code flow of pamarin api

PageData.java

package com.pamarin.api.model.page;

import com.pamarin.api.model.MetaProperty;
import com.pamarin.api.model.page.impl.PageContent;
import java.util.List;
import org.codehaus.jackson.map.annotate.JsonSerialize;

/**
 * @author jittagornp
 */
public class PageData<T extends PageContent> {

    @JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL)
    private String title;

    @JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL)
    private List<MetaProperty> metadata;

    @JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL)
    private T content;

    public static final PageData EMPTY = new PageData() {

        @Override
        public PageData setTitle(String title) {
            throw new UnsupportedOperationException("Unsupported setTitle method.");
        }

        @Override
        public PageData setMetadata(List metadata) {
            throw new UnsupportedOperationException("Unsupported setMetadata method.");
        }

        @Override
        public PageData setContent(PageContent content) {
            throw new UnsupportedOperationException("Unsupported setContent method.");
        }

    };

    public String getTitle() {
        return title;
    }

    public PageData<T> setTitle(String title) {
        this.title = title;
        return this;
    }

    public List<MetaProperty> getMetadata() {
        return metadata;
    }

    public PageData<T> setMetadata(List<MetaProperty> metadata) {
        this.metadata = metadata;
        return this;
    }

    public PageData<T> requireMedata(boolean requireMedata) {
        if (content == null) {
            throw new IllegalStateException("require page data content.");
        }

        title = content.getTitle();
        if (requireMedata) {
            content.buildPageMetadata();
            metadata = content.getMetadata();
        }

        return this;
    }
    
    public PageData<T> modify(){
        content.modify();
        return this;
    }

    public T getContent() {
        return content;
    }

    public PageData<T> setContent(T content) {
        this.content = content;
        return this;
    }
}

TripCtrl.java

package com.pamarin.rest.controller;

import com.pamarin.api.model.page.PageData;
import com.pamarin.rest.service.TripService;
import com.pamarin.rest.service.page.TripPageService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam; 
import org.springframework.web.bind.annotation.RestController;

/**
 * @author jittagornp
 */
@RestController
public class TripCtrl {

    @Autowired
    private TripPageService pageService;

    @RequestMapping(
            value = "/users/{username}/trips/{tripname}/pagedata",
            method = RequestMethod.GET
    )
    public PageData findPageDataByUsernameAndTripname(
            @PathVariable("username") String username,
            @PathVariable("tripname") String tripname,
            @RequestParam(
                    value = "metadata",
                    required = false,
                    defaultValue = "false"
            ) boolean requireMetadata
    ) {
        return pageService.findByUsernameAndTripname(
                username,
                tripname,
                requireMetadata
        );
    }
}

TripPageContent.java

package com.pamarin.api.model.page.impl;

import com.pamarin.api.domain.impl.TripPostPageResource;
import com.pamarin.api.model.entity.Trip;
import com.pamarin.api.page.metadata.MetaTag;
import com.pamarin.api.page.metadata.OpengraphProtocol;
import com.pamarin.api.page.PageTitle;
import com.pamarin.api.page.metadata.GooglePlusSnippet;
import com.pamarin.api.page.metadata.TwitterCardsMarkup;
import org.codehaus.jackson.annotate.JsonProperty;
import org.codehaus.jackson.map.annotate.JsonSerialize;
import static org.springframework.util.StringUtils.hasText;

/**
 * @author jittagornp
 */
public class TripPageContent extends PageContent {

    @JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL)
    private Trip trip;

