java.lang.IllegalArgumentException: Illegal character in scheme at index 0

有时候，通过httplicent发送url的时候，你会遇到懊恼的java.lang.IllegalArgumentException: Illegal character in scheme at index 0。

你会看到  空格被转成了+号了。 
When to encode space to plus (+) or %20 ...

google 上有解释：

    

URLEncoder not able to translate space character

52 down vote favorite 8

I am expecting System.out.println(java.net.URLEncoder.encode("Hello World", "UTF-8")); to output: Hello%20World (20 is ASCII Hex code for space) However, what I get is: Hello+World Am I using the wrong method? What is the correct method I should be using?

This behaves as expected. The

URLEncoder

implements the HTML Specifications for how to encode URLs in HTML forms.

From the
javadocs:

This class contains static methods for converting a String to the application/x-www-form-urlencoded MIME format.

and from the
HTML Specification:

application/x-www-form-urlencoded

Forms submitted with this content type must be encoded as follows:

Control names and values are escaped. Space characters are replaced by `+'

You will have to replace it, e.g.:

System.out.println(java.net.URLEncoder.encode("Hello World", "UTF-8").replace("+", "%20"));

https://www.gotosearch.info/?gws_rd=cr#safe=strict&q=why+urlencoder+change+the+space+to+a+%2B
作为程序员。你做好用google，百度的话，估计找半天找不到一个好答案，google，一般答案就在那里了。