CustomResponseEntity.java

package com.medkhelifi.api;

import com.medkhelifi.exceptions.enums.ApiErrNumber;
import com.medkhelifi.api.error.ApiError;
import com.medkhelifi.api.error.ApiValidationError;
import com.medkhelifi.api.error.sub.ApiSubError;
import com.medkhelifi.exceptions.ApiException;
import com.medkhelifi.api.success.ApiSuccess;
import com.medkhelifi.api.success.ApiSuccessType;
import com.medkhelifi.util.Util;
import lombok.Getter;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.List;
import java.util.Objects;

/**
 * Extension of {@link ResponseEntity} that use {@link Api} to represent the HTTP response.
 * CustomResponseEntity use builder design pattern ({@link CustomResponseEntityBuilder}) to construct the {@link Api} response.
 *
 * <code>
 * return new CustomResponseEntity.CustomResponseEntityBuilder(OK)
 * .data("Hello World")
 * .build();
 * </code>
 * <p>
 * The constructor is private, the only way to instantiate it, is to go through the static nested {@link CustomResponseEntityBuilder} class
 * </p>
 *
 * @param <T> the body type
 * @author medKhelifi
 * @since 0.1.0
 */
public class CustomResponseEntity<T extends Api> extends ResponseEntity<T> {

    /**
     * Instantiates a new Custom response entity through {@link CustomResponseEntityBuilder}.
     *
     * @param customResponseEntityBuilder the custom response entity builder
     */
    private CustomResponseEntity(CustomResponseEntityBuilder<T> customResponseEntityBuilder){
        super(customResponseEntityBuilder.getApi(), customResponseEntityBuilder.api.getHttpStatus());
    }


    /**
     * The Custom response entity builder.
     *
     * @param <U> the type parameter
     */
    public static class CustomResponseEntityBuilder<U extends Api>{

        @Getter
        private U api;

        /**
         * Instantiates a new Custom response entity builder.
         *
         * @param cls    the cls
         * @param status the status
         * @throws ApiException the api exception
         */
        public CustomResponseEntityBuilder(Class<U> cls, HttpStatus status) throws ApiException {
            try {
                this.api = cls.getDeclaredConstructor(HttpStatus.class).newInstance(status);
            } catch (NullPointerException | IllegalAccessException | InstantiationException | NoSuchMethodException | InvocationTargetException e) {
                throw new ApiException(ApiErrNumber.API_0001, e);
            }
        }


        /**
         * Debug message custom response entity builder.
         *
         * @param ex the ex
         * @return the custom response entity builder
         * @throws ApiException the api exception
         */
        public CustomResponseEntityBuilder<U> debugMessage(Throwable ex) throws ApiException {
            this.validateApi();
            try{
                ( (ApiError ) this.api).setDebugMessage(ex.getCause()!=null? ex.getCause().getMessage(): ex.getLocalizedMessage());
            }catch (Exception castEx){
                throw new ApiException(ApiErrNumber.API_0002, castEx);
            }
            return this;
        }

        /**
         * Message custom response entity builder.
         *
         * @param message the message
         * @return the custom response entity builder
         * @throws ApiException the api exception
         */
        public CustomResponseEntityBuilder<U> message(java.lang.String message) throws ApiException {
            this.validateApi();
            this.api.setMessage(message);
            return this;
        }

        /**
         * Err number custom response entity builder.
         *
         * @param apiErrNumber the Api error number
         * @return CustomResponseEntityBuilder custom response entity builder
         * @throws ApiException the api exception
         */
        public CustomResponseEntityBuilder<U> errNumber(String apiErrNumber) throws ApiException {
            this.validateApi();
            try{
                ( (ApiError) this.api).setErrNumber(apiErrNumber);
            }catch (ClassCastException castEx){
                throw new ApiException(ApiErrNumber.API_0002, castEx);
            }
            return this;
        }

        /**
         * Define the api success {@link ApiSuccessType}
         *
         * @param type the type of success response
         * @return the custom response entity builder
         * @throws ApiException the api exception
         */
        public CustomResponseEntityBuilder<U> type (ApiSuccessType type) throws ApiException {
            this.validateApi();
            try{
                ((ApiSuccess) this.api).setType(type);
            }catch (ClassCastException castEx){
                throw new ApiException(ApiErrNumber.API_0002, castEx);
            }
            return this;
        }

        /**
         * Data custom response entity builder.
         *
         * @param data the data
         * @return the custom response entity builder
         * @throws ApiException the api exception
         */
        public CustomResponseEntityBuilder<U> data (Object data) throws ApiException {
            this.validateApi();
            try{
                ((ApiSuccess) this.api).setData(data);
            }catch (ClassCastException castEx){
                throw new ApiException(ApiErrNumber.API_0002, castEx);
            }
            return this;
        }

        /**
         * Items list custom response entity builder
         *
         * @param items the list of items
         * @return the custom response entity builder
         * @throws ApiException the api exception
         */
        public CustomResponseEntityBuilder<U> items (List<Object> items) throws ApiException {
            this.validateApi();
            try{
                ((ApiSuccess) this.api).setItems(items);
            }catch (ClassCastException castEx){
                throw new ApiException(ApiErrNumber.API_0002, castEx);
            }
            return this;
        }

        /**
         * Add sub error custom response entity builder.
         *
         * @param apiSubError the api sub error
         * @return custom response entity builder
         * @throws ApiException the api exception
         */
        public CustomResponseEntityBuilder<U> addSubError(ApiSubError apiSubError) throws ApiException {
            this.validateApi();
            try{
                ((ApiValidationError) this.api).addValidationError(apiSubError);
            }catch (ClassCastException castEx){
                throw new ApiException(ApiErrNumber.API_0002, castEx);
            }
            return this;
        }

        /**
         * Sub error custom response entity builder.
         *
         * @param apiSubErrors the api sub errors
         * @return the custom response entity builder
         * @throws ApiException the api exception
         */
        public CustomResponseEntityBuilder<U> subError(List<ApiSubError> apiSubErrors) throws ApiException {
            this.validateApi();
            try{
                ((ApiValidationError) this.api).setSubErrors(apiSubErrors);
            }catch (ClassCastException castEx){
                throw new ApiException(ApiErrNumber.API_0002, castEx);
            }
            return this;
        }
        /**
         * check the {@link Api} instance if it's valid
         */
        private void validateApi() throws ApiException {
            if(this.api == null )
                throw new ApiException(ApiErrNumber.API_0003);

        }

        /**
         * Return the final constructed {@link CustomResponseEntity}
         *
         * @return CustomResponseEntity custom response entity
         */
        public CustomResponseEntity<U> build(){
            return new CustomResponseEntity<>(this);
        }

    }

    /**
     * Write the {@link HttpServletResponse} response by passing the CustomResponseEntity {@link Api}
     *
     * @param res The {@link HttpServletResponse }
     * @throws IOException Throw {@link IOException} if some problem occurred when {@link HttpServletResponse} writer.
     */
    public void responseWriter(HttpServletResponse res) throws IOException {
        res.setStatus(this.getStatusCode().value());
        res.setContentType("application/json");
        res.getWriter().write(Objects.requireNonNull(Util.convertObjectToJson((this.getBody()) )));
    }


}