How to Convert Database Results into JSON Files

Pre-Requisite:

Create Mock Table "constomersInfo" in "ClassicModels" Database and insert some data.

CREATE DATABASE ClassicModels;

use ClassicModels;

CREATE TABLE CustomerInfo

(BookName varchar(50),

PurchasedDate date,

Amount int(50),

Location varchar(50));

INSERT INTO CustomerInfo values("selenium",CURRENT_DATE(),350,'Africa');

INSERT INTO CustomerInfo values("Java",CURRENT_DATE(),200,'Africa');

INSERT INTO CustomerInfo values("Python",CURRENT_DATE(),250,'Asia');

INSERT INTO CustomerInfo values("Jmeter",CURRENT_DATE(),150,'Asia');

INSERT INTO CustomerInfo values("C#",CURRENT_DATE(),300,'Asia');

select * from CustomerInfo where purchasedDate=CURDATE() and Location ='Asia';

Step 1: Retrieve Results from Database using JDBC

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

public class ConvertDBResult_JavaObject_JsonFile{

     public static void main(String[] args) throws SQLException {

          // 1) Create a connection

          Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/classicmodels", "root", "root");

          // 2) Create statement/Query

          Statement stmt = con.createStatement();

          String s = "select * from customerinfo  limit 1";

          // 3,4) Execute statement/Query & Store data in resultset

          ResultSet rs = stmt.executeQuery(s);

          CustomerDetails cd=new CustomerDetails();

         

          while (rs.next()) {

              String bookname = rs.getString("BookName");

              String purchasedate = rs.getString("PurchasedDate");

              int amount = rs.getInt("Amount");

              String location = rs.getString("Location");

              System.out.println(bookname + "   " + purchasedate + "      " + amount+"    "+location);

          }

          // 5) close connection

          con.close();

          System.out.println("Query executed.....");

     }

}

Step 2: Converts Data base Results into Java Object (Plain Old Java Object)  public class CustomerDetails {

     String bookname;

     String purchasedate;

     int amount;

     String location;

    

     public String getBookname() {

          return bookname;

     }

     public void setBookname(String bookname) {

          this.bookname = bookname;

     }

     public String getPurchasedate() {

          return purchasedate;

     }

     public void setPurchasedate(String purchasedate) {

          this.purchasedate = purchasedate;

     }

     public int getAmount() {

          return amount;

     }

     public void setAmount(int amount) {

          this.amount = amount;

     }

     public String getLocation() {

          return location;

     }

     public void setLocation(String location) {

          this.location = location;

     }

}

Modify JDBC Program which will use POJO (Plain Old Java Object) Class to retrieve data from Java Object.

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

public class ConvertDBResult_JavaObject_JsonFile{

     public static void main(String[] args) throws SQLException {

          // 1) Create a connection

          Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/classicmodels", "root", "root");

          // 2) Create statement/Query

          Statement stmt = con.createStatement();

          String s = "select * from customerinfo  limit 1";

          // 3,4) Execute statement/Query & Store data in resultset

          ResultSet rs = stmt.executeQuery(s);

          CustomerDetails cd=new CustomerDetails();

         

          while (rs.next()) {

              String bookname = rs.getString("BookName");

              String purchasedate = rs.getString("PurchasedDate");

              int amount = rs.getInt("Amount");

              String location = rs.getString("Location");

             

              cd.setBookname(bookname);

              cd.setPurchasedate(purchasedate);

              cd.setAmount(amount);

              cd.setLocation(location);

          }

          // 5) close connection

          con.close();

    

          System.out.println(cd.getLocation());

     }

}

Step 3: Convert Java Objects into JSON Files

            Maven Dependencies: Jackson Core, Jackson Databind, Jackson annotations

Single Java Object à Single JSON File:

import java.io.File;

import java.io.IOException;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import com.fasterxml.jackson.core.JsonGenerationException;

import com.fasterxml.jackson.databind.JsonMappingException;

import com.fasterxml.jackson.databind.ObjectMapper;

public class ConvertDBResult_JavaObject_JsonFile{

     public static void main(String[] args) throws SQLException, JsonGenerationException, JsonMappingException, IOException {

          // 1) Create a connection

          Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/classicmodels", "root", "root");

          // 2) Create statement/Query

          Statement stmt = con.createStatement();

          String s = "select * from customerinfo  limit 1";

          // 3,4) Execute statement/Query & Store data in resultset

          ResultSet rs = stmt.executeQuery(s);

          CustomerDetails cd=new CustomerDetails();

         

          while (rs.next()) {

              String bookname = rs.getString("BookName");

              String purchasedate = rs.getString("PurchasedDate");

              int amount = rs.getInt("Amount");

              String location = rs.getString("Location");

             

              cd.setBookname(bookname);

              cd.setPurchasedate(purchasedate);

              cd.setAmount(amount);

              cd.setLocation(location);

          }

          // 5) close connection

          con.close();

                  

          // Using Jakson API, Converting Java object into JSON File

          File jsonfile=new File("C:\\Users\\admin\\eclipse-workspace\\sdet\\custinfo.json");

         

          ObjectMapper om=new ObjectMapper();

          om.writeValue(jsonfile, cd);

