异常抛出如何工作？

当前正在处理一个项目，这是我无法获得的内容的过分简化的视图。

    public class throwseg1
{
    void show() throws Exception
    {
        try{
            int k = 1/0;
        }catch (ArithmeticException e){
            throw e;
        }
        try {
            throw new Exception("my.own.Exception");
        }catch (Exception e){
            throw e;
        }
    }

    void show2() throws Exception // Why just Exception is necessary here, not ArithmeticException ?
    {
        show();
    }

    void show3() throws Exception  // Why just Exception is necessary here, not ArithmeticException ?
    {
        show2();
    }

    public static void main(String s[])   // Why just Exception is necessary here, not ArithmeticException ?
    {
        try {
            throwseg1 o1 = new throwseg1();
            o1.show3();

        }catch (ArithmeticException e){
            System.out.println("Caught Arithmetic ");
        }catch (Exception e){
            System.out.println("Caught");
        }
    }
}

在Jakson中，有一个ObjectMapper从ObjectMapper源文件中抛出JsonException e它。

    public String writeValueAsString(Object value)
    throws JsonProcessingException
{
    // alas, we have to pull the recycler directly here...
    SegmentedStringWriter sw = new SegmentedStringWriter(_jsonFactory._getBufferRecycler());
    try {
        _configAndWriteValue(_jsonFactory.createGenerator(sw), value);
    } catch (JsonProcessingException e) {
        throw e;
    } catch (IOException e) { // shouldn't really happen, but is declared as possibility so:
        throw JsonMappingException.fromUnexpectedIOE(e);
    }
    return sw.getAndClear();
}

每当我使用此函数时，我都必须在方法声明中抛出JsonException，如下所示

    public void publishAssetScope(String customerUuid, AssetScope assetScope)
        throws JsonProcessingException {
   //More code
    publishMessage(customerUuid, jacksonObjectMapper.writeValueAsString(assetScope));
    
}

随后谁在调用publishAssetScope，我必须在方法签名中“抛出” JsonProcessingException。

1. 为什么我必须这样做？

其次，函数链中还有其他“抛出”“ new SomeException”异常，为什么我不必在其父调用函数的方法签名中将其作为抛出添加。

希望您能理解，我知道这是一个非常令人困惑的问题，我无法正确表达自己的意思。

谢谢