What is invocationtargetexception?

The JAVA reflection mechanism is that in the running state, for any entity class, all properties and methods of this class can be known; for any object, any of its methods and properties can be called; this dynamic acquisition of information and The function of dynamically calling object methods is called the reflection mechanism of the Java language.

The Java reflection mechanism refers to the fact that in the running state of a Java program, for any class, all properties and methods of this class can be obtained; for a given An object can call any of its properties and methods. This method of dynamically obtaining the content of a class and dynamically calling objects is called reflection mechanism. (Recommended learning: Java Video Tutorial)

Java's reflection mechanism allows programmers to obtain class-related information in more diverse and flexible ways when the class is unknown. The corresponding method is a mechanism for Java to increase its flexibility and dynamics.

Invocation targetexception is a reflection exception.

Usually the InvocationTargetException thrown is NullPointerException

View the specific method of the exception:

Put the mouse in the catch Exception ex, check the specific exception information thrown in the target.

Solution:

If the exception in the target is that a certain class cannot be found, check the error returned in sql. Check whether the fields in the class are consistent with the fields in the database. If they are inconsistent, modify them. The modification method is as follows:

If any of the fields you are looking for is defined as an enumeration type, escape it. For example,

  SELECT ID, pro_OtherProductTypeID as proOtherProductTypeID, ExchangeType as exchangeType, ObjectID as objectID, name, RequireNubs as requireNubs, Repertory as repertory,
  CASE State WHEN 1 THEN 'NORMAL' WHEN 2 THEN 'RECYCLE' WHEN 127 THEN 'DELETED' END as 'State'
    from XXX

Among them, state has been defined as an enumeration in the project. You can use the case ..when ...then ...end method to escape in SQL and convert it into the corresponding value in the enumeration. Values ​​that are not in the enumeration do not need to be converted.义

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