Reasons and solutions for garbled characters exported from java to excel

Wrong and correct ways to export java: (Recommendation:java video tutorial)

错误方式：
response.setHeader("Content-Disposition", "inline;filename="+ new String(fileName.getBytes(),"utf-8"));
String fileName =    aicaseNodeDeptService.getFilename(request)+".xlsx";
 
response.setCharacterEncoding("UTF-8");
response.setContentType("application/ms-excel");
正确的方式：
response.setHeader("Content-Disposition",
        "inline;filename="+
                new String(fileName.getBytes("utf-8"),"iso8859-1"));

Reason: httpheader requires that its content must be iso8859- 1 encoding, after passing these characters to the destination, the destination program uses the opposite method Strings_utf8 = newString(s_iso88591.getBytes("ISO8859-1"),"UTF-8") to get the correct Chinese characters" ", this not only ensures compliance with the agreement, but also supports the Chinese language.

In Java, String's getBytes() method is to obtain a byte array in the operating system's default encoding format. This means that under different operating systems, the returned things are different!

String.getBytes(Stringdecode) method will return the byte array representation of a certain string under the encoding according to the specified decode encoding, such as:

byte[] b_gbk = "中".getBytes("GBK");
byte[] b_utf8 = "中".getBytes("UTF-8");
byte[] b_iso88591 = "中".getBytes("ISO8859-1");

will return the byte array representation of the Chinese character "中" in GBK, UTF-8 and ISO8859-1 encoding respectively. At this time, the length of

b_gbk is 2,

## The length of #b_utf8 is 3, and the length of

b_iso88591 is 1.

Compared with getBytes, the "中" character can be restored through new String(byte[], decode).

This new String(byte[], decode) actually It uses the specified encoding decode to parse byte[] into a string.

String s_gbk = new String(b_gbk,"GBK");
String s_utf8 = new String(b_utf8,"UTF-8");
String s_iso88591 = new String(b_iso88591,"ISO8859-1");

By outputting s_gbk, s_utf8 and s_iso88591, you will find that s_gbk and s_utf8 are both "medium", and only s_iso88591 is not recognized characters (can be understood as garbled characters), why can't the word "中" be restored after using ISO8859-1 encoding and recombination? The reason is very simple, because the encoding table of ISO8859-1 encoding does not contain Chinese characters at all. Of course, it is impossible to get the correct "中" character in ISO8859-1 through "中".getBytes("ISO8859-1"); The encoded value is already there, so it is impossible to restore it through newString().

Therefore, when obtaining byte[] through the String.getBytes(Stringdecode) method, you must make sure that the code value represented by String actually exists in the decode encoding table, so that the obtained byte[] array can be restored correctly. .

Note:

Sometimes, in order to adapt Chinese characters to certain special requirements (such as httpheader requiring that its content must be iso8859-1 encoded), the Chinese characters may be encoded in byte format To encode the situation, such as:

String s_iso88591 = newString("中".getBytes("UTF-8"),"ISO8859-1"), the s_iso8859-1 string obtained in this way is actually three For characters in ISO8859-1, after passing these characters to the destination, the destination program uses the opposite method Strings_utf8 = newString(s_iso88591.getBytes("ISO8859-

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