java协议写一个监视器监听数据库表的添加并获取新增的数据

这个问题可以通过使用Java的JDBC API和JDK提供的数据库事件API解决。

首先，你需要使用JDBC API连接到你的数据库。假设你已经有了一个名为"testdb"的数据库，数据库用户名为"root"，密码为"password"，并且你要监视名为"users"的表。

String url = "jdbc:mysql://localhost:3306/testdb";
String user = "root";
String password = "password";

Connection conn = DriverManager.getConnection(url, user, password);
Statement stmt = conn.createStatement();

接下来，你需要注册一个事件侦听器以接收数据库事件通知。Java提供了一个名为"javax.sql.DataSource"的接口，它可以让你向数据库注册事件侦听器。

DataSource ds = (DataSource) conn;
Connection eventConn = ds.getConnection();

String ddl = "CREATE TABLE IF NOT EXISTS testdb.users (id INT PRIMARY KEY AUTO_INCREMENT, name VARCHAR(50));";
stmt.execute(ddl);

DatabaseMetaData dbmd = eventConn.getMetaData();
String[] types = {"TABLE"};
ResultSet rs = dbmd.getTables(null, null, null, types);
while (rs.next()) {
    String tableName = rs.getString("TABLE_NAME");
    if ("users".equalsIgnoreCase(tableName)) {
        ((EventSource) eventConn).addStatementEventListener(new MyStatementEventListener());
        ((EventSource) eventConn).addRowSetEventListener(new MyRowSetEventListener());
    }
}

在这里，我们使用了"DatabaseMetaData"接口获取了所有的表名，并遍历这些表来查找我们要监视的表"users"。如果找到了这个表，我们就向数据库注册了两个事件侦听器："MyStatementEventListener"和"MyRowSetEventListener"。这两个事件侦听器分别用于监听SQL语句执行事件和结果集变化事件。

实现事件侦听器。

class MyStatementEventListener implements StatementEventListener {
    @Override
    public void statementClosed(StatementEvent event) {
        System.out.println("Statement closed: " + event.getSource());
    }

    @Override
    public void statementErrorOccurred(StatementEvent event) {
        System.out.println("Statement error occurred: " + event.getSource());
    }

    @Override
    public void statementExecuted(StatementEvent event) {
        System.out.println("Statement executed: " + event.getSource());
    }
}

class MyRowSetEventListener implements RowSetEventListener {
    @Override
    public void cursorMoved(RowSetEvent event) {
        System.out.println("Cursor moved: " + event.getSource());
    }

    @Override
    public void rowChanged(RowSetEvent event) {
        System.out.println("Row changed: " + event.getSource());
    }

    @Override
    public void rowSetChanged(RowSetEvent event) {
        System.out.println("Row set changed: " + event.getSource());
        try (ResultSet rs = event.getSource().getOriginal()) {
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                System.out.println("New row added: " + id + ", " + name);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

在这里，我们实现了两个事件侦听器："MyStatementEventListener"和"MyRowSetEventListener"。"MyStatementEventListener"用于监听SQL语句执行事件，"MyRowSetEventListener"用于监听结果集变化事件。当有新的数据添加到"users"表时，"MyRowSetEventListener"会收到"rowSetChanged"事件，并从结果集中获取新的数据。

最后，关闭数据库连接。

stmt.close();
conn.close();
eventConn.close();

完整的代码示例：

import java.sql.*;
import javax.sql.*;

class MyStatementEventListener implements StatementEventListener {
    @Override
    public void statementClosed(StatementEvent event) {
        System.out.println("Statement closed: " + event.getSource());
    }

    @Override
    public void statementErrorOccurred(StatementEvent event) {
        System.out.println("Statement error occurred: " + event.getSource());
    }

    @Override
    public void statementExecuted(StatementEvent event) {
        System.out.println("Statement executed: " + event.getSource());
    }
}

class MyRowSetEventListener implements RowSetEventListener {
    @Override
    public void cursorMoved(RowSetEvent event) {
        System.out.println("Cursor moved: " + event.getSource());
    }

    @Override
    public void rowChanged(RowSetEvent event) {
        System.out.println("Row changed: " + event.getSource());
    }

    @Override
    public void rowSetChanged(RowSetEvent event) {
        System.out.println("Row set changed: " + event.getSource());
        try (ResultSet rs = event.getSource().getOriginal()) {
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                System.out.println("New row added: " + id + ", " + name);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

public class DatabaseMonitor {
    public static void main(String[] args) throws Exception {
        String url = "jdbc:mysql://localhost:3306/testdb";
        String user = "root";
        String password = "password";

        Connection conn = DriverManager.getConnection(url, user, password);
        Statement stmt = conn.createStatement();

        DataSource ds = (DataSource) conn;
        Connection eventConn = ds.getConnection();

        String ddl = "CREATE TABLE IF NOT EXISTS testdb.users (id INT PRIMARY KEY AUTO_INCREMENT, name VARCHAR(50));";
        stmt.execute(ddl);

        DatabaseMetaData dbmd = eventConn.getMetaData();
        String[] types = {"TABLE"};
        ResultSet rs = dbmd.getTables(null, null, null, types);
        while (rs.next()) {
            String tableName = rs.getString("TABLE_NAME");
            if ("users".equalsIgnoreCase(tableName)) {
                ((EventSource) eventConn).addStatementEventListener(new MyStatementEventListener());
                ((EventSource) eventConn).addRowSetEventListener(new MyRowSetEventListener());
            }
        }

        stmt.close();
        conn.close();
        eventConn.close();
    }
}
``