Create application structure
api
├── getHosts.sh
├── pom.xml
├── src
│ └── main
│ ├── java
│ │ └── com
│ │ └── cba
│ │ └── web
│ │ ├── host.java
│ │ └── hosts.java
│ └── webapp
│ ├── css
│ │ └── cba.css
│ ├── index.html
│ ├── META-INF
│ │ └── context.xml
│ └── WEB-INF
│ ├── cgi
│ └── web.xml
create a pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.cba.web</groupId>
<artifactId>api</artifactId>
<version>1</version>
<packaging>war</packaging>
<name>api</name>
<url>https://www.custom-built-apps.com</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<gson.version>2.9.0</gson.version>
<javax.servlet.version>3.1.0</javax.servlet.version>
</properties>
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>${javax.servlet.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>${gson.version}</version>
</dependency>
</dependencies>
<build>
<sourceDirectory>src/main/java/com/cba/web/</sourceDirectory>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>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>
Create class to hold the data for serialiazation/deserialiazation
// File : host.java
// Author : Boris Alexandrov
// Date : Tue Jul 5 21:09:02 EDT 2022
// Purpose : class to use for serialzation and deserializtion of JSON
///////////////////////////////////////////////////
package com.cba.web;
import java.util.*;
import java.io.*;
import java.lang.*;
public class host implements Serializable
{
String id;
String hostname;
String OS;
String IpAddress;
public host(String id, String hostname, String OS, String IpAddress)
{
this.id=id;
this.hostname=hostname;
this.OS=OS;
this.IpAddress=IpAddress;
}
public String getId() { return id; }
public String getOS() {return OS; }
public String getHostname() { return hostname;}
public String returnIpAddress() {return IpAddress;}
};
Create the servlet
// Author : Boris Alexandrov
// Date : Tue Jul 5 21:09:02 EDT 2022
// Purpose : Servlet for Tomcat webservices
///////////////////////////////////////////////////
package com.cba.web;
import java.sql.*;
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.lang.*;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
public class hosts extends HttpServlet
{
Connection conn = null;
public void init(ServletConfig config) throws ServletException
{
super.init(config);
}
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
String url = "jdbc:postgresql://192.168.2.30:5432/cbaadmin";
Properties props = new Properties();
props.setProperty("user","cbaadmin");
props.setProperty("password","pWdHeRe");
PrintWriter out = response.getWriter();
try
{
Connection conn = DriverManager.getConnection(url, props);
String strSQL="select h.id,h.hostname,o.name,h.ip_address from public.hosts h join public.os o on o.id=h.os_id";
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery(strSQL);
conn.close();
Vector<host> hs= new Vector<host>();
while(rs.next())
{
hs.add(new host(rs.getString(1),rs.getString(2),rs.getString(3),rs.getString(4)));
}
GsonBuilder builder = new GsonBuilder();
builder.setPrettyPrinting();
Gson gson = builder.create();
String hostsJsonString = gson.toJson(hs);
response.setContentType("application/json");
response.setCharacterEncoding("UTF-8");
out.print(hostsJsonString);
out.flush();
}
catch(SQLException e)
{
out.println(e.getMessage());
}
}
};
create 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>webservice api</display-name>
<servlet>
<servlet-name>hosts</servlet-name>
<servlet-class>com.cba.web.hosts</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet>
<servlet-name>cgi</servlet-name>
<servlet-class>org.apache.catalina.servlets.CGIServlet</servlet-class>
<init-param>
<param-name>cgiPathPrefix</param-name>
<param-value>WEB-INF/cgi</param-value>
</init-param>
<init-param>
<param-name>executable</param-name>
<param-value></param-value>
</init-param>
<init-param>
<param-name>passShellEnvironment</param-name>
<param-value>"true"</param-value>
</init-param>
<init-param>
<param-name>environment-variable-LD_LIBRARY_PATH</param-name>
<param-value>/usr/local/lib64:/usr/lib64:/usr/lib64/graphviz:/app/hadoop/lib/native:/usr/pgsql-10/lib</param-value>
</init-param>
<load-on-startup>5</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>cgi</servlet-name>
<url-pattern>/cgi-bin/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>hosts</servlet-name>
<url-pattern>/getHosts</url-pattern>
</servlet-mapping>
</web-app>
Build and deploy the application
from api directory(root)
mvn package
copy the war to /tmp
cp target/api-1.war /tmp/api.war
chmod 777 /tmp/api.war
deploy from tomcat application manager as tomcat user
Create a curl shell script
getHosts.sh
curl http://r02edge.custom-built-apps.com:1962/api/getHosts
Run the curl
[dataexplorer1@r02edge api]$ ./getHosts.sh
[
{
"id": "1",
"hostname": "r02edge",
"OS": "CentOS Linux release 7.8.2003 (Core)",
"IpAddress": "192.168.2.30"
},
{
"id": "2",
"hostname": "r01edge",
"OS": "CentOS Linux release 7.8.2003 (Core)",
"IpAddress": "192.168.2.22"
},
{
"id": "3",
"hostname": "datanode1",
"OS": "CentOS Linux release 7.8.2003 (Core)",
"IpAddress": "192.168.2.23"
},
{
"id": "4",
"hostname": "datanode2",
"OS": "CentOS Linux release 7.8.2003 (Core)",
"IpAddress": "192.168.2.24"
},
{
"id": "5",
"hostname": "datanode3",
"OS": "CentOS Linux release 7.8.2003 (Core)",
"IpAddress": "192.168.2.27"
},
{
"id": "6",
"hostname": "datanode4",
"OS": "CentOS Linux release 7.8.2003 (Core)",
"IpAddress": "192.168.2.28"
},
{
"id": "7",
"hostname": "datanode5",
"OS": "CentOS Linux release 7.8.2003 (Core)",
"IpAddress": "192.168.2.29"
},
{
"id": "8",
"hostname": "namenode1",
"OS": "CentOS Linux release 7.8.2003 (Core)",
"IpAddress": "192.168.2.25"
},
{
"id": "9",
"hostname": "namenode2",
"OS": "CentOS Linux release 7.8.2003 (Core)",
"IpAddress": "192.168.2.26"
}
]
