idea写一个Servlet以实现增删改查 Emp表，连接oracle数据库

好的，这个问题很棒。为了实现增删改查Emp表的Servlet，需要进行以下步骤：

1. 首先，需要建立一个Emp类，包含Emp表中每个字段的属性，如id、name、age等。

2. 然后，需要在Servlet中建立Oracle数据库连接，在doGet或doPost方法中实现增删改查操作。

3. 对于查询操作，可以使用SELECT语句从Emp表中获取数据，并将结果集存储在List<Emp>对象中。

4. 对于插入操作，可以使用INSERT语句将新的Emp对象插入到Emp表中。

5. 对于更新操作，可以使用UPDATE语句更新Emp表中指定的字段。

6. 对于删除操作，可以使用DELETE语句从Emp表中删除指定的数据。

下面是一个简单的示例代码，演示如何实现增删改查Emp表的Servlet:

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/EmpServlet")
public class EmpServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    private Connection conn = null;
    private PreparedStatement pstmt = null;
    private ResultSet rs = null;

    private String url = "jdbc:oracle:thin:@localhost:1521:orcl";
    private String user = "scott";
    private String password = "tiger";

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String method = request.getParameter("method");

        if ("add".equals(method)) {
            addEmp(request, response);
        } else if ("delete".equals(method)) {
            deleteEmp(request, response);
        } else if ("update".equals(method)) {
            updateEmp(request, response);
        } else if ("query".equals(method)) {
            queryEmp(request, response);
        }
    }

    private void addEmp(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String id = request.getParameter("id");
        String name = request.getParameter("name");
        String age = request.getParameter("age");
        String sql = "INSERT INTO Emp (id, name, age) VALUES (?, ?, ?)";

        try {
            conn = DriverManager.getConnection(url, user, password);
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, id);
            pstmt.setString(2, name);
            pstmt.setString(3, age);
            pstmt.executeUpdate();

            response.sendRedirect("index.jsp");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            closeAll();
        }
    }

    private void deleteEmp(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String id = request.getParameter("id");
        String sql = "DELETE FROM Emp WHERE id = ?";

        try {
            conn = DriverManager.getConnection(url, user, password);
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, id);
            pstmt.executeUpdate();

            response.sendRedirect("index.jsp");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            closeAll();
        }
    }

    private void updateEmp(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String id = request.getParameter("id");
        String name = request.getParameter("name");
        String age = request.getParameter("age");
        String sql = "UPDATE Emp SET name = ?, age = ? WHERE id = ?";

        try {
            conn = DriverManager.getConnection(url, user, password);
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, name);
            pstmt.setString(2, age);
            pstmt.setString(3, id);
            pstmt.executeUpdate();

            response.sendRedirect("index.jsp");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            closeAll();
        }
    }

    private void queryEmp(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<Emp> list = new ArrayList<Emp>();
        String sql = "SELECT * FROM Emp";

        try {
            conn = DriverManager.getConnection(url, user, password);
            pstmt = conn.prepareStatement(sql);
            rs = pstmt.executeQuery();

            while (rs.next()) {
                Emp emp = new Emp();
                emp.setId(rs.getString("id"));
                emp.setName(rs.getString("name"));
                emp.setAge(rs.getString("age"));
                list.add(emp);
            }

            request.setAttribute("list", list);
            request.getRequestDispatcher("list.jsp").forward(request, response);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            closeAll();
        }
    }

    private void closeAll() {
        try {
            if (rs != null) {
                rs.close();
            }
            if (pstmt != null) {
                pstmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

以上代码可能需要根据你的实际情况作一些修改，例如数据库连接信息、SQL语句等。