java - 我无法让jsp执行SQL更新语句

Question

我试图让jsp从“update.jsp”上的表单获取用户输入，并运行更新语句来更新数据库条目并在“display.jsp”上显示结果。 我使用 eclipse 作为我的 IDE，使用 oracle 作为我的数据库服务器
之前，我已经成功执行了一条 select 语句(作为测试)。所以，我确信与数据库的连接没有问题
这是用于“update.jsp”(表单)的代码

<FORM ACTION="display.jsp">
    <label>Semester:
        <select name="semester_form">
            <option selected="semester">Semester Select</option>
            <%//public String input_semester=semester; %>

            <option value='Spring'>Springy</option>
            <option value='January Intersession'>January Intersession</option>
            <option value='Fall'>Fall</option>
            <option value='Summer ALL'>Summer ALL</option>
            <option value='Summer00'>Summer00</option>
            <option value='Summer02'>Summer02</option>
            <option value='Summer01'>Summer01</option>

这是我在创建数据库时使用的代码

CREATE TABLE SEMESTER_SCHEDULE_READER ( 
    SEMESTER_ID     VARCHAR2(2) NULL,
    START_DATE      DATE NULL,
    END_DATE        DATE NULL,
    SEMESTER_NAME   VARCHAR2(25) NULL,
    SEMESTER        VARCHAR2(8) NULL 
)

现在这是正在使用的“display.JSP”代码

Connection conn = null;
try {
    // 1. Load the driver
    Class.forName(driver);

    // myusername and mypassword are declared in a file called username.jsp

    // 2. Define the connection URL
    // 3. Establish the connection
    conn = DriverManager.getConnection(
            url,
            myusername,
            mypassword);


    // 4. Create a statement object
    Statement stmt = conn.createStatement();
    PreparedStatement pstatement = null;
    int updateQuery = 0;

    // 5. Execute a query

    String semester = request.getParameter("semester_form");
    session.putValue("semester_form", semester);
    String start_date = request.getParameter("startDate_form");
    String end_date = request.getParameter("endDate_form");
    //ResultSet rs = stmt.executeQuery("select * from SEMESTER_SCHEDULE_READER  where semeStER_NAME='"+semester+"'");
    conn.setAutoCommit(false);

    ResultSet rs = stmt.executeQuery("UPDATE SEMESTER_SCHEDULE_READER SET START_DATE= to_date('" + start_date + "', 'DD-MON-YY') WHERE SEMESTER='" + semester + "'");

    conn.commit();


    // printing a welcom message 
    out.println("<H1>You have successfully updated the semester schedule</H1><br>");

    //Print start of table and column headers
    out.println("<TABLE width = 600 CELLSPACING=\"0\" CELLPADDING=\"3\" BORDER=\"2\">");
    out.println("<TR><TH>Semester Name</TH><TH>Start date</TH><TH>End date</TH></TR>");

    // 6. Process result
    //column names and Data types has to match Db columns
    while (rs.next()) {
        out.println("<TR>");
        out.println("<TD>" + rs.getString("SEMESTER_NAME") + "</TD>");
        out.println("<TD>" + rs.getString("START_DATE") + "</TD>");
        out.println("<TD>" + rs.getString("END_DATE") + "</TD>");


        out.println("</TR>");
    }

    out.println("</TABLE>");
} catch (SQLException e) {
    // Do exception catch such as if connection is not made or 
    // query is not set up properly
    out.println("SQLException: " + e.getMessage() + "<BR>");
    while ((e = e.getNextException()) != null)
        out.println(e.getMessage() + "<BR>");
} catch (ClassNotFoundException e) {
    out.println("ClassNotFoundException: " + e.getMessage() + "<BR>");
} finally {
    // 7. Close connection; Clean up resources
    if (conn != null) {
        try {
            conn.close();
        } catch (Exception ignored) {
        }
    }
}
 %>

Answer 1

ResultSet rs = stmt.executeQuery(...)

应替换为

int results = stmt.executeUpdate(...)

executeQuery 在执行查询(选择)时使用，但 executeUpdate 在执行会更改数据库的操作时使用(插入、更新、删除)。