stevenson1017(明月) 你好:
我按照你的方法去做了在前面加了<%@ page import="DatabaseConn"%>
报错:org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: -1 in the jsp file: nullGenerated servlet error:
[javac] Compiling 1 source fileD:\Apache Group\Tomcat5\work\Catalina\localhost\dcs\org\apache\jsp\upload\text_005fdb_jsp.java:9: '.' expected
import DatabaseConn;
^
我按照你的方法去做了在前面加了<%@ page import="DatabaseConn"%>
报错:org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: -1 in the jsp file: nullGenerated servlet error:
[javac] Compiling 1 source fileD:\Apache Group\Tomcat5\work\Catalina\localhost\dcs\org\apache\jsp\upload\text_005fdb_jsp.java:9: '.' expected
import DatabaseConn;
^
解决方案 »
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你试着把bean.class文件放到web-inf\classes\package_name\bean.class
<jsp:useBean id="XX" class="package_name.bean"/>
import date;看看你的DatabaseConn在那个包里,将其写全了。
<%@ page import="lguo.DatabaseConn"%>
<jsp:useBean id="aaa" class="lguo.DatabaseConn" scope="page" >
</jsp:useBean>
<% ResultSet rst;
String sql="";
try{
// Connection conn=DatabaseConn.getConnection();
sql = "select * from [file]";
rst = aaa.executeQuery(sql);
while(rst.next()){
out.println(rst.getString(1));
}
}catch(Exception e) {
out.println(e);
}
%>
执行后网页出现java.lang.NullPointerException
import javax.naming.*;
import javax.sql.DataSource;
//一个用于查找数据源的工具类。
public class DatabaseConn{
private Connection con=null;
private Statement stmt=null;
ResultSet rst=null;public ResultSet executeQuery(String sql) throws Exception
{
rst=null;
try
{
Context initCtx = new javax.naming.InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
DataSource ds = (DataSource)envCtx.lookup("jdbc/dcs");
con=ds.getConnection();
stmt=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_READ_ONLY);
rst=stmt.executeQuery (sql);
}
catch(SQLException e){throw e;}
catch(NamingException e){throw e;}return rs;
}
//执行Insert,Update语句
public void executeUpdate(String sql) throws Exception
{
stmt = null;
rst=null;
try
{
Context initCtx = new javax.naming.InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
DataSource ds = (DataSource)envCtx.lookup("jdbc/dcs");
con=ds.getConnection();
stmt=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_READ_ONLY);
stmt.executeQuery(sql);
stmt.close();
con.close();
}
catch(SQLException ex)
{
System.err.println("执行SQL语句出错: " + ex.getMessage());
}
}
// 关闭stmt和关闭连接
public void close_all()
{
try{
stmt.close();
con.close();
}
catch(SQLException e){e.printStackTrace();}
}
}
Context initCtx = new javax.naming.InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
DataSource ds = (DataSource)envCtx.lookup("jdbc/dcs");
con=ds.getConnection();
import javax.naming.*;
import javax.sql.DataSource;
//一个用于查找数据源的工具类。
public class DBPool {
private Context initCtx;
private Context envCtx;
private DataSource ds;
private Connection conn=null;
private Statement stmt=null;
public ResultSet rs=null; public DBPool() {
try {
System.out.println("DBPool");
initCtx = new javax.naming.InitialContext();
envCtx = (Context) initCtx.lookup("java:comp/env");
ds = (DataSource)envCtx.lookup("jdbc/bn");
} catch(NamingException ne) {
System.out.println("数据库连接池初始化失败! \n " + "DBPool: " + ne );
}
} public ResultSet executeQuery(String sql) throws Exception
{
rs=null;
System.out.println("executeQuery");
try
{
conn = ds.getConnection();
stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_READ_ONLY);
rs = stmt.executeQuery (sql);
}
catch(SQLException e){throw e;}
return rs;
}
//执行Insert,Update语句
public int executeUpdate(String sql) throws Exception
{
rs=null;
int i = 0;
try
{
conn = ds.getConnection();
stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
i = stmt.executeUpdate(sql);
close_all() ;
}
catch(SQLException ex)
{
System.err.println("执行SQL语句出错: " + ex.getMessage());
close_all();
return 0;
}
return i;
}
// 关闭stmt和关闭连接
public void close_all()
{
try{
stmt.close();
conn.close();
} catch(SQLException e) {
e.printStackTrace();
}
}
}