是一个很简单的项目,就是客户端发字符给服务,服务器查询下返回,都是用Myeclipse生成的服务和客户端,使用MSSQL 加 tomcat 我一跑起来就 Caused by: java.lang.NullPointerException
服务代码这这样,客户端就一个main传一个参数输出结果,没了
package com.service;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;public class SelGrade {
private static final String SQLString = "sun.jdbc.odbc.JdbcOdbcDriver";
private static final String SQLConString = "jdbc:odbc:TestDataBase";
private Connection con = null; public SelGrade() {
try {
Class.forName(SQLString);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
con = DriverManager.getConnection(SQLConString);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} public String selGrade(String s_id) {
String result = null;
try {
Statement stme = con.createStatement(); //这里 , at com.service.SelGrade.selGrade(SelGrade.java:32)为什么呢?
ResultSet rs = stme
.executeQuery("select * from Student where s_id='" + s_id
+ "'");
while (rs.next()) {
result = rs.getString(3);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return result;
}
}
服务代码这这样,客户端就一个main传一个参数输出结果,没了
package com.service;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;public class SelGrade {
private static final String SQLString = "sun.jdbc.odbc.JdbcOdbcDriver";
private static final String SQLConString = "jdbc:odbc:TestDataBase";
private Connection con = null; public SelGrade() {
try {
Class.forName(SQLString);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
con = DriverManager.getConnection(SQLConString);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} public String selGrade(String s_id) {
String result = null;
try {
Statement stme = con.createStatement(); //这里 , at com.service.SelGrade.selGrade(SelGrade.java:32)为什么呢?
ResultSet rs = stme
.executeQuery("select * from Student where s_id='" + s_id
+ "'");
while (rs.next()) {
result = rs.getString(3);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return result;
}
}
package com.service;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;public class SelGrade {
private static final String SQLString = "sun.jdbc.odbc.JdbcOdbcDriver";
private static final String SQLConString = "jdbc:odbc:TestDataBase";
private Connection con = null;
public String selGrade(String s_id) {
String result = null;
try {
Class.forName(SQLString);
con = DriverManager.getConnection(SQLConString);
Statement stme = con.createStatement();
ResultSet rs =stme.executeQuery("select * from Student where s_id='" + s_id + "'");
while (rs.next()) {
result = rs.getString(3);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return result;
}
}
stme.close();
con.close();
user = new User();
user.setId(rs.getInt("user_id"));
user.setName(rs.getString("user_name"));
}