web_services.md

Controller and Model Class for Restful Web Services

REST API

An API is an application programming interface. It is a set of rules that allow programs to talk to each other. The developer creates the API on the server and allows the client to talk to it.

REST determines how the API looks like. It stands for "Representational State Transfer". It is a set of rules that developers follow when they create their API. One of these rules states that you should be able to get a piece of data when you link to a specific URL.

Each URL is called a request while the data sent back to you is called a response.

A request is made up of four things:

• The endpoint
• The method
• The headers
• The data (or body)

End-point structure

root-endpoint/?

The root-endpoint is the starting point of the API you're requesting from. The path determines the resource you're requesting for.

Controller Class

Controller receives HTTP requests from the Spring front controller and simply delegates them forward to a service layer.

Spring Boot annotations for handling different HTTP request types

• @RequestMapping — For handling any request type
• @GetMapping — GET request
• @PostMapping — POST request
• @PutMapping — PUT request
• @DeleteMapping — DELETE request

Example:

    @RestController
    @RequestMapping("/tenders")

    // public class EiCreateTenderType {
    public class EiCreateTenderType {
        private static final Logger logger = LogManager.getLogger(EiCreateTenderType.class);
        /*
        *   public actorID counterPartyID; public EiTenderType eiTender; public actorID 
        *   partyID; public refID requestID
        */

        @Autowired
        EiTenderType tenderDao;
        @RequestMapping("/")
        public String home() {
            return "Hello World";
        }

        // 1) To Save an tender
        // @RequestMapping(value = " /add", method = RequestMethod.POST)

        @PostMapping("/add")
        public EiTenderModel createTender(@Valid @RequestBody EiTenderModel bks) {
            logger.info(bks.toString());

            return tenderDao.save(bks);
        }
    }

Path variables are variables in the request URL and annotated with "@PathVariable". The request mappings are straightforward , the actual ** value ** of the mapping as well as the HTTP method, determine the target method for the request. @RequestBody will bind the parameters of the method to the body of the HTTP request, whereas @ResponseBody does the same for the response and return type.

Now, you can get all the tenders by going to the following URL in Postman:

http://localhost:8080/tenders/allTenders

You can screen a specific tender by going to the following URL and select GET.

http://localhost:8080/tenders/search/{id}

You can create a new tender by going to the following URL and select POST.

http://localhost:8080/tenders/add

Similarly, you can delete the tender by going to the assigned URL.

Model Class

Model Class in our case is for Tender which will have tenderID, emixBase, transactionID, status and date as its properties.

'@Table(name= "EiTender")' is used for creating a table with name EiTender in the MySQL database.

'@Column(name= "tenderID")' is used to create a column with a particular name 'tenderID' in the EiTender table in the database.

@JoinColumn annotation helps us specify the column we'll use for joining an entity association or element collection.

Finally, @NotNull annotation is used to apply Not Null Constraint on a column.

Getter and Setter methods are used to set and get the required information from Entity Model.

Example:

    @Entity
    @Table(name="EiTender")
    @EntityListeners(AuditingEntityListener.class)

    public class EiTenderModel {

        //private static final java.sql.Date CurrentDateTimeProvider = null;
        @Id
        @NotNull
        private long tenderID; // Primary key, we can have only one tender with the same ID
        @NotBlank
        private String emixBase;

        public String status = "Created";
        //GetCurrentDateTime.get;
        //private java.sql.Date Current_Time;
        //private static final DateFormat a = new SimpleDateFormat("yyyy/MM/dd");
        //@Temporal(TemporalType.DATE)
        //@DateTimeFormat(pattern="")
        private LocalDate Date = gdate();

        public LocalDate gdate() {
            LocalDate localDate = LocalDate.now();
            //LocalDate a = (DateTimeFormatter.ofPattern("yyyy/MM/dd").format(localDate));
            //Date date = new Date();
            //Date a;

            return (localDate);
        }
    }