Java - 注册自定义URL协议处理程序 [英] Java - Registering custom URL protocol handlers

问题描述

我尝试为类路径协议注册自定义URL处理程序，如另一个主题。以下是代码：

I tried to register a custom URL handler for a classpath protocol, as described in another thread. Here is the code:

package com.mycompany;

import org.junit.Test;
import java.net.MalformedURLException;
import java.net.URL;
import com.mycompany.protocol.classpath.Handler;

public class ParserTest {
    @Test
    public void testParsing() throws MalformedURLException {      
        System.out.println(System.getProperty("java.protocol.handler.pkgs"));

        //URL url = new URL(null, "classpath://com.mycompany/hello-world.xml", new Handler(ClassLoader.getSystemClassLoader()));
        URL url = new URL("classpath://com.mycompany/hello-world.xml");
    }
}

测试用例具有以下JVM参数：

The test case has the following JVM arguments:

-Djava.protocol.handler.pkgs=com.mycompany.protocol

System.out.println 行正确输出 com.mycompany.protocol ，因此正在设置该属性。但是，看起来它没有生效，因为上面的调用会抛出一个 java.net.MalformedURLException：unknown protocol：classpath exception。

The System.out.println line properly outputs com.mycompany.protocol, so the property is being set. However, it looks like it's not being taken into effect, because the above call will throw a java.net.MalformedURLException: unknown protocol: classpath exception.

如果我在注释行中明确提供处理程序，一切都很好。但是，我宁愿不明确地提供它 - 它应该自动完成。

If I provide the handler explicitly as in the commented line, everything is fine. However, I would rather not provide it explicitly - it should be done automatically.

我做错了什么？

推荐答案

我发现了这个问题。我使用的原始类路径处理程序类有一个非默认构造函数。当然，因为它只有一个非默认的构造函数，所以处理程序无法实例化。我向所有尝试调试此问题的人道歉，我没有看到这种联系。

I have found the issue. The original classpath handler class that I used had a non-default constructor. Of course, because it had only a non-default constructor, the handler couldn't be instantiated. I apologize to everyone who have tried to debug this issue, I failed to see this connection.

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