Question

我正在使用java创建一个非常简单的Web服务示例。我有一个初始化为0的变量num，但我无法在结束时保留其值。根据我的数据库，它的值应该增加1。

以下是Web服务操作：

@WebMethod(operationName = "getNewID")
public String getNewID(@WebParam(name = "newID") String txt2) 
{
Connection connection = null;  
ResultSet resultSet = null;  
Statement statement = null;
int num=0;
    try 
        {  
            Class.forName("org.sqlite.JDBC");  
            connection = DriverManager.getConnection("jdbc:sqlite:src/java/db/test.sqlite");  
            statement = connection.createStatement();
            resultSet = statement.executeQuery("SELECT ID FROM LOGINDETAILS where ID = '"+txt2+"'");

            while (resultSet.next()) 
                {  
                    //System.out.println("Your ID "+ resultSet.getString("ID"));
                    num++;
                }

        } 

    catch (Exception e) 
        {  
            System.out.println("You had an exception");
            e.printStackTrace();  
        }

    finally 
        {  
        try 
            {  
                resultSet.close();  
                statement.close();  
                connection.close();  
            } 
        catch (Exception e) 
            {  
                e.printStackTrace();  
            }  
        } 
    if(num==0)
        { 
            return "Your ID does not match";
        }

    else
        {
            return "Welcome "+txt2;
        }
}

在输出中我得到了

返回方法 java.lang.String：“你的ID不匹配”

对于所有情况，只有if部分正在工作而不是其他部分。当我在类中尝试相同的方法时，它的工作正常，但不是在Web服务操作的情况下

新代码

@WebMethod(operationName = "getNewID")
public String getNewID(@WebParam(name = "newID") String txt2) 
{
String str = null;
Connection connection = null;  
ResultSet resultSet = null;  
Statement statement = null;
    int num=0;
    try 
        {  
            Class.forName("org.sqlite.JDBC");  
            connection = DriverManager.getConnection("jdbc:sqlite:src/java/db/test.sqlite");  
            statement = connection.createStatement();
            resultSet = statement.executeQuery("SELECT ID FROM LOGINDETAILS where ID = '"+txt2+"'");

            while (resultSet.next()) 
                {  
                    //System.out.println("Your ID "+ resultSet.getString("ID"));
                    num++;
                }

        } 

    catch (Exception e) 
        {  
            System.out.println("You had an exception");
            e.printStackTrace();  
        }

    finally 
        {  
        try 
            {  
                resultSet.close();  
                statement.close();  
                connection.close();  
            } 
        catch (Exception e) 
            {  
                e.printStackTrace();  
            }  
        } 
    assert num == 0 || txt2 == null : str = "num "+num+"txt2 "+txt2;
    return str;

    /*if(num==0)
        { 
            return "Your ID does not match Please Try Again Or if new user then please register";
        }

    else
        {
            return "Welcome "+txt2;
        }*/
}

在结果中我得到str的值为null。

好的我现在试过了..

@WebMethod(operationName = "getNewID")

public String getNewID(@WebParam(name = "newID") String txt2) 
{
Connection connection = null;  
ResultSet resultSet = null;  
Statement statement = null;
int num=0;
    try 
        {  
            Class.forName("org.sqlite.JDBC");  
            connection = DriverManager.getConnection("jdbc:sqlite:src/java/db/test.sqlite");  
            statement = connection.createStatement();
            resultSet = statement.executeQuery("SELECT ID FROM LOGINDETAILS where ID = '"+txt2+"'");

            while (resultSet.next()) 
                {  
                    num++;
                }
            return resultSet.toString();

        } 

    catch (Exception e) 
        {  
            System.out.println("You had an exception");
            e.printStackTrace();
            return "You had an exception";
        }


}

我正在获取输出

java.lang.String : "You had an exception"

当它在Web服务操作之外工作正常时，为什么它在这里显示异常......我该如何纠正它？

Answer 1

检查例外情况
通过调试器，断言语句或如果您确实需要System.out.println语句来调试代码。
如果能够，请先对db执行查询，看看是否得到了预期的结果。
确保正在加载的驱动程序的类正确加载。确保lib在类路径中。

关心Rentius

Web服务操作中的变量未更新

1 个答案: