cbaWorkflow : Generating Tomcat servlets using maven and deploying them

Maven project structure schematics
Creating maven project structure for tomcat war creation
Deploying the war into tomcat
Testing the application run
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Maven project structure schematics

Creating maven project structure for tomcat war creation

Create a directory structure for the the application,the name will be secondapp.

mkdir secondapp

mkdir -p src/main/webapp/WEB-INF

mkdir -p src/main/java/com/cba/web

vi pom.xml

<groupId>com.cba.web</groupId>
<artifactId>secondapp</artifactId>
<version>1</version>
<packaging>war</packaging>

<name>secondapp</name>
<url>https://www.custom-built-apps.com</url>

<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.0</version>
<scope>provided</scope>
</dependency>
</dependencies>

<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>3.2.3</version>
<configuration>
<warSourceDirectory>src/main/webapp</warSourceDirectory>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>

vi src/main/webapp/WEB-INF/web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
version="3.1">

<display-name>connection to PostgreSQL</display-name>

<servlet>
<servlet-name>secondapp</servlet-name>
<servlet-class>com.cba.web.secondapp</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>secondapp</servlet-name>
<url-pattern>/secondapp</url-pattern>
</servlet-mapping>

</web-app>

vi src/main/java/com/cba/web/secondapp.java

// File : secondapp.java
// Author : Boris Alexandrov
// Date : Sun May 3 22:26:44 EDT 2020
// Purpose : Servlet for Tomcat
///////////////////////////////////////

package com.cba.web;
import java.sql.*;
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.lang.*;

public class secondapp extends HttpServlet
{

public void init(ServletConfig config) throws ServletException
{
super.init(config);
}

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{

String url = "jdbc:postgresql://192.168.2.23:5432/dataexplorerdb2";
Properties props = new Properties();
props.setProperty("user","dataexplorer2");
props.setProperty("password","SomePassWord");
PrintWriter out = response.getWriter();
out.println("<HTML>");
out.println("<HEAD>");
out.println("<TITLE>PostgresSQL testing</TITLE>");
out.println("<link rel=stylesheet type=text/css href=css/cba.css>");
out.println("</HEAD>");
out.println("<BODY>");
out.println("<H1>Product sales by the month</H1>");
// out.println("<H1>Establishing connection ...</H1>");
try
{
Connection conn = DriverManager.getConnection(url, props);
// out.println("<H1>Connected ..</H1>");
String strSQL="select * from product_sales_monthly";
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery(strSQL);
out.println("<TABLE>");
out.println("<TR><TH>Product</TH><TH>Month</TH><TH>Year</TH><TH>Amount,CAD</TH></TR>");
while(rs.next())
{

out.println("<TR>");
out.println("<TD>"+rs.getString("product")+"</TD>");
out.println("<TD>"+rs.getString("month")+"</TD>");
out.println("<TD>"+rs.getString(3)+"</TD>");
out.println("<TD>"+rs.getDouble(4)+"</TD>");
out.println("</TR>");
}
out.println("</TABLE>");
conn.close();
out.println("</BODY>");
out.println("</HTML>");

}
catch(SQLException e)
{
out.println(e.getMessage());
}

}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
doGet(request,response);
}

};

Build the application:

mvn package

......

[INFO] Building war: /home/dataexplorer1/projects/java/secondapp/target/secondapp-1.war