser. It returns the users list in JSON format.

If the date is displaying in the default timestamp format as:

"dob": "1500370250075"

We need to do setting for proper date format.

Open the application.properties file. Remove the debug configuration and add the following configuration:

The above statement telling the Jackson framework that when serializing don't treat the date as a timestamp.

Step 10: If we want to display a specific user detail on the browser, add the mapping "/user/{id}" and create a method retriveUser() in the UserResource.

UserResource.java

package com.javatpoint.server.main.user;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class UserResource 
{
@Autowired
private UserDaoService service;
@GetMapping("/users")
public List<User> retriveAllUsers()
{
return service.findAll();
}
//retrieves a specific user detail
@GetMapping("/users/{id}")
public User retriveUser(@PathVariable int id)
{
return service.findOne(id);
}
}

Step 11: Run the application and type localhost:8080/users/{id} in the browser. It returns the detail of the specific user id which we are passing in the path variable.

In the following image, we have retrieved the detail of the user having id 4.