如何将值从 servlet 传递到 Dao class 并执行操作和 return List/Arraylist 到 JSP 页面

Question

你好我是 JSP 开发新手，我需要一些关于 JSP MVC 编程的帮助我想从 Servlet 和 Dao 中传递一个值 class 我想接收它在 List 函数中执行操作并将第 return 个数组添加到 JSP 页面以使用 ..

Servlet

String company = "ABCD";
ObsBean ComName = new ObsBean();
ComName.setCompanyName(company);
dao.getComNotify(ComName);

Bean Class (ObsBean)

private String CompanyName;
public String getCompanyName() {
    return CompanyName;
}
public void setCompanyName(String CompanyName) {
    this.CompanyName = CompanyName;
}

**DAO Class (ObsDao) **

public List getComNotify(ObsBean ComName) {
    List<ObsBean> comNotify = new ArrayList<ObsBean>();
    String cname = ComName.getCompanyName();//getting from bean class by getter
    try {
        String sql = "SELECT * from ObsNotify where notto='"+cname+"'";
        ps = conn.prepareStatement(sql);
        rs = ps.executeQuery();

        while (rs.next()) {
            ObsBean userNotify = new ObsBean();

            userNotify.setNotifyName(rs.getString("notname"));
            userNotify.setNotifyBy(rs.getString("notby"));
            userNotify.setNotifyTo(rs.getString("notto"));
            userNotify.setNotifyDate(rs.getString("notdate"));

            comNotify.add(userNotify);
        }
    } 
    catch (Exception e) {
        out.print("Error for User Notification - : "+e);
    }
    return comNotify; 
}

IN JSP 页：

<%
ObsDao dao = new ObsDao();
List<ObsBean> ComNotify = dao.getComNotify();
for (ObsBean UserNotifi : ComNotify) {
.........
.........
}
%>

这是我的完整代码，但显示错误，为什么？

错误：

HTTP Status 500 – Internal Server Error

Type Exception Report

Message javax.servlet.ServletException: java.lang.NoSuchMethodError: com.ApexCorner.ModelDao.ObsDao.getComNotify()Ljava/util/List;

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

org.apache.jasper.JasperException: javax.servlet.ServletException: java.lang.NoSuchMethodError: com.ApexCorner.ModelDao.ObsDao.getComNotify()Ljava/util/List;
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:565)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:466)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

Answer 1

在您的 Dao class 中，CompanyName 应该有 getter 方法。所以试试下面的代码：

STRING COM = Comname; ,<-- 将此行更改为 String COM=Comname.getCompanyName();

Answer 2

根据您的代码，我假设您的 table 中的 "notto" 是一个公司名称，因此如果您的 sql 声明是正确的，我将重写您的代码如下：

public List getComNotify(ObsBean Comname) {
    List<ObsBean> comNotify = new ArrayList<ObsBean>();
    String COM = Comname.getcompanyname();
    try {
        String sql = "SELECT * from ObsNotify where notto='"+COM+"'";
        ps = conn.prepareStatement(sql);
        rs = ps.executeQuery();
        while (rs.next()) {
            ObsBean userNotify = new ObsBean();
            int totalRows = rs.getRow();

            userNotify.setNotifyName(rs.getString("notname"));
            userNotify.setNotifyBy(rs.getString("notby"));

            comNotify.add(userNotify);
        }
    } 
    catch (Exception e) {
        out.print("Error for User Notification - : "+e);
    }
    return comNotify; 
}

Comname是一个ObsBean类型的对象，你需要将公司名取回字符串才能应用到sql语句中，还要注意java是区分大小写的。

在JSP中做类似

的事情

<%
ObsDao dao = new ObsDao();
ObsDao otherdao = new ObsDao();
otherdao.setCompanyName("My company")
List<ObsBean> ComNotify = dao.getComNotify(otherdao);
for (ObsBean UserNotifi : ComNotify) {
.........
.........
}
%>

如何将值从 servlet 传递到 Dao class 并执行操作和 return List/Arraylist 到 JSP 页面

How to pass value from servlet to Dao class and perform operation and return List/ Arraylist to JSP page

java

jsp

dao

servlets

javabeans