如何在Java中进行URL解码？｜ Java Debug 笔记-一一网

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问题：如何在Java中进行URL解码

我想使用Java，把下面这串乱码

https%3A%2F%2Fmywebsite%2Fdocs%2Fenglish%2Fsite%2Fmybook.do%3Frequest_type
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解析成这种形式

https://mywebsite/docs/english/site/mybook.do&request_type
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到目前为止我是这样写的

class StringUTF 
{
    public static void main(String[] args) 
    {
        try{
            String url = 
               "https%3A%2F%2Fmywebsite%2Fdocs%2Fenglish%2Fsite%2Fmybook.do" +
               "%3Frequest_type%3D%26type%3Dprivate";

            System.out.println(url+"Hello World!------->" +
                new String(url.getBytes("UTF-8"),"ASCII"));
        }
        catch(Exception E){
        }
    }
}
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但是上面的方法不管用，%3A和%2F这样的格式是什么意思？我要如何转换它们？

回答一

这与UTF-8或ASCII等字符编码无关。你的字符串是URL编码的。这种编码与字符编码完全不同。

尝试以下操作：

try {
    String result = java.net.URLDecoder.decode(url, StandardCharsets.UTF_8.name());
} catch (UnsupportedEncodingException e) {
    // not going to happen - value came from JDK's own StandardCharsets
}
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Java 10在API中添加了对字符集的直接支持，这意味着不需要捕获UnsupportedEncodingException异常了

String result = java.net.URLDecoder.decode(url, StandardCharsets.UTF_8);
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回答二

你应该使用java.net.URI来执行此操作，因为urldecker类是解码x-www-form-urlencoded的，它是针对表单数据的。

正如URL文档所述

管理URL编码和解码的推荐方法是使用URI。并使用toURI()和URI.toURL()进行类之间的转换。

示例

String url = "https%3A%2F%2Fmywebsite%2Fdocs%2Fenglish%2Fsite%2Fmybook.do%3Frequest_type";
System.out.println(new java.net.URI(url).getPath());
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回答三

这是我写的URL解码器：

import java.io.UnsupportedEncodingException;
import java.net.URISyntaxException;

public class URLDecoding { 

    String decoded = "";

    public String decodeMethod(String url) throws UnsupportedEncodingException
    {
        decoded = java.net.URLDecoder.decode(url, "UTF-8"); 
        return  decoded;
//"You should use java.net.URI to do this, as the URLDecoder class does x-www-form-urlencoded decoding which is wrong (despite the name, it's for form data)."
    }

    public String getPathMethod(String url) throws URISyntaxException 
    {
        decoded = new java.net.URI(url).getPath();  
        return  decoded; 
    }

    public static void main(String[] args) throws UnsupportedEncodingException, URISyntaxException 
    {
        System.out.println(" Here is your Decoded url with decode method : "+ new URLDecoding().decodeMethod("https%3A%2F%2Fmywebsite%2Fdocs%2Fenglish%2Fsite%2Fmybook.do%3Frequest_type")); 
        System.out.println("Here is your Decoded url with getPath method : "+ new URLDecoding().getPathMethod("https%3A%2F%2Fmywebsite%2Fdocs%2Fenglish%2Fsite%2Fmybook.do%3Frequest")); 

    } 

}
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