初学者的问题，在我的javabean中无法访问MySQL！！请各位指教！
我的javabean是这样的： public class DataBase {
public Connection conn;
public Statement stmt;
public ResultSet rs=null;
public String sqlStr=""; public DataBase() {
this.connect();
}
public boolean connect(){
try{
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
String url ="jdbc:mysql://localhost/BookStore?user=root&password=mm&useUnicode=true&characterEncoding=8859_1";
conn=DriverManager.getConnection(url);
stmt = conn.createStatement ();
}catch(Exception ee){
System.out.println("connect db error:"+ee.getMessage());
return false;
}
return true;
}
public static void main(String[] args) {
try{
DataBase db = new DataBase();
db.connect();
}catch(Exception e){
e.printStackTrace();
}
}
}
我的javabean是这样的： public class DataBase {
public Connection conn;
public Statement stmt;
public ResultSet rs=null;
public String sqlStr=""; public DataBase() {
this.connect();
}
public boolean connect(){
try{
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
String url ="jdbc:mysql://localhost/BookStore?user=root&password=mm&useUnicode=true&characterEncoding=8859_1";
conn=DriverManager.getConnection(url);
stmt = conn.createStatement ();
}catch(Exception ee){
System.out.println("connect db error:"+ee.getMessage());
return false;
}
return true;
}
public static void main(String[] args) {
try{
DataBase db = new DataBase();
db.connect();
}catch(Exception e){
e.printStackTrace();
}
}
}
type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: /bookshop/login.jsp(3,0) The value for the useBean class attribute bookshop.run.login is invalid.
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:40)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:407)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:148)
org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1175)
org.apache.jasper.compiler.Node$UseBean.accept(Node.java:1117)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2166)
org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2216)
org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2222)
org.apache.jasper.compiler.Node$Root.accept(Node.java:457)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2166)
org.apache.jasper.compiler.Generator.generate(Generator.java:3321)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:199)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:296)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:277)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:265)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:564)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:302)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.26 logs.
我按照下面的思路解决，还是有问题啊！
1. 在编译 JSP 时（不是运行时），指定的 Bean 类没找到
2. Bean 虽然找到了，但是它不是 public 的，或者找到的 class 文件是 interface 或抽象类
3. Bean 类中没有 public 的默认构建函数
都要烦死了！