BlogPostDAO.java

package course;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.List;

import org.bson.Document;
import org.bson.conversions.Bson;

import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.Filters;
import com.mongodb.client.model.Sorts;
import com.mongodb.client.model.UpdateOptions;

public class BlogPostDAO {
    MongoCollection<Document> postsCollection;

    public BlogPostDAO(final MongoDatabase blogDatabase) {
        postsCollection = blogDatabase.getCollection("posts");
    }

    // Return a single post corresponding to a permalink
    public Document findByPermalink(String permalink) {

        // XXX HW 3.2,  Work Here
        Document post = postsCollection.find(Filters.eq("permalink", permalink)).first();

        return post;
    }

    // Return a list of posts in descending order. Limit determines
    // how many posts are returned.
    public List<Document> findByDateDescending(int limit) {

        // XXX HW 3.2,  Work Here
        // Return a list of DBObjects, each one a post from the posts collection
        List<Document> posts = postsCollection.find()//
                .sort(Sorts.descending("date"))//
                .limit(limit)//
                .into(new ArrayList<Document>());

        return posts;
    }


    public String addPost(String title, String body, List tags, String username) {

        System.out.println("inserting blog entry " + title + " " + body);

        String permalink = title.replaceAll("\\s", "_"); // whitespace becomes _
        permalink = permalink.replaceAll("\\W", ""); // get rid of non alphanumeric
        permalink = permalink.toLowerCase();


        // XXX HW 3.2, Work Here
        // Remember that a valid post has the following keys:
        // author, body, permalink, tags, comments, date
        //
        // A few hints:
        // - Don't forget to create an empty list of comments
        // - for the value of the date key, today's datetime is fine.
        // - tags are already in list form that implements suitable interface.
        // - we created the permalink for you above.

        // Build the post object and insert it
        Document post = new Document();
        post.append("title", title)//
                .append("author", username)//
                .append("body", body)//
                .append("permalink", permalink)//
                .append("tags", tags)//
                .append("comments", Collections.<Document> emptyList())//
                .append("date", new Date());

        postsCollection.insertOne(post);

        return permalink;
    }




    // White space to protect the innocent








    // Append a comment to a blog post
    public void addPostComment(final String name, final String email, final String body,
                               final String permalink) {

        // XXX HW 3.3, Work Here
        // Hints:
        // - email is optional and may come in NULL. Check for that.
        // - best solution uses an update command to the database and a suitable
        //   operator to append the comment on to any existing list of comments
        
        Document comment = new Document().append("author", name).append("body", body);
        if (email != null) {
            comment.append("email", email);
        }
        
        Bson update = new Document("$push", new Document("comments", comment));
        postsCollection.updateOne(Filters.eq("permalink", permalink), update, new UpdateOptions().upsert(true));

    }
}