Solve the problem of Chinese garbled characters in Get request parameters

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The IDEA version used in this article is ultimate 2019.1, the JDK version is 1.8.0_141, and the Tomcat version is 9.0.12.

In the project a few days ago, when using get to send a url request to send parameters in Chinese, garbled characters appeared. After searching for the reason on the Internet, the following solutions were provided.

1.encodeURI

1.1 Front end

The front-end jsp page part of the code is as follows

<script type="text/javascript">
    function doSubmit(){
     
     
        var url = "${pageContext.request.contextPath}/test/testEncodeURI"
            + "?userName=" + encodeURI(encodeURI("张三"));
        window.location.href = url;
    }
</script>

Note

1.2 Backstage

The background test Controller is as follows

package com.example.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.servlet.http.HttpServletRequest;
import java.net.URLDecoder;

/**
 * 测试Controller
 * @author jjy
 * @date 2020-07-21
 */
@Controller
@RequestMapping("/test")
public class TestController {
    
    

    /**
     * 测试encodeURI
     * @param request
     * @return
     */
    @RequestMapping("testEncodeURI")
    public String testEncodeURI(HttpServletRequest request){
    
    
        String userName = request.getParameter("userName");
        System.out.println("Before encodeURI : " + userName);
        try {
    
    
            userName = URLDecoder.decode(userName, "UTF-8");
        } catch (Exception e){
    
    
            e.printStackTrace();
        }
        System.out.println("After encodeURI : " + userName);
        return "index";
    }
}

Note

The results are as follows

1.3 Summary

1. The encoding and decoding process is as follows:
   UTF-8 encoding->UTF-8 (iso-8859-1) encoding->iso-8859-1 decoding->UTF-8 decoding, the encoding and decoding process is symmetrical, so it will not appear Garbled.

2. The front end encodeURI twice: The
   encodeURI function uses utf-8 for encoding, and when the server is decoding, it is not decoded by uft-8 by default, so garbled characters will appear.
   EncodeURI twice, the URL obtained in the first encoding is UTF-8, and the URL obtained in the second encoding is still in UTF-8, but in effect, it is equivalent to performing UTF-8 encoding first (at this time All have been converted to ASCII characters), and the iso-8859-1 encoding is performed again, because UTF-8 encoding and ISO-8859-1 encoding have the same effect for English characters.

3. Background decoding:
   When receiving parameters in the background, first automatically decode the first time through request.getParameter() (it may be gb2312, gbk, utf-8, iso-8859-1 and other character sets, which has no effect on the result) to obtain ascii characters , And then use UTF-8 for the second decoding, usually using java.net.URLDecoder("","UTF-8") method.