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Java解决前端数据处理及乱码问题

作者:奔走的王木木Sir

大伙们有没有遇到数据乱码的问题,真的是让人心情烦躁,今天就来教下大家数据怎么传输到前端以及乱码问题怎么解决的,需要的朋友可以参考一下

一、数据处理

1. 处理提交数据

1.提交的名称和方法的参数名一致

//localhost:8080/user/t1?name=xxx;
@GetMapping("/t1")
public String test1(String name, Model model){
    //1.接收前端参数
    System.out.println("接收到前端的参数为:" + name);
    //2.将返回的结果传递给前端
    model.addAttribute("msg", name);
    //3.跳转视图
    return "test";
}

2.提交的名称和方法的参数名不一致

//加上@RequestParam("username")就知道是从前端接收过来localhost:8080/user/t1?username=xxx;。此时必须要通过username识别
@GetMapping("/t1")
public String test1(@RequestParam("username") String name, Model model){
    //1.接收前端参数
    System.out.println("接收到前端的参数为:" + name);
    //2.将返回的结果传递给前端
    model.addAttribute("msg", name);
    //3.跳转视图
    return "test";
}

3.提交一个对象

//前端接收的是一个对象:id, name, age
//localhost:8080/user/t1?id=1&name=xxx&age=2;
/*
* 1.接收前端用户传递的参数,判断参数的名字,假设名字直接在方法上可以直接使用
* 2.假设传递的是一个对象User,匹配User对象中的字段名:如果名字一致则ok。否则匹配不到
*
* */
@GetMapping("/t2")
public String test2(User user){
    System.out.println(user);
    //3.跳转视图
    return "test";
}

使用对象,前端传递的参数名和对象名必须一致,否则为空。

2. 数据显示到前端

2.1 ModelAndView

public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
    ModelAndView modelAndView = new ModelAndView();
    modelAndView.addObject("msg","ControllerTest1");
    modelAndView.setViewName("test");
    return modelAndView;
}

2.2 Model

@RequestMapping("/t2")
public String test(Model model){
    model.addAttribute("msg", "ControllerTest2");
    return "test";
}

2.3 ModelMap

@GetMapping("/t3")
public String test3(@RequestParam("username") String name,Model map){
    map.addAttribute("name",name);
    return "test";
}

对比:

二、乱码问题

1.form表单

 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 <html>
 <head>
     <title>Title</title>
 </head>
 <body>
 <form action="/encoding/t1" method="post">
     <input type="text" name="name">
     <input type="submit">
 </form>
 </body>
 </html>

2.写一个controller

@Controller
public class EncodingController {
    @PostMapping("/encoding/t1")
    public String test(String name, Model model){
        model.addAttribute("msg",name);
        return "test";
    }
}

3.测试结果

前面弄得好好的,结果出了个这

解决办法:

看一下自己Tomcat中的是不是设置的UTF-8。在自己下载路径下-conf-server.xml

<Connector connectionTimeout="20000" port="8080" protocol="HTTP/1.1" redirectPort="8443" URLEncoding="UTF-8"/>

1)修改提交方式

把提交方式post方法改成get方法

2)Spring提供了过滤器,可以在web.xml中直接配置。(这个基本够用)

<!--2.配置 SpringMVