springboot-tracker

Created by Heather Dinh

TO RUN

1. Download repository and change directory into its location
2. Make sure you have your JAVA_HOME environment variable pointing to installation of Java and Maven is installed
3. In the Command Prompt, run $ mvn spring-boot:mvn
4. In a browser (like Chrome), type in localhost:8080 to display the web page!

Notes while building the Coronavirus tracker

• location: cd Desktop/csProjects/springboot-tracker/tracker
• start.spring.io will initialize a Spring Boot application for you
• probably better to use IntelliJ, but I'm just going to use Visual Studio
• not going to use a database here, using public data
• @ symbol is an annotation

HTTP protocol

• using a raw data csv file from GitHub repo that is updated daily
• need to convert the URL to a URI because the HTTP request can read that
• to make requests and responses by HTTP, include libraries from java

	import java.net.http.HttpClient;
	import java.net.http.HttpRequest;
	import java.net.http.HttpResponse;

• to take the body of the request and return it as a string HttpResponse<String> httpResponse = client.send(request, HttpResponse.BodyHandlers.ofString());
• this doesn't do anything right now because it is just a class, need to mark it as a Spring service stereotype by using @Service
• @PostConstruct tells application to execute this when the Service class is constructed

Parsing CSV file

• the pom.xml file (stands for Project Object Model) contains all config info used by Maven in the project
• need to add a dependency in the pom.xml so that we can read csv file
• need to pass in a reader to the csv iterator, convert string to StringReader object
• @Scheduled programs this function to run automatically on a regular basis
• need to specify a time, so use the "cron" expression which takes a string that has second, minute, day etc.
• by doing cron = "* * * * * *" this makes it run every second
• creating a list to store all the values, updates every hour

Controllers to access page from URL

• to render this in a UI format (basically go to a URL and have this data in the page)
• in order to get any page to show up when you access a URL, have to create a @Controller
• this HomeController should map to an html file that is located in the resources/templates folder
• when the GetMapping is called, it maps this to the root url
• home template is the html file
• this works because we are using the Thymeleaf dependency, so Spring Boot knows to do this
• have to use localhost:8080 port
• when you call controller and access the URL, put things on the Model
• pass in this Model object and this object will be accessible when rendering the HTML, can add attributes to it model.addAttribute("testName", "TEST");
• the s: is adding a String attribute to the model with value of the o:
• Thymeleaf is used to access this new attribute in the HTML file
• add the attribute to the model object, and access in the HTML by using th <p th:text="${testName}"></p>
• since using a service, can AutoWire into the Controller
• using a table, loop through all the stats in the locationStats ArrayList
• use th:each="location: ${locationStats}" to loop through, and the th:text from before to display attributes

Bootstrap Styling

• jumbotron used just to show more attention to all total cases
• total cases in general computed by adding all the total cases for each city allStats.stream().mapToInt(stat->stat.getLatestTotalCases()).sum();
• .stream() converts to a stream that is readable to console
• .mapToInt(stat->stat.getLatestTotalCases()) gets each latest case and turns it into an int
• .sum() adds all these cases together

Maven

• make sure that the environment variable named "JAVA_HOME" points to the installation of Java in Program Files
• can see where JAVA_HOME is by typing in $echo %JAVA_HOME% which works for env vars
• to run Maven, cd into the project (in this case it is in the tracker file) and type in command mvn spring-boot:run