java.lang.NullPointerException
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1009)
at java.lang.Float.parseFloat(Float.java:439)
at ConvertReadings.Convertd(ConvertReadings.java:39)
at UDPServer.main(UDPServer.java:73)
休眠cfg文件
<hibernate-configuration>
<session-factory>
<property name="connection.driver_class">
com.mysql.jdbc.Driver</property>
<property name="connection.url">
jdbc:mysql://localhost:1111/DB</property>
<property name="connection.username">username</property>
<property name="connection.password">password</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="connection.autoReconnect"> true</property>
<property name="connection.autoReconnectForPools">true</property>
<!-- <property name="c3p0.validate">true</property> -->
<property name="current_session_context_class">thread</property>
<property name="hibernate.format_sql">false</property>
<property name="hibernate.connection.pool_size">5</property>
<property name="hibernate.c3p0.acquire_increment">1</property>
<property name="hibernate.c3p0.idle_test_period">1000</property>
<property name="hibernate.c3p0.max_size">5</property>
<property name="hibernate.c3p0.max_statements">0</property>
<property name="hibernate.c3p0.min_size">3</property>
<property name="hibernate.c3p0.timeout">5000</property>
转换阅读代码为
public class ConvertReadings {
public String Convertd(String a, String b, String c1, String c0 ) throws Exception
{
Converter con= new Converter();
int x;
double i = Float.parseFloat(a);
if (b.equalsIgnoreCase("HUM"))
{
double c=Float.parseFloat(c1);
double d=Float.parseFloat(c0);
x=con.convert(c, d, i);
return String.valueOf(x);
}
else if (b.equalsIgnoreCase("CO"))
{
double c=Float.parseFloat(c1);;
double d=Float.parseFloat(c0);
x=con.convert(c, d, i);
return String.valueOf(x);
}
return "Invalid sensor reading";
}
}
我得到异常的代码是
import java.util.Iterator;
import org.hibernate.HibernateException;
import org.hibernate.Query;
import org.hibernate.SessionFactory;
import org.hibernate.classic.Session;
public class FetchCoeff {
public SessionFactory factory;
public String[] testing(String x, String y) { ///here x=DevID and y= sensor type
//Session session= null ;
String c[] = new String[30];
Session session = factory.openSession();
try{
String q= "SELECT d.c1, d.c0, d.DevID, d.SensorType FROM SensorReadings d WHERE d.DevID= :DevID AND d.SensorType= :SensorType";
Query query = session.createQuery(q);
query.setParameter("DevID",x);
query.setParameter("SensorType", y);
System.out.println("query executed");
for(Iterator it=query.iterate();it.hasNext();){
Object[] ob = (Object[]) it.next(); // I am Facing problem here
c[1]= (String)ob[0]; // contains coeff 1 c1
c[0]= (String)ob[1]; // contains coeff 0 c0
}
}catch(HibernateException e){
System.out.println("Hibernate exception occured");
e.printStackTrace();
}catch(Exception d){
System.out.println("exception occured");
d.printStackTrace();
}
finally
{
session.close();
}
return c;
}
}
我已经在几周前发布了它，而我从“ JB Nizet”那里得到了解决方案，但是它只解决了一部分，而现在我在下面的部分中遇到了Null指针异常
for(Iterator it=query.iterate();it.hasNext();){
Object[] ob = (Object[]) it.next();
c[1]= (String)ob[0];
c[0]= (String)ob[1];
我认为这个对象抛出了空指针异常，但我不知道如何解决。任何人都可以在这方面帮助我..在这里，我创建了查询并迭代了结果集，并将其传递给字符串数组。
最佳答案
如果我理解正确，您将多次执行上述方法，并且在进行一些调用之后，它将引发以上异常。
该问题可能是由于您在每次方法调用时都在读取Hibernate配置并创建一个带有新连接池的全新会话工厂而产生的。
以下应仅执行一次。然后应在每次方法调用时重用同一会话工厂：
Configuration cfg= new Configuration();
cfg.configure("Hibernate.cfg.xml");
SessionFactory sessionfactory = cfg.buildSessionFactory();
关于java - sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1009)处的java.lang.NullPointerException，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/11186755/