I tried running a DB access application on IKS + Db2 on IBM Cloud (6. Preparation of DB access application (java))
Introduction
This is the 6th installment of "IKS + Db2 on IBM Cloud to run the DB access app". Here, we will describe the preparation of the sample application.
The details of the implementation are as follows.
--Overview of compilation environment --Source preparation --War file output
I'm not an application developer myself, so a better way I think there are higher quality codes etc., but in this article the main purpose is to move it, Please note that quality, security, error handling, etc. are not considered. I personally don't like the hard coded table names, but don't worry.
Preparing the compilation environment
To compile from Java application source, you need an IDE (Integrated development Environment) that includes the JDK. (Strictly speaking, you can compile with just the JDK ...)
Use Eclipse for the IDE. (There is no deep meaning. Anything is fine) I'm Eclipse, but I'm a beginner, so I use Pleiades All in One Package. It seems that it can support Java EE all in one. The person who made it will have a headache. ..
Download the file for Windows from Pleiades All in One Package. (This time, we are using Eclipse 2020 in the figure below.)
At the link, download from Java Full Edition.
After downloading, unzip the zip file. (If the path is long, an error may occur, so place and expand it as short as possible.)
After unpacking, double-click eclipse.exe in the eclipse folder. On the workspace selection screen, leave the defaults and press the "Start" button.
Source preparation
After starting eclipse, the package explorer screen is displayed, so Press the "Create Project ..." link. From the window that appears, select "Dynamic Web Project" and press "Next".
Give the project name (LibertyCounter this time) and select Java8 as the target runtime. (It doesn't have to be Java8 ...) Then press the "Finish" button.
The Package Explorer will be displayed, so expand the project tree displayed there. Right-click in the src part> select "New"> "Class".
Here, the package name is counter and the class name is Counter. Specify up to that point and press "Finish".
Counter.java appears in the Package Explorer tree, and the Counter.java source appears in the right pane.
Overwrite that source window with the following source. The source itself is Deploy an existing JDBC application to Liberty (https://www.ibm.com/support/knowledgecenter/en/SSEQTP_liberty/com.ibm.websphere.wlp.doc/ae/twlp_dep_jdbc.html). ) Is based on the one described in. I will post the full text first, but after that I will pick up the point part and supplement it.
Counter.java
package counter;
import java.io.*;
import java.net.InetAddress;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.annotation.Resource;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.WebServlet;
import javax.sql.DataSource;
/**
* Servlet implementation class Counter
*/
@WebServlet("/Counter")
public class Counter extends HttpServlet {
@Resource(name = "jdbc/sample")
private DataSource ds1;
private Connection con = null;
private String hostname = null;
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public Counter() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
hostname = getHostName();
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<H1>Response from : "+ hostname +"</H1>\n");
try {
con = ds1.getConnection();
Statement stmt = null;
stmt = con.createStatement();
// check if hostname exists
ResultSet result = stmt.executeQuery("select distinct hostname from test01 where hostname='"+hostname+"'");
if( !result.next() ) {
out.println("Insert hostname into test01<br>\n");
stmt.executeUpdate("insert into test01 values ('"+hostname+"','1')");
} else {
out.println("Update hostname access count in test01<br>\n");
stmt.executeUpdate("update test01 set count=count+1 where hostname='"+hostname+"'");
}
ResultSet result2 = stmt.executeQuery("select * from test01");
while(result2.next()) {
out.println("<font size=\"+2\">"+result2.getString(1)+" : </font><font size=\"+2\" color=\"red\">"+result2.getInt(2)+"</font><br>\n");
}
}
catch (SQLException e) {
e.printStackTrace();
}
finally {
if (con != null){
out.println("<H1>DB2 Output Completed</H1>\n");
try{
con.close();
}
catch (SQLException e) {
e.printStackTrace();
}
}
}
}
/**
* getHostName
*
*/
public static String getHostName() {
try {
return InetAddress.getLocalHost().getHostName();
}catch (Exception e) {
e.printStackTrace();
}
return "UnknownHost";
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
The following is an excerpt.
Access with / Counter. Also, use jdbc / sample as a JDBC resource for DB connection. (Hard code ...)
@WebServlet("/Counter")
public class Counter extends HttpServlet {
@Resource(name = "jdbc/sample")
In the doGet method, use getHostName of the private method I am getting the host name. Also, as a response, the character string is stored in the form of solid HTML.
hostname = getHostName();
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<H1>Response from : "+ hostname +"</H1>\n");
Get a connection to the DB. This area is a magical target.
try {
con = ds1.getConnection();
Statement stmt = null;
stmt = con.createStatement();
The first thing to do is to use the select distinct ... SQL statement to see if hostname is already registered.
If it cannot be obtained (that is, the first access), the ʻInsert statement stores the host name and the data 1 in the table. If so, the count column is +1 in the ʻUpdate statement.
// check if hostname exists
ResultSet result = stmt.executeQuery("select distinct hostname from test01 where hostname='"+hostname+"'");
if( !result.next() ) {
out.println("Insert hostname into test01<br>\n");
stmt.executeUpdate("insert into test01 values ('"+hostname+"','1')");
} else {
out.println("Update hostname access count in test01<br>\n");
stmt.executeUpdate("update test01 set count=count+1 where hostname='"+hostname+"'");
}
Then we get all the data in the table and store it in the response variable in HTML format.
ResultSet result2 = stmt.executeQuery("select * from test01");
while(result2.next()) {
out.println("<font size=\"+2\">"+result2.getString(1)+" : </font><font size=\"+2\" color=\"red\">"+result2.getInt(2)+"</font><br>\n");
That's all for the logical part. If you are interested in other parts, please check.
War file output
Originally, it is a place to test with tomcat etc. registered in eclipse, but Skip that area and output the war file.
Right-click on the LibertyCounter project and select Export.
Open a folder on the web, select "WAR File" and press "Next".
Click the "Browse" button, specify the output destination folder / file name, and then press "Finish". The WAR file is output.
Thank you for your hard work. That's all for this time, and next time we will perform [7. Preparing the WebSphere Liberty container].
←: I tried running the DB access app on IKS + Db2 on IBM Cloud (5. Db2 on IBM Cloud preparation) ↑: I tried running the DB access app on IKS + Db2 on IBM Cloud (1. Overview) →: I tried running the DB access app on IKS + Db2 on IBM Cloud (7. Preparing the WebSphere Liberty container)
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