java - sqlq 无法解析为变量

Question

我在下面程序的“ResultSet rs = st.executeQuery(sqlq)”行中的 Eclipse 中收到错误“sqlq 无法解析为变量”。请帮助我解决同样的问题。提前致谢!

//package searchbook;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.util.*;

public class SearchBook extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException,IOException{
response.setContentType("text/html"); 
HttpSession session = request.getSession(true);
List booklist=new ArrayList();
Connection con = null;

String url = "jdbc:odbc:Driver={Microsoft Access Driver (*.mdb, *.accdb)};DBQ=" + "C:\\users\\ppreeti\\executive_db.accdb";

String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
String user = "";
String pass = "";
String category="";
category=request.getParameter("input");
String sqlquery="select   Index1.link_id "    
        + "FROM Index1 "
        + " WHERE  Index1.index_name LIKE '%"+category+"%'  ";
try
    {
        Class.forName(driver);
        con = DriverManager.getConnection(url, user, pass);
            try{
                Statement st = con.createStatement();
                System.out.println("Connection created");
                ResultSet rs = st.executeQuery(sqlquery);
                System.out.println("Result retreived  ");
            }
            catch (SQLException s)
            {
                System.out.println("SQL statement is not executed! "+ s);
            }
        }
    catch (Exception e){
        e.printStackTrace();
    }
if(sqlquery.equals("1"))
{
String sqlq="select Section.Section_Name , Report.Report_Name , Report.Link, Contact.Contact_Name, Metrics.Metric_Name "
        + "FROM Section , Report , Contact,Metrics "
        + "WHERE Report.Contact_ID=Contact.Contact_ID and Report.Section_ID=Section.Section_ID  "
        + "and Report.Report_ID IN (SELECT Metrics.Report_ID FROM Metrics  WHERE Metrics.Metric_Name = Report.Report_ID') and Metrics.Metric_Segment = 'M' ";
}

try
{
    Class.forName(driver);
    con = DriverManager.getConnection(url, user, pass);
        try
            {
            Statement st = con.createStatement();
            System.out.println("Connection created");
            ResultSet rs = st.executeQuery(sqlq);
            System.out.println("Result retreived  ");
            while (rs.next())
            {
            List<String> book=new ArrayList<String>();

            String Name=rs.getString("Section_Name");
            String reportName=rs.getString("Report_Name");
            String link=rs.getString("Link");
            String contactName=rs.getString("Contact_Name");
            String metricName=rs.getString("Metric_Name");
            //String reportId=rs.getString("Report_ID");

            /*String ind_id=rs.getString("index_name");
            String ind_name=rs.getString("link_id");*/

            book.add(Name);
            book.add(reportName);
            book.add(link);
            book.add(contactName);
            book.add(metricName);
            //book.add(reportId);

            /*book.add(ind_id);
            book.add(ind_name);*/

            booklist.add(book);
            }
        }
        catch (SQLException s)
        {
            System.out.println("SQL statement is not executed! "+ s);
        }
    }
catch (Exception e) {
e.printStackTrace();
}
request.setAttribute("booklist",booklist); 
RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/searchbook.jsp");
dispatcher.forward(request, response); 
}
}

Answer 1

您在 if 范围内声明 sqlq，因此当您离开该 block (由 {} 分隔)时，它不会可访问。

您可以尝试在 if block 之外定义 sqlq:

String sqlq = "";

if (...) {
    sqlq = ...;
}