URLEncode.encode(String,String) and new String(byte[],String) The difference between

The problem I have ： Export Excel Put the form in HttpServletResponse When returning from , Use URLEncode.encode(String,String) Handle file name ;
and Local export Excel Use new String(byte[],String) Process filename ; What is the difference between the two ？

URLEncode.encode(String,String)

• Parameters ： The first parameter is ： To transcode character string , The second parameter is ： want The name of the specified encoding （ The compiler will prompt you for any mistakes ）.

• String according to the specified encoding transcoding become URL code .

• URL Coding is actually ： One character ASCII The hexadecimal of the code . For any non ASCII Special characters for （ Such as Chinese characters 、&、%、 Space 、=） To deal with , With Percent sign % Add hexadecimal code Express .

• Such as ‘%’ use URL The code is expressed as ：‘%25’, Space Expressed as ：'+'（ Special symbols ）,‘%25’、‘%E6’、‘%5C’ It's all one URL Encoded characters .

@Test
void text1() {
    
    try {
    
        System.out.println(URLEncoder.encode(" ", "UTF-8")); // +
        System.out.println(URLEncoder.encode("！", "UTF-8"));// %EF%BC%81
        System.out.println(URLEncoder.encode("!", "UTF-8")); // %21
        System.out.println(URLEncoder.encode("/", "UTF-8")); // %2F
        System.out.println(URLEncoder.encode("\\", "UTF-8"));// %5C
        System.out.println(URLEncoder.encode("%", "UTF-8")); // %25
    } catch (UnsupportedEncodingException e) {
    
        e.printStackTrace();
    }
}

• For ordinary English letters, the result of transcoding is unchanged , Or the original character ; and Chinese characters stay UTF-8 The middle is Three bytes, one Chinese character To store the , After transcoding URL Coding is based on Three URL character To express .

@Test
void text2() {
    
    try {
    
        System.out.println(URLEncoder.encode(" I ", "UTF-8"));// %E6%88%91
        System.out.println(URLEncoder.encode(" yes ", "UTF-8"));// %E6%98%AF
        System.out.println(URLEncoder.encode(" in ", "UTF-8"));// %E4%B8%AD
        System.out.println(URLEncoder.encode(" countries ", "UTF-8"));// %E5%9B%BD
        System.out.println(URLEncoder.encode(" people ", "UTF-8"));// %E4%BA%BA

        System.out.println(Arrays.toString(" I ".getBytes(StandardCharsets.UTF_8)));// [-26, -120, -111]
        System.out.println(" I ".getBytes(StandardCharsets.UTF_8).length);    // 3
        System.out.println(URLEncoder.encode(" I ", "UTF-8").length());// 9
    } catch (UnsupportedEncodingException e) {
    
        e.printStackTrace();
    }
}

@Test
void text3() {
    
    String str = " I'm Chinese ！";
    String str1 = "I am Chinese！";
    String str2 = " I'm Chinese !";
    String str3 = "I am Chinese!";

    try {
    
        System.out.println(URLEncoder.encode(str, "UTF-8")); // %E6%88%91%E6%98%AF%E4%B8%AD%E5%9B%BD%E4%BA%BA%EF%BC%81
        System.out.println(URLEncoder.encode(str1, "UTF-8"));// I+am+Chinese%EF%BC%81
        System.out.println(URLEncoder.encode(str2, "UTF-8"));// %E6%88%91%E6%98%AF%E4%B8%AD%E5%9B%BD%E4%BA%BA%21
        System.out.println(URLEncoder.encode(str3, "UTF-8"));// I+am+Chinese%21
        System.out.println(new String(str.getBytes(), StandardCharsets.UTF_8)); //  I'm Chinese ！
        System.out.println(new String(str1.getBytes(), StandardCharsets.UTF_8));// I am Chinese！
        System.out.println(new String(str2.getBytes(), StandardCharsets.UTF_8));//  I'm Chinese !
        System.out.println(new String(str3.getBytes(), StandardCharsets.UTF_8));// I am Chinese!
    } catch (UnsupportedEncodingException e) {
    
        e.printStackTrace();
    }
}

new String(byte[],String)

• Parameters ： The first parameter is ： Bytecode array ; The second parameter is ： want The name of the specified encoding , Recommended StandardCharsets Class to represent , Such as StandardCharsets.UTF_8 namely "UTF-8".

@Test
void text4() {
    
    String str = " I'm Chinese ！";
    String str1 = "I am Chinese！";
    String str2 = " I'm Chinese !";
    String str3 = "I am Chinese!";

    System.out.println(new String(str.getBytes(), StandardCharsets.UTF_8)); //  I'm Chinese ！
    System.out.println(new String(str1.getBytes(), StandardCharsets.UTF_8));// I am Chinese！
    System.out.println(new String(str2.getBytes(), StandardCharsets.UTF_8));//  I'm Chinese !
    System.out.println(new String(str3.getBytes(), StandardCharsets.UTF_8));// I am Chinese!
}

• getBytes(String)： be used for Converts a string into a bytecode array according to the specified encoding , The parameter is the same as the second parameter of the method above , The name of the specified encoding , When there is no parameter , Applicable to the default character set of the platform code .

System.out.println(Arrays.toString(" I ".getBytes(StandardCharsets.UTF_8)));// [-26, -120, -111]
System.out.println(Arrays.toString(" I ".getBytes()));// [-26, -120, -111]

• Encode bytecode as specified Regenerate a string .

summary

• The results are different ：new String(byte[],String) The result is still a string ; and URLEncode.encode(String,String) The result is URL Coding string , Just to String Fashion show .

• URL code ： yes A browser used to package form input , Text format transmitted between server and browser . Commonly used to HttpServletResponse Return the filename ( You need to put HttpServletResponse As a file output stream ).

• new String(byte[],String) The method is to Change the string encoding .

• URLEncode.encode(String,String) The method is to Transcoding a string .

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