I am working on a project in which I have three tables in a different database with different schemas. So that means I have three different connection parameters for those three tables to connect using JDBC-
Let's suppose-
For Table1-
Username:- A
Password:- B
URL: C
Columns-
ID1 String
Account1 String
For Table2-
Username:- P
Password:- Q
URL:- R
Columns-
ID2 String
Account2 String
For Table3-
Username:- T
Password:- U
URL:- V
Columns-
ID3 String
Account3 String
And I am supposed to insert in all the three tables or any one of them using JDBC.
Below are the three use cases I have-
- From the command prompt if suppose I am passing Table1 only, then I am suppose to insert only in Table1 columns by making connection to
Table1.
- And if I am passing Table1, Table2 from the command prompt then I am suppose to insert in both Table1 and Table2 columns by making
connection to Table1 and Table2.
- And if I am passing Table1, Table2 and Table3 then I am suppose to enter in all the three tables using there respective connection
parameter
I am not able to understand how to write code for the above particular scenario in such a cleaner way so that it can be extended in near future as well if I come up with four tables. I can have a one constant file which can store the SQL that needs to be executed for any of the three tables and some other constant thing as well.
public static void main(String[] args) {
}
class Task implements Runnable {
private Connection dbConnection = null;
private PreparedStatement preparedStatement = null;
public Task() {
}
@Override
public void run() {
dbConnection = getDbConnection();
//prepare the statement and execute it
}
}
private Connection getDBConnection() {
Connection dbConnection = null;
Class.forName(Constants.DRIVER_NAME);
dbConnection = DriverManager.getConnection( , , );
return dbConnection;
}
Can anyone provide some thoughts on this how should I proceed forward?
Note:-
Column in each table will differ a lot. Like in some tables, column can be 10 and in some other table, column can be 20.
Create databases.properties file with content like this:
# Table 1
table1.url: jdbc:mysql://localhost:3306/garden
table1.user: gardener
table1.password: shavel
table1.table: fruits
table1.column.id: fruitID
table1.column.color: fruitColor
table1.column.weight: fruitWeight
# ... More fruit columns here ...
# Table 2
table2.url: jdbc:mysql://otherhost:3306/forest
table2.user: forester
table2.password: axe
table2.table: trees
table2.column.id: treeID
table2.column.height: treeHeight
# ... More tree columns here ...
# ... More tables here ...
Then do something like this:
public static void main (String [] args)
{
Properties databasesProperties = new Properties ();
databasesProperties.load ("databases.properties");
for (String arg: args)
{
String url = databasesProperties.get (arg + ".url");
String user = databasesProperties.get (arg + ".user");
String password= databasesProperties.get (arg + ".password");
String table = databasesProperties.get (arg + ".table");
String columnPrefix = arg + ".column."
Map <String, String> columns = new HashMap <String, String> ();
for (String key: databasesProperties.stringPropertyNames ())
{
if (key.startsWith (columnPrefix))
columns.put (
key.substring (columnPrefix.length ()),
databasesProperties.get (key));
}
doInsert (url, user, password, table, columns);
}
}
Later you can always add more tables into your databases.properties file.
Save your Database properties in a class file DBPropery.java.
final class DBProperty
{
static String[] urls = {
"C",
"R",
"V"
}; //You can add more URLs here.
static String[] driver= {
"Driver1",
"Driver2",
"Driver3"
};//You can add more drivers string
static String[] table = {
"Table1",
"Table2",
"Table3"
};//You can add more table names here According to URLs mentioned in urls array.
static String[] user = {
"A",
"P",
"T"
};//You can add more user names here according to URls mentioned in urls array.
static String[] pwd = {
"B",
"Q",
"U"
};//You can add more Password here according to URls mentioned in urls array.
static String[] queries = {
"Query for Table1",
"Query for Table2",
"Query for Table3",
};//You can add more queries here for more tables according to URls mentioned in urls array.
static int[] columns ={
2,
2,
2
};//You can change the column numbers according to need . 0th index belongs to Table1 , 1 to table2....so on.
