4.这是用来测试的JSP代码:
<%@ page contentType="text/html; charset=" language="java" import="java.sql.*" errorPage="" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>无标题文档</title>
</head>
<jsp:useBean id="dissql" scope="page" class="balance.testBean"/>
<body>
<p>
<%
String KHH="",KHM="",ADDR="";
%>
</p>
<%
ResultSet rs = dissql.getdata();
while(rs.next())
{
KHH=rs.getString("KHH");
KHM=rs.getString("KHM");
ADDR=rs.getString("ADDR");
%>
<td><%=KHH%></td>
<td><%=KHM%></td>
<td><%=ADDR%></td>
<%
}
%>
</body>
</html>5.这是一个用来测试的BEAN:
package balancepack;import java.sql.*;public class testBean {
public ResultSet getdata(){
String sql="select KHH,KHM,ADDR from WL_KHCOD WHERE KHH='000000'";
sqlBean db= new sqlBean();
ResultSet rs = db.executeQuery(sql);
return rs;
}
}6.这是提示的问题:
org.apache.jasper.JasperException: Unsupported encoding:
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:94)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:404)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:154)
org.apache.jasper.compiler.JspUtil.getReader(JspUtil.java:1062)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:242)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:149)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:135)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:243)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:437)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:555)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:291)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
<%@ page contentType="text/html; charset=" language="java" import="java.sql.*" errorPage="" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>无标题文档</title>
</head>
<jsp:useBean id="dissql" scope="page" class="balance.testBean"/>
<body>
<p>
<%
String KHH="",KHM="",ADDR="";
%>
</p>
<%
ResultSet rs = dissql.getdata();
while(rs.next())
{
KHH=rs.getString("KHH");
KHM=rs.getString("KHM");
ADDR=rs.getString("ADDR");
%>
<td><%=KHH%></td>
<td><%=KHM%></td>
<td><%=ADDR%></td>
<%
}
%>
</body>
</html>5.这是一个用来测试的BEAN:
package balancepack;import java.sql.*;public class testBean {
public ResultSet getdata(){
String sql="select KHH,KHM,ADDR from WL_KHCOD WHERE KHH='000000'";
sqlBean db= new sqlBean();
ResultSet rs = db.executeQuery(sql);
return rs;
}
}6.这是提示的问题:
org.apache.jasper.JasperException: Unsupported encoding:
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:94)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:404)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:154)
org.apache.jasper.compiler.JspUtil.getReader(JspUtil.java:1062)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:242)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:149)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:135)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:243)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:437)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:555)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:291)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
jsp的开头的地方写错,所以抱Unsupported encoding:
charset至少要付一个值
<%@ page contentType="text/html; charset=" language="java"
->
<%@ page contentType="text/html; charset="UTF-8" language="java" 再试.国庆快乐^_^
但是现在又提示了这样的错误:
org.apache.jasper.JasperException: /testsql.jsp(1,48) equal symbol expected
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:83)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:402)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:126)
org.apache.jasper.compiler.Parser.parseAttribute(Parser.java:240)
org.apache.jasper.compiler.Parser.parseAttributes(Parser.java:190)
org.apache.jasper.compiler.Parser.parseAttributes(Parser.java:203)
org.apache.jasper.compiler.ParserController.getPageEncodingForJspSyntax(ParserController.java:443)
org.apache.jasper.compiler.ParserController.determineSyntaxAndEncoding(ParserController.java:413)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:197)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:149)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:135)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:243)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:437)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:555)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:291)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
还有,请您看看我的连接池写的有没有问题,这样处理对不对!因为这是第一次写,一点信心也没有,还有,这样写有没有问题,我刚看个文章,说不可以在连接池里直接把CON给CLOSE掉,是这样么?
try{
//conn.close();
conn = null;
}
catch(Exception end){
System.err.println("执行关闭Connection对象有错误:"+end.getMessage( ) );
System.out.print("执行执行关闭Connection对象有错误:有错误:"+end.getMessage()); //输出到客户端
}
}
}
import java.util.*;public class CONN
{
public static Connection openConnection() throws Exception
{
Context initContext = new InitialContext();
Context envContext = (Context) initContext.lookup("java:/comp/env");
DataSource ds = (DataSource) envContext.lookup("jdbc/webbalance");
return ds.getConnection();
}
public static void closeConnection(Connection conn) throws Exception
{
if ( conn != null )
{
conn.close();
}
} public static int executeUpdate(String sql) throws Exception
{
int count = 0;
Connection conn = null;
Statement stmt = null;
try
{
conn = openConnection();
stmt = conn.createStatement();
count = stmt.executeUpdate(sql);
}
catch ( Exception e )
{
throw e;
}
finally
{
closeConnection(conn);
}
return count;
}
public static List executeQuery(String sql) throws Exception
{
List list = new ArrayList();
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try
{
conn = openConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
ResultSetMetaData rsmd = rs.getMetaData();
while ( rs.next() )
{
Map map = new HashMap();
for ( int i = 1; i <= rsmd.getColumnCount(); i++ )
{
map.put(rsmd.getColumnName(i), rs.getString(i));
}
list.add(map);
} }
catch ( Exception e )
{
e.printStackTrace();
}
finally
{
if ( rs != null ) rs.close();
closeConnection(conn);
}
return list;
}
}使用:
1.对于insert, update, delete语句,用
int count = CONN.executeUpdate(sql);2.对于selete语句// 使用前记得import java.util.*;List list = CONN.executeQuery(sql);// 方法一:按名字取值
for ( int i = 0; i < list.size(); i++ )
{
Map map = (HashMap)list.get(i); out.println((String)mag.get("xx"));
} // 方法二:遍历取值
for ( int i = 0; i < list.size(); i++ )
{
Map map = (HashMap)list.get(i); for (Iterator it = map.keySet().iterator(); it.hasNext();)
{
String column_name = (String)it.next();
out.println("column name = " + column_name);
out.println("column value = " + (String)map.get(column_name));
}
} p.s.
1.conn = null 和 conn.close(); 是一样的。
2.在上面的executeQuery方法中,将ResultSet中的值转储到List对象,因此对性能有影响。
因为取数据时并不一次从数据库取出,而是在rs.next()时一条一条的取的。
{
// 定义为静态变量,将一直存在,直到工作目录关闭。
private static DataSource ds = null; public static Connection openConnection() throws Exception
{
// 只需要初始化1次
if ( ds == null )
{
Context initContext = new InitialContext();
Context envContext = (Context) initContext.lookup("java:/comp/env");
DataSource ds = (DataSource) envContext.lookup("jdbc/webbalance");
} return ds.getConnection();
}