Java Method類 getGenericExceptionTypes()用法及代碼示例

java.lang.reflectMethod類的getGenericExceptionTypes()方法返回一個Type對象數組，該對象表示方法對象拋出的用於處理異常的異常。使用此方法，由使用thrown子句的方法處理的所有異常均作為Type對象的數組返回。如果應用了此方法的方法在其throws子句中未聲明任何異常，則此方法返回長度為0的數組。

例：

Code:
public class demo{
    public void setValue(String value)
    throws ClassNotFoundException, ArrayIndexOutOfBoundsException, 
            ArithmeticException {}
}
Explanation:
In the above method when we going to apply getGenericExceptionTypes() method
it is going to return array of the exception types.
Array = {
          java.lang.ClassNotFoundException,
          java.lang.ArrayIndexOutOfBoundsException,
          java.lang.ArithmeticException,
        }

用法:

public Type[] getGenericExceptionTypes()

返回值：它返回此Method對象引發的異常類型的數組

異常：此方法引發以下異常：

GenericSignatureFormatError-如果通用方法簽名與JVM規範中指定的格式不同。
TypeNotPresentException-如果throws子句指定的異常類型引用了不存在的類型聲明。
MalformedParameterizedTypeException-如果底層可執行文件的throws子句引用了由於某種原因而無法實例化的參數化類型。

以下示例程序旨在說明Method類的getGenericExceptionTypes()方法：

程序1:在getGenericExceptionTypes()的幫助下打印方法拋出的所有異常類型

/* 
* Program Demonstrate how to apply  
* getGenericExceptionTypes() method 
*/
import java.lang.reflect.Method; 
import java.lang.reflect.Type; 
  
public class GFG { 
  
    // Main method 
    public static void main(String[] args) 
    { 
        try { 
            // create class object 
            Class classobj = demoClass.class; 
  
            // create parameter type of string 
            Class[] parameterTypes = { String.class }; 
  
            // get list of method objects 
            Method[] methods = classobj.getMethods(); 
  
            // loop through all methods 
            for (Method m:methods) { 
  
                if (m.getName().equals("setValue") 
                    || m.getName().equals("getValue")) { 
  
                    // apply getGenericExceptionTypes() method 
                    Type[] genericExceptions = m.getGenericExceptionTypes(); 
  
                    // print exception Types thrown by method Object 
                    System.out.println("Generic Exception Thrown by Method:"
                                       + m.getName()); 
  
                    System.out.println("Generic Exception Type Array length:"
                                       + genericExceptions.length); 
  
                    // If method has Exception then print 
                    if (genericExceptions.length > 0) { 
  
                        System.out.println("Exception class object details:"); 
  
                        for (Type type:genericExceptions) { 
  
                            System.out.println(type.getTypeName()); 
                        } 
                    } 
                    System.out.println(); 
                } 
            } 
        } 
        catch (Exception e) { 
            e.printStackTrace(); 
        } 
    } 
} 
// a simple class 
class demoClass { 
  
    String value; 
  
    // throw some exception by method 
    public void setValue(String value) 
        throws ClassNotFoundException, 
               ArrayIndexOutOfBoundsException, 
               ArithmeticException 
    { 
        this.value = value; 
    } 
  
    // method throwing no exception 
    public String getValue() 
    { 
        return this.value; 
    } 
}

輸出：

Generic Exception Thrown by Method:getValue
Generic Exception Type Array length:0

Generic Exception Thrown by Method:setValue
Generic Exception Type Array length:3
Exception class object details:
java.lang.ClassNotFoundException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArithmeticException

程序2:檢查特定的異常

/* 
* Program Demonstrate how to  
* apply getGenericExceptionTypes() method 
*/
  
import java.lang.reflect.Method; 
import java.lang.reflect.Type; 
  
public class GFG { 
  
    // a simple class 
    class GFGSampleClass { 
  
        String value; 
  
        // throw some exception by method 
        public void setValue(String value) 
            throws ClassNotFoundException, 
                   ArrayIndexOutOfBoundsException, 
                   ArithmeticException 
        { 
            this.value = value; 
        } 
    } 
  
    // Main method 
    public static void main(String[] args) 
    { 
        try { 
            // create class object 
            Class classobj = GFGSampleClass.class; 
  
            // get list of method objects 
            Method[] methods = classobj.getMethods(); 
  
            // get Method Object for setValue 
            Method method = null; 
            for (Method m:methods) { 
                if (m.getName().equals("setValue")) 
                    method = m; 
            } 
  
            // check whether method throw 
            // ArithmeticException Exception 
            Type airthmeticExClassobj = ArithmeticException.class; 
  
            boolean response = isCertainExceptionIsThrown(method, 
                                                          airthmeticExClassobj); 
            System.out.println("ArithmeticException"
                               + " is thrown by setValue():" + response); 
  
            // check whether method throw 
            // IndexOutOfBoundsException Exception 
            Type exceptionObj = IndexOutOfBoundsException.class; 
  
            response = isCertainExceptionIsThrown(method, 
                                                  exceptionObj); 
            System.out.println("IndexOutOfBoundsException"
                               + " is thrown by setValue():" + response); 
        } 
        catch (Exception e) { 
            e.printStackTrace(); 
        } 
    } 
  
    /* 
    * Return true if the given method throws the  
    * exception passed AS Parameter. 
    */
    private static boolean
    isCertainExceptionIsThrown(Method method, Type exceptionName) 
    { 
        // get all exception list using getGenericExceptionTypes() 
        Type exceptions[] = method.getGenericExceptionTypes(); 
  
        for (int i = 0; i < exceptions.length; i++) { 
            // check exception thrown or not 
            if (exceptions[i] == exceptionName) { 
                return true; 
            } 
        } 
  
        return false; 
    } 
}

輸出：

ArithmeticException is thrown by setValue():true
IndexOutOfBoundsException is thrown by setValue():false

參考：
https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Method.html#getGenericExceptionTypes-

相關用法

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