//If you add more tables , add corresponding columns count to next index.
static String[] columnValues ={
"1^John",
"34^Vicky",
"65^Ethen"
};//String at each index represents a row in corresponding table in table[] array. each column is seperated by delimiter "^".
}
Make all Changes in DBProperty.java file.
Then proceed with following class file
import java.sql.*;
import java.util.*;
class MultiTableInsert implements Runnable
{
Map<String,Integer> columnsInTable;
Map<String,String> tableDriver;
Map<String,String> rowForTable;
Map<String,String> queryForTable;
Map<String,String> urlForTable;
Map<String,String> userForTable;
Map<String,String> pwdForTable;
String[] tables ;
public MultiTableInsert(String... tables)//Loading all Database Settings here..
{
this.tables = tables;
columnsInTable = new LinkedHashMap<String,Integer>();
rowForTable = new LinkedHashMap<String,String>();
tableDriver = new LinkedHashMap<String,String>();
urlForTable = new LinkedHashMap<String,String>();
userForTable= new LinkedHashMap<String,String>();
pwdForTable = new LinkedHashMap<String,String>();
for (int i = 0 ; i < DBProperty.urls.length ; i++ )
{
try
{
tableDriver.put(DBProperty.table[i],DBProperty.driver[i]);
queryForTable.put(DBProperty.table[i],DBProperty.queries[i]);
columnsInTable.put(DBProperty.table[i],DBProperty.columns[i]);
rowForTable.put(DBProperty.table[i],DBProperty.columnValues[i]);
urlForTable.put(DBProperty.table[i],DBProperty.urls[i]);
userForTable.put(DBProperty.table[i],DBProperty.user[i]);
pwdForTable.put(DBProperty.table[i],DBProperty.pwd[i]);
}
catch (Exception ex)
{
ex.printStackTrace();
}
}
}
@Override
public void run()
{
insertIntoTable(tables);
}
private void insertIntoTable(String... tables)
{
for (String tble : tables )
{
Connection con = null;
PreparedStatement pStmt = null;
try
{
Class.forName(tableDriver.get(tble));
con = DriverManager.getConnection(urlForTable.get(tble),userForTable.get(tble),pwdForTable.get(tble));
pStmt = con.prepareStatement(queryForTable.get(tble));
int columns = columnsInTable.get(tble);
String sRow = rowForTable.get(tble);
StringTokenizer tokenizer = new StringTokenizer(sRow,"^");
for (int i = 0; i < columns ; i++)
{
pStmt.setString(i+1,(String)tokenizer.nextElement());
}
pStmt.execute();
}
catch (Exception ex)
{
ex.printStackTrace();
}
finally
{
try
{
con.close();
}catch (Exception ex){}
try
{
pStmt.close();
}catch (Exception ex){}
}
}
}
public static void main(String[] args)
{
int length = args.length;
int THREAD_COUNTS = 10;//Number of threads you want to start.
switch (length)
{
case 0:
System.out.println("Usage: javac MultiTableInsert Table1/Table2/Table3 <Table1/Table2/Table3> <Table1/Table2/Table3>");
System.exit(0);
case 1:
for (int i = 0 ; i < THREAD_COUNTS ; i++)
{
MultiTableInsert mti = new MultiTableInsert(args[0]);
Thread th = new Thread(mti,"Thread"+i);//Create New Thread
th.start(); //Start Thread
}
break;
case 2:
for (int i = 0 ; i < THREAD_COUNTS ; i++)
{
MultiTableInsert mti = new MultiTableInsert(args[0],args[1]);//Create New Thread
Thread th = new Thread(mti,"Thread"+i); //Start Thread
th.start();
}
break;
default:
for (int i = 0 ; i < THREAD_COUNTS ; i++)
{
MultiTableInsert mti = new MultiTableInsert(args[0],args[1],args[2]);//Create New Thread
Thread th = new Thread(mti,"Thread"+i); //Start Thread
th.start();
}
break;
}
}
}
