我遇到了一个错误。我的错误= { java.lang.NullPointerException }。我的错误解决方案是什么?我经常遇到这个错误。我想知道这个错误的原因是tomcat吗?谢谢。
其他İmages:
我的java classes1 [connDB.java]:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
import javax.faces.bean.ManagedBean;
@ManagedBean
public class connDB {
public static String baglanti = null;
public static int baglantihatasi = 0;
public static String hataack = "";
public static java.sql.ResultSet veriler = null;
public static Statement sorgu = null;
public static Connection sorgula = null;
public static Statement connect() {
try {
sorgu=MyAcDb("obsKA","xx","xx","3306","obsDB");
System.out.println("BAGLANDI");
} catch (Exception ex) {
System.out.println("BAGLANTI HATASI");
}
return sorgu;
}
public static Statement MyAcDb(String kul, String sif, String ip,String port,String database) throws ClassNotFoundException {
baglantihatasi = 0;
Statement sorgulama= null;
try{
Class.forName("com.mysql.jdbc.Driver");
Properties baglanInfo = new Properties();
baglanInfo.put("characterEncoding", "latin5");
baglanInfo.put("user", kul);
baglanInfo.put("password", sif);
baglanti = "jdbc:mysql://" + ip+":"+port + "/"+database;
sorgula = DriverManager.getConnection(baglanti, baglanInfo);
sorgulama = (Statement) sorgula.createStatement();
}catch(SQLException hata){
}
return sorgulama;
}
}
我的java classes2 [listDB.java]:
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import javax.faces.bean.ManagedBean;
@ManagedBean
public class listDB {
private Statement sorgu=null;
boolean sonuc;
private int ogrenciID;
private String ogrenciAD;
private String ogrenciSOYAD;
private String ogrenciNO;
private String ogrenciFAKULTE;
private String ogrenciBOLUM;
private String ogrenciMAIL;
public int getOgrenciID() {return ogrenciID;}
public void setOgrenciID(int ogrenciID) {this.ogrenciID = ogrenciID;}
public String getOgrenciAD() {return ogrenciAD;}
public void setOgrenciAD(String ogrenciAD) {this.ogrenciAD = ogrenciAD;}
public String getOgrenciSOYAD() {return ogrenciSOYAD;}
public void setOgrenciSOYAD(String ogrenciSOYAD) {this.ogrenciSOYAD = ogrenciSOYAD;}
public String getOgrenciNO() {return ogrenciNO;}
public void setOgrenciNO(String ogrenciNO) {this.ogrenciNO = ogrenciNO;}
public String getOgrenciFAKULTE() {return ogrenciFAKULTE;}
public void setOgrenciFAKULTE(String ogrenciFAKULTE) {this.ogrenciFAKULTE = ogrenciFAKULTE;}
public String getOgrenciBOLUM() {return ogrenciBOLUM;}
public void setOgrenciBOLUM(String ogrenciBOLUM) {this.ogrenciBOLUM = ogrenciBOLUM;}
public String getOgrenciMAIL() {return ogrenciMAIL;}
public void setOgrenciMAIL(String ogrenciMAIL) {this.ogrenciMAIL = ogrenciMAIL;}
public ArrayList listele() throws SQLException{
ArrayList list = new ArrayList();
sorgu = connDB.connect();
String sqltext= "SELECT * FROM ogrenci";
ResultSet veriler = sorgu.executeQuery(sqltext);
while (veriler.next()) {
listDB lst = new listDB();
lst.setOgrenciID(veriler.getInt("ogrencıID"));
lst.setOgrenciAD(veriler.getString("ogrenciAD"));
lst.setOgrenciSOYAD(veriler.getString("ogrenciSOYAD"));
lst.setOgrenciNO(veriler.getString("ogrenciNO"));
lst.setOgrenciFAKULTE(veriler.getString("ogrenciFAKULTE"));
lst.setOgrenciBOLUM(veriler.getString("ogrenciBOLUM"));
lst.setOgrenciMAIL(veriler.getString("ogrenciMAIL"));
list.add(lst);
}
return list;
}
}