         

          System.out.println("Done!");

         

     }

}

Multiple Java Objects à Multiple JSON Files:

import java.io.File;

import java.io.IOException;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.ArrayList;

import com.fasterxml.jackson.core.JsonGenerationException;

import com.fasterxml.jackson.databind.JsonMappingException;

import com.fasterxml.jackson.databind.ObjectMapper;

public class ConvertDBResults_JavaObjects_JsonFiles {

     public static void main(String[] args) throws SQLException, JsonGenerationException, JsonMappingException, IOException {

          // 1) Create a connection

          Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/classicmodels", "root", "root");

          // 2) Create statement/Query

          Statement stmt = con.createStatement();

          String s = "select * from customerinfo";

          // 3,4) Execute statement/Query & Store data in resultset

          ResultSet rs = stmt.executeQuery(s);

          ArrayList ar=new ArrayList();

         

          while (rs.next()) {

              String bookname = rs.getString("BookName");

              String purchasedate = rs.getString("PurchasedDate");

              int amount = rs.getInt("Amount");

              String location = rs.getString("Location");

             

              CustomerDetails cd=new CustomerDetails();

             

              cd.setBookname(bookname);

              cd.setPurchasedate(purchasedate);

              cd.setAmount(amount);

              cd.setLocation(location);

             

              ar.add(cd); // Adding all the objects to arraylist

          }

          //Using Jakson API, Converting all Java objects into JSON Files

         

          for(int i=0;i

          {

              File jsonfile=new File("C:\\Users\\admin\\eclipse-workspace\\sdet\\custinfo"+i+".json");

             

              ObjectMapper om=new ObjectMapper();

              om.writeValue(jsonfile,ar.get(i));

          }

                  

          System.out.println("Done!");

    

          con.close();

         

     }

}

Multiple Java Objects à Single JSON (Along with JSON Formatting):

package sdet;

import java.io.File;

import java.io.IOException;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.ArrayList;

import org.json.simple.JSONArray;

import org.json.simple.JSONObject;

import com.fasterxml.jackson.core.JsonGenerationException;

import com.fasterxml.jackson.databind.JsonMappingException;

import com.fasterxml.jackson.databind.ObjectMapper;

import com.google.gson.Gson;

public class ConvertDBResults_JavaObjects_SingleJsonFile {

     public static void main(String[] args) throws SQLException, JsonGenerationException, JsonMappingException, IOException {

          // 1) Create a connection

          Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/classicmodels", "root", "root");

          // 2) Create statement/Query

          Statement stmt = con.createStatement();

          String s = "select * from customerinfo";

          // 3,4) Execute statement/Query & Store data in resultset

          ResultSet rs = stmt.executeQuery(s);

          ArrayList ar=new ArrayList();

         

          while (rs.next()) {

              String bookname = rs.getString("BookName");

              String purchasedate = rs.getString("PurchasedDate");

              int amount = rs.getInt("Amount");

              String location = rs.getString("Location");

             

              CustomerDetails cd=new CustomerDetails();

             

              cd.setBookname(bookname);

              cd.setPurchasedate(purchasedate);

              cd.setAmount(amount);

              cd.setLocation(location);

             

              ar.add(cd); // Adding all the objects to arraylist

          }

          //Using Jakson API, Converting all Java objects into JSON Files

         

          JSONArray jsonr=new JSONArray(); //Required to add JSon string to Json array

         

          for(int i=0;i

          {

              //File jsonfile=new File("C:\\Users\\admin\\eclipse-workspace\\sdet\\custinfo"+i+".json");

              //ObjectMapper om=new ObjectMapper();

              //om.writeValue(jsonfile,ar.get(i));

             

              Gson g=new Gson();

              String JsonString=g.toJson(ar.get(i)); //Converts Java object into JSON String

             

              jsonr.add(JsonString); //Add JSon String to Json Array

          }

         

          JSONObject jo=new JSONObject();

          jo.put("data",jsonr);

         

          System.out.println(jo.toJSONString()); // added escape chars That's not right format

    

          String jsonFormattedString = jo.toJSONString().replace("\\\"", "\""); //removed escape chars

          System.out.println(jsonFormattedString); //still doubles quotes there. It's not exactly in Json format

         

          String finalJSONString=jsonFormattedString.replace("\"{","{").replace("}\"","}"); //Removes double quotes both the sides

          System.out.println(finalJSONString);

         

          System.out.println("Done!");

                  

          con.close();

         

     }

}

Step 4: Convert JSON to Java Object

import java.io.File;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonParseException;

import com.fasterxml.jackson.databind.JsonMappingException;

import com.fasterxml.jackson.databind.ObjectMapper;

public class JSONtoJavaObject {

     public static void main(String[] args) throws JsonParseException, JsonMappingException, IOException {

         

          ObjectMapper om=new ObjectMapper();

         

          File jsonfile=new File("C:\\Users\\admin\\eclipse-workspace\\sdet\\custinfo.json");

          CustomerDetails cd=om.readValue(jsonfile, CustomerDetails.class);

         

          System.out.println(cd.getBookname());

          System.out.println(cd.getAmount());

         

     }

}