Java Community | Help. Code. Learn.•9mo ago

Database Connection Pooling

I need to implement a simple connection pooling mechanism for my application. The problem is I have almost no knowledge working with database connections. What things should I take into account? Is there any lightweight library out there? I expect the code to open as few connections as possible.

8 Replies

JavaBot•9mo ago

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Defective•9mo ago

Here is my current approach:

public final class ConnectionPool {
    private final String url, username, password;

    public static class Builder {

        private String url;
        private String username;
        private String password;

        public Builder setUrl(String url) {
            this.url = url;
            return this;
        }

        public Builder setUsername(String username) {
            this.username = username;
            return this;
        }

        public Builder setPassword(String password) {
            this.password = password;
            return this;
        }

        public ConnectionPool build() {
            return new ConnectionPool(url, username, password);
        }

        public Builder(String url) {
            this.url = url;
        }
    }

    private final List<Connection> availableConnections = new ArrayList<>();
    private final List<Connection> usedConnections = new ArrayList<>();

    private ConnectionPool(String url, String username, String password) {
        this.url = url;
        this.username = username;
        this.password = password;
    }

    public Connection getConnection() throws SQLException {
        Connection con = null;
        if (!availableConnections.isEmpty()) {
            con = availableConnections.get(0);
            availableConnections.remove(0);
            try {
                if (!con.isValid(1000))
                    throw new SQLException();
                usedConnections.add(con);
            } catch (Exception e) {
                con = null;
            }
        }

        if (con == null) {
            con = DriverManager.getConnection(url, username, password);
            usedConnections.add(con);
        }

        return con;
    }

    public boolean release(Connection con) {
        if (usedConnections.contains(con)) {
            usedConnections.remove(con);
            availableConnections.add(con);
            return true;
        }
        return false;
    }
}

public final class ConnectionPool {
    private final String url, username, password;

    public static class Builder {

        private String url;
        private String username;
        private String password;

        public Builder setUrl(String url) {
            this.url = url;
            return this;
        }

        public Builder setUsername(String username) {
            this.username = username;
            return this;
        }

        public Builder setPassword(String password) {
            this.password = password;
            return this;
        }

        public ConnectionPool build() {
            return new ConnectionPool(url, username, password);
        }

        public Builder(String url) {
            this.url = url;
        }
    }

    private final List<Connection> availableConnections = new ArrayList<>();
    private final List<Connection> usedConnections = new ArrayList<>();

    private ConnectionPool(String url, String username, String password) {
        this.url = url;
        this.username = username;
        this.password = password;
    }

    public Connection getConnection() throws SQLException {
        Connection con = null;
        if (!availableConnections.isEmpty()) {
            con = availableConnections.get(0);
            availableConnections.remove(0);
            try {
                if (!con.isValid(1000))
                    throw new SQLException();
                usedConnections.add(con);
            } catch (Exception e) {
                con = null;
            }
        }

        if (con == null) {
            con = DriverManager.getConnection(url, username, password);
            usedConnections.add(con);
        }

        return con;
    }

    public boolean release(Connection con) {
        if (usedConnections.contains(con)) {
            usedConnections.remove(con);
            availableConnections.add(con);
            return true;
        }
        return false;
    }
}

What can I improve here? Is the code even remotely "okay"?

Unknown User•9mo ago

Message Not Public

Defective•9mo ago

Thank you, I will check it out. I hope it is "lightweight" in that it takes least amount of space possible in the finished application

Unknown User•9mo ago

Message Not Public

Defective•9mo ago

Yeah, but I don't want to keep more connections open than needed at the given time Yes, looks nice. I will try it out Perfect! That's exactly what I was looking for, thank you!

JavaBot•9mo ago

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JavaBot•9mo ago

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