    @JsonProperty("post_page")
    @JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL)
    private TripPostPageResource postPage;

    public Trip getTrip() {
        return trip;
    }

    public TripPageContent setTrip(Trip trip) {
        this.trip = trip;
        return this;
    }

    public TripPostPageResource getPostPage() {
        return postPage;
    }

    public TripPageContent setPostPage(TripPostPageResource postPage) {
        this.postPage = postPage;
        return this;
    }

    private String getDescription() {
        if (hasText(trip.getDescription())) {
            return trip.getDescription();
        }

        return trip.getName();
    }

    private void htmlMetadata() {
        addPageMetadata(MetaTag.require(
                "key",
                getDescription()
        ));
    }

    private void facebookMetadata() {
        OpengraphProtocol graph = OpengraphProtocol.require(
                getTitle(),
                "article",
                "image",
                trip.getLink().getHref()
        )
                .addLocale(trip.getUser().getLocale())
                .addSitename(PageTitle.defaults())
                .addArticleAuthor(trip.getUser().getName())
                .addArticlePublishedTime(trip.getCreateDate())
                .addArticleModifiedTime(trip.getUpdateDate());

        trip.getTags().stream().forEach((tag) -> {
            graph.addArticleTag(
                    tag.getLookup().getDescription()
            );
        });

        addPageMetadata(graph);
    }

    private void twitterMetadata() {
        addPageMetadata(TwitterCardsMarkup.require(
                TwitterCardsMarkup.CardTypes.SUMMARY_WITH_LARGE_IMAGE
                .getDescription(),
                getTitle(),
                getDescription()
        )
                .addUrl(trip.getLink().getHref())
                .addImage("image")
        );
    }

    public void googlePlusMetadata() {
        addPageMetadata(GooglePlusSnippet.require(
                trip.getName(),
                getDescription(),
                trip.getLink().getHref()
        )
                .addImage("image")
                .addDatePublished(trip.getCreateDate())
                .addAuthor(trip.getUser().getName())
        );
    }

    @Override
    public void buildPageMetadata() {
        htmlMetadata();
        facebookMetadata();
        twitterMetadata();
        googlePlusMetadata();
    }

    @Override
    public String buildTitle() {
        return PageTitle.evaluate(trip.getName());
    }

    @Override
    public void modify() {
        trip.makePublic();
    }

}

TripPageService.java

package com.pamarin.rest.service.page;

import com.pamarin.api.model.page.PageData;
import com.pamarin.api.model.page.impl.TripPageContent;

/**
 * @author jittagornp
 */
public interface TripPageService {

    PageData<TripPageContent> findByUsernameAndTripname(
            String username,
            String tripname,
            boolean requireMetadata
    );
}

TripPageServiceImpl.java

package com.pamarin.rest.service.page.impl;

import com.pamarin.api.domain.impl.TripPostPageResource;
import com.pamarin.api.model.entity.Trip;
import com.pamarin.api.model.entity.User;
import com.pamarin.api.model.page.PageData;
import com.pamarin.api.model.page.impl.TripPageContent;
import com.pamarin.rest.service.Transactional;
import com.pamarin.rest.service.TripPostService;
import com.pamarin.rest.service.TripService;
import com.pamarin.rest.service.UserService;
import com.pamarin.rest.service.page.TripPageService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.PageRequest;
import org.springframework.stereotype.Service;
import org.springframework.transaction.TransactionStatus;

/**
 * @author jittagornp
 */
@Service
public class TripPageServiceImpl extends Transactional implements TripPageService {

    @Autowired
    private UserService userService;

    @Autowired
    private TripService service;

    @Autowired
    private TripPostService postService;

    private TripPageContent content(String username, String tripname) {
        User user = userService.findByUsername(username);
        Trip trip = service.findByTripnameAndUser(
                tripname,
                user
        );

        return new TripPageContent()
                .setTrip(trip)
                .setPostPage(
                        new TripPostPageResource(
                                postService.findByTripId(
                                        trip.getId(),
                                        new PageRequest(0, 5)
                                )
                        )
                );
    }

    @Override
    public PageData<TripPageContent> findByUsernameAndTripname(
            String username,
            String tripname,
            boolean requireMetadata
    ) {
        return new PageData<TripPageContent>()
                .setContent(
                        getTransaction().execute((TransactionStatus status) -> {
                            try {
                                return content(username, tripname);
                            } catch (RuntimeException ex) {
                                status.setRollbackOnly();
                                throw ex;
                            }
                        })
                )
                .requireMedata(requireMetadata)
                .modify();
    }

}