Tomcat's immortality, learning notes of four mainstream middleware integrated by Alibaba P8 boss

import java.io.Writer;
import org.apache.catalina.Context;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.startup.Tomcat;

public class EmbeddedTomcatEx {

public static void main(String[] args) throws LifecycleException,
        InterruptedException, ServletException {

    Tomcat tomcat = new Tomcat();
    tomcat.setPort(8082);

    Context ctx = tomcat.addContext("/", new File(".").getAbsolutePath());

    Tomcat.addServlet(ctx, "Embedded", new HttpServlet() {
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) 
                throws ServletException, IOException {
            
            Writer w = resp.getWriter();
            w.write("Embedded Tomcat servlet.\n");
            w.flush();
            w.close();
        }
    });

    ctx.addServletMapping("/*", "Embedded");

    tomcat.start();
    tomcat.getServer().await();
}

}



Let's explain the function of the above code in sections below:

```java
Tomcat tomcat = new Tomcat();
tomcat.setPort(8082);

Tomcat starts on port 8082

Context ctx = tomcat.addContext("/", new File(".").getAbsolutePath());

Each application is mapped to a context. Using this addContext() method, we create a file that is not a JSP file and has no web XML file. We use the root context path and the current working directory of the document library.

Tomcat.addServlet(ctx, "Embedded", new HttpServlet() {
            @Override
            protected void service(HttpServletRequest req, HttpServletResponse resp) 
                    throws ServletException, IOException {
                
                Writer w = resp.getWriter();
                w.write("Embedded Tomcat servlet.\n");
                w.flush();
                w.close();
            }
        });

The addServlet() method adds a new servlet. The servlet uses a stream to respond to some text.

 ctx.addServletMapping("/*", "Embedded");

Servlet mapping controls how to access a servlet named Embedded. For our example, any URL will eventually call our servlet.

tomcat.start();
tomcat.getServer().await();

Finally, the Tomcat server starts.

The server is listening on port 8082, so type the following URL in your Web browser:

http://localhost:8082/

You can see the corresponding effect

summary

Basically, we use embedded Tomcat for the following purposes:

1) Rapid unit testing of Web components such as Java components

Instead of starting / stopping the Tomcat server and opening a Web browser for manual unit testing, you can use embedded Tomcat to automatically perform unit testing.

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