CoderUCI is a an MIT-licensed open source project. It is a question and answer site designed for programmers discussions. In the website, users can post questions, generate tags, edit with markdown, make comments, search questions and receive notifications.
- Keywords: Java, Spring Boot, Maven, MyBatis, MySQL, Flyway
- ALpha version: https://www.coderuci.com
When visiting the home page, you can have an overview of proposed questions by the users. Every media thumbnails are consists of the questions information: proposer, question content, views, etc. Every question is classified by a tag that shows in the light-blue badge so that you can have a fast and intuitive understanding of the question. Your may also notice the trend of popular topics on the right side.
This site currently only supports login as a github user. Simply click the signin button on the top-right corner, it will authorize you and redirect you back to the index page. After signing in, you will be able to publish or reply or comment questions.
After clicking a specific question, you will be forward to the question detail page, where you can view it in the rendered markdown form. You can rank the answers by date/likes. Of course, you can answer the questions. The site also supports secondary comments, where you can have furthur discussions.
Clicking the Publish Button, you will be able to publish your questions. The editor is embedded with a markdown editor, so feel free to add codes!
If you wish to delete/edit your questions, simply click the buttons around the title. But of course, you will only be able to do the operations to your own articles.
If you don't want to search specific questions, you can click tags on the right of the index page, or search in the nav bar.
This site supports notification functions. If someone replied to your questions/comments, you will be notified. Unread notifications will be marked with a yellow badge indicating its status. In addition, you can view all the questions you have published in the 'My Questions' tab.
MyBatis framework provides friendly interaction between user and database operations. A simple usage of mybatis is to add @Mapperannotations to a mapper class that contacts with the database tables, then a person should add SQL sentences to retrieve expected sentences. However, every time if we modifies the database, or modified our methods that handling data, we need to modify the SQL sentences as well. With the assistance of mybatis generator, we can let the mybatis generate mapper according to the database automatically, and provides an encapsulated api for us to handle database operations without using SQL sentences. This is crucial to a project that needs long term maintainence.
Flyway is an open-source database-migration tool. Before we make modifications to the databases, we can write the commands to a flyway file so that all the scripts will be tracked and preserved like GIT. This will hugely simplify the difficulty of deployment for users other than the author
This is a trivial but important function in the question page. We may want to rank the answers according to the likes count/date published. However, this GET/POST request asking the database to change the orders of results may triggers a refresh of the whole webpage. To prevent that, a partial refresh function is implemented in the QuesitonController, so that only the expected results will be refreshed.
When users visit our website, exceptions may happens due to: page not exist, access not allowed, or server errors. The website is implemented with customized exception handlers that will indicate specific reasons to the users if a page cannot be visited.
In order to pass the cookie of a signed in user, a session interceptor is embedded in the project so that the status will be kept until the user logs out or cookies expires.
In order to rank the popular tags, we need to make statistics of questions based on their tags, views, likes and comments. However, if this ranking procedure is processed every time a user visits the site, it is very inefficient, because the server will execute commands in the form : sql select tag from question order by popular desc. If we want to explain the 'popular' index further, we have to spend more time handling this operation. Using a task scheduler will help us a lot. We will schedule a check of current popular index every N minutes, then update the results. This will saves us much time if the influx is high.
After clone the project, simply do the following command:
sudo apt install maven
mvn clean compile package
You will see a BUILD SUCCESS reminder if it succeeds. You can then start the project:
mvn spring-boot:run
If you encounter problems in any form, please move on to the following manual installation.
- a. Install MySQL on the server and create a user:
sudo apt update
sudo apt install mysql-server
> sudo mysql
> CREATE USER 'your_user_name'@'%' IDENTIFIED BY 'your_password';
- b. create and run a bash file that execute all db scripts (db.migration/):
for sql_file in `ls /path/to/directory`; do mysql -uUSER -pPASSWORD DATABASE < $sql_file ; done
Please verify in the commandline that you can access the database tables with your defined user.
- c. Modify
application.properties
github.client.id=your_github_app_id
github.client.secret=your_github_app_secret
github.redirect.uri=http://your_ip_or_localhost/callback
spring.datasource.url=jdbc:mysql://your_ip_or_localhost:3306/db_test?serverTimezone=GMT%2B8
spring.datasource.username=your_database_username
spring.datasource.password=your_database_password
- d. Try
mvn spring-boot:runIf no errors, congrats! Otherwise you can comment all the lines in the application.properties regarding the database, and check again. If it works, it means the database authentication failed. Possible reason includes the following :
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174) ~[mysql-connector-java-8.0.18.jar:8.0.18]
To handle this problem, modify the file:
/etc/mysql/mysql.conf.d/mysqld.cnf
. . .
lc-messages-dir = /usr/share/mysql
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address = 127.0.0.1
. . .
Change the bind-address to 0.0.0.0 so that the database can be visited by ip other than localhost. If question still exists, I suggest visiting https://stackoverflow.com/questions/6865538/solving-a-communications-link-failure-with-jdbc-and-mysql, where I get my solution.
mvn spring-boot:run
or:
nohup mvn spring-boot:run &
if you want to keep it running even if you close the terminal
If you wish to make changes to the database, please do the following every time you make changes and never make direct changes to the database.
Write your dbscripts and save as V?__Modify_table.sql, '?' is positive numbers following existing sequences. Then run the following scripts in the termainl:
flyway:migrate
Add the following block to the file generatorConfig.xml
<table tableName="your_table_name" domainObjectName="Model_name"></table>
Then, run the following command in the terminal:
mvn -Dmybatis.generator.overwrite=true mybatis-generator:generate
- Backstage/Admin page. Current operations handling database information can only be finished via terminal. It is in urgent need of a backstage system.
- Index Page: Choices for ranking by dates/likes/7days popular/30 days popular
- Markdown Editor: Support upload image
- Signup: Support user sign up within this site; add more support for platform like goole, linkedin, etc.
- Statistics & Analytics: Provide intuitive results for the site's information. I plan to use Google Analytics.
- Notifications from site manager: Alert and warn inappropriate behavior via notifications.
- Discussion Room: Able to hold a live discussion.
MIT License © Zhenhan Li. University of California, Irvine.