package Db;
import java.sql.*;
import BK.*;
import java.util.*;

public class DbBook
{
     Connection Conn=null;
     Statement stmt=null;
     String SDBDriver="conn.jnetdirect.jsql.JSQLDriver";
     String sConnStr="jdbc:JSQLConnect://localhost/master";
     
     public DbBook()
     {
       try{
          Class.forName("conn.jnetdirect.jsql.JSQLDriver");
          Conn=DriverManager.getConnection(sConnStr,"sa","");
          stmt=Conn.createStatement();
         }catch(Exception e)
           {
           System.err.println(e);
            }
     }
     
     
     
     
     public  Vector getBook(int category,javax.servlet.jsp.jspWriter out,String keyword)
     {
        Vector vBook=new Vector();
        ResultSet rs;
        String SQL="";
        try{
           if(keyword==null)
              SQL="select * from book where category='"+category+"'";
           else {
            if(category==0)
               SQL="select * from book where name like'%"+keyword+"%'";
            else SQL="select * from book where category='"+category+"'and name like'%"+keyword+"%'";
             }
             rs=stmt.executeQuery(SQL);
             while(rs.next())
             {
                Book book=new Book();
                book.id=rs.getLong("id");
                book.name=rs.getString("name");
                book.price=rs.getFloat("price");
                book.category=rs.getInt("category");
                book.quantity=rs.getLong("quantity");
                vBook.add(book);
              }
              rs.close();
           }catch(Exception e)
                {
                     System.err.println(e);                
                 }
                 return vBook;
     }
     
     
     
     
     public BookgetABook(long saleid,javax.servlet.jsp.JspWriter out)
          {
           Book book=new Book();
              try{
                ResultSet rs=stmt.executeQuery("select * from book where id='"+saleid+"'");
                while(rs.next())
                {
                  book.id=rs.getLong("id");
                     book.name=rs.getString("name");
                     book.price=rs.getFloat("price");
                     book.category=rs.getInt("category");
                     book.quantity=rs.getLong("quantity");
                
                }
               rs.close();
              }catch(Exception e)
                         { 
                          System.err.println(e);
                         }
               return book;
            }
            
            
            
            
            
            
     public BookDetail getDetail(long bookid,javax.servlet.jsp.JspWriter out)
          {
           BookDetail bookdtl=new BookDetail();
           try{
                ResultSet rs=stmt.executeQuery("select * from book_detail where bookid='"+bookid+"'");
                while(rs.next())
                {
                  bookdtl.id=rs.getLong("id");
                  bookdtl.bookid=rs.getLong("bookid");
                     bookdtl.author=rs.getString("author");
                     bookdtl.introduce=rs.getString("introduce");
                     bookdtl.publisher=rs.getString("publisher");
                     bookdtl.pagenum=rs.getInt("pagenum");
                     bookdtl.edition=rs.getString("edition");
                
                }
               rs.close();
              }catch(Exception e)
                         { 
                          System.err.println(e);
                         }
               return bookdtl;
     }







     public decrease(long saleid,int num)
          {
          
           try{stmt.executeQuery("update book set quantity=quantity-"+num+" where id="+saleid+"");
               
              }catch(Exception e)
                         { 
                          System.err.println(e);
                         return null;
                         }
             
     }
     
     
     
     

     public long getBookId(String name)
          {
           ResultSet rs=null;
           long id=-1;
           try{rs=stmt.executeQuery("select * from book where name='"+name+"'");
                while(rs.next())
                {id=rs.getLong("id");}
          
               
              }catch(Exception e)
                         { 
                          System.err.println(e);
                          return -1l;
                         }
               return id;
     }





     public boolean addBook(int category,String name,String author,float price,String publisher,int pagenum,String edition,int quantity,String intro)
             
          {
           long saleid=-1l;
           ResultSet rs=null;
          
           try{rs=stmt.executeQuery("select * from book where name='"+name+"'");
                while(rs.next())
                {saleid=rs.getLong("id");}
               
               
              }catch(Exception e)
                         { 
                          System.err.println(e);
                          return false;
                         }
               if(saleid!=-1l){//ÒѾ­´æÔÚ
                    try{
                     stmt.executeUpdate("update book set quantity=quantity+"+quantity+" where id="+saleid);
                       }catch(Exception e){
                                System.err.println(e);
                                 return false;
                                          }
                              }else{
                                  try{
                      stmt.executeUpdate("insert into book_detail values('"+bookid+"','"+author+"','"+publisher+"','"+pagenum+"','"+edition+"','"+intro+"')");
                                      }catch(Exception e)
                                         {
                                     System.err.println(e);
                                      return false;
                                       }
                                       return true;
                                    }
                           
     }
     
     
     
     
     public boolean destroy()
     {
        try{
             Conn.close();      
            }catch(Exception e)
                  {
                  return false;
                   }
                 return true;
                  
     }
}

public decrease(long saleid,int num)
问题一样,还是没有返回类型,如果是不需要返回的,就写
public void decrease(long saleid,int num)
并且把下面出错的 return null删掉.

你的环境里没有JspWrite这个类,去载一个.
两个return的错误由上两个解决了.
最后一个错:在这个方法里bookid没有定义.其他地方都有定义为long的.这里漏了.
 

JBOSS我不懂,但起码你的java程序应该要import javax.servlet.jsp.*;
一般是不会有javax包的,我就是去sun载的.

public BookgetABook(long saleid,javax.servlet.jsp.JspWriter out)
漏一个空格,当然就认为没有返回类型了.
public Book getABook(long saleid,javax.servlet.jsp.JspWriter out)

1. public BookgetABook() 没有返回类型
2. public decrease() 没有返回类型
3,4,5. 加上import javax.servlet.jsp.*
6,7. 返回值不正确和1，2的错误有关