servletgrade.java

在线教育平台： 从小学

package edu;

import java.io.IOException;
import java.sql.SQLException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class Servletgrade extends javax.servlet.http.HttpServlet implements
		javax.servlet.Servlet {
	public void doGet(HttpServletRequest req, HttpServletResponse res)
			throws ServletException, IOException {
		int id = 0;
		HttpSession session = req.getSession(true);
		String sort = null;
		try {
			sort = session.getAttribute("sort").toString();
		} catch (NullPointerException e) {
		}
		int success = 0;
		String action = null;
		action = req.getParameter("action");
		try {
			id = Integer.valueOf(req.getParameter("grade_id")).intValue();
		} catch (NumberFormatException e) {
		}
		GradeBean grades = null;
		// String message = "";
		if (sort.equals("admin")) {
			if ("new".equalsIgnoreCase(action)) {
				grades = doNew(req, res);

				sendBean(req, res, grades, "/addclass.jsp");
			}

			if ("update".equalsIgnoreCase(action)) {
				try {
					grades = doUpdate(req, res, id);

					sendBean(req, res, grades, "/addclass.jsp");
				} catch (SQLException e) {
				}
			}

			if ("delete".equalsIgnoreCase(action)) {

				try {
					success = doDelete(id);
				} catch (SQLException e) {
				}

				if (success != 1) {
					doError(req, res, "删除失败. Rows affected: " + success);
				} else {
					res.sendRedirect("addclass.jsp");
				}
			}
		} else
			doError(req, res, "你无权操作，或你还没有登陆！");
	}

	public GradeBean doNew(HttpServletRequest req, HttpServletResponse res)
			throws ServletException, IOException {

		GradeBean grades = new GradeBean();
		String grade = new String(req.getParameter("grade").getBytes(
				"ISO8859_1"));
		grades.setGrade(grade);
		grades.addGrade();
		return grades;
	}

	public GradeBean doUpdate(HttpServletRequest req, HttpServletResponse res,
			int grade_id) throws ServletException, IOException, SQLException {
		GradeBean grades = new GradeBean();

		String grade = new String(req.getParameter("grade").getBytes(
				"ISO8859_1"));
		if (isTrue(req, res, grade)) {
			grades.setId(grade_id);
			grades.setGrade(grade);
			grades.updateGrade();
		}
		return grades;
	}

	public int doDelete(int id) throws SQLException {
		int num = 0;
		GradeBean grades = new GradeBean();
		num = grades.deleteGrade(id);
		return num;
	}

	public void sendBean(HttpServletRequest req, HttpServletResponse res,
			GradeBean grades, String target) throws ServletException,
			IOException {
		req.setAttribute("grades", grades);
		try {
			RequestDispatcher rd = req.getRequestDispatcher(target);
			rd.forward(req, res);
		} catch (Throwable t) {
		}
	}

	public void doError(HttpServletRequest req, HttpServletResponse res,
			String str) throws ServletException, IOException {
		req.setAttribute("problem", str);
		try {
			RequestDispatcher rd = req
					.getRequestDispatcher("/errorpage_ad.jsp");
			rd.forward(req, res);
		} catch (Throwable t) {
		}
	}

	public boolean isTrue(HttpServletRequest req, HttpServletResponse res,
			String grade) throws ServletException, IOException {
		boolean f = true;
		String message = "";
		if (grade == null || grade.equals("")) {
			f = false;
			message = "不能为空，请重新填写！";
			doError(req, res, message);
		}
		return f;
	}

	public void doPost(HttpServletRequest req, HttpServletResponse res)
			throws ServletException, IOException {
		doGet(req, res);
	}
}