package connectionPool;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import javax.servlet.annotation.*;

@WebServlet("/ConnContext")
public class ConnContext extends HttpServlet {

    public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
        res.setContentType("text/html; charset=UTF-8");
        PrintWriter out = res.getWriter();

        // get/set connection pool and put it in Context object
        ServletContext context = req.getServletContext();
        ConnectionPool connPool = (ConnectionPool) context.getAttribute("connList");
        if (connPool == null) {
            System.out.println("Create connection pool.");
            connPool = new ConnectionPool();
            connPool.openDB(2);
            context.setAttribute("connList", connPool);
        }

        // get connection from connection pool:
        Connection con = connPool.getConnection();
        System.out.println("After getConnection() connList: " + connPool.size());

        // make current Thread wait for testing purpose
        try {
            Thread.sleep(10000); // 象徵意義：這個人在查資料，且用了好久，占掉一個Connection物件資源
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // get data via sql commands
        out.println(new HtmlSQLResult("SELECT * from emp2", con));

        // return connection back to connection pool:
        connPool.returnConnection(con);
        System.out.println("After returnConnection() connList: " + connPool.size());

        // wrap up the results
        context.setAttribute("connList", connPool);
    }

    @Override
    protected void doDelete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = req.getServletContext();
        ConnectionPool connPool = (ConnectionPool) context.getAttribute("connList");
        connPool.closeDB();
    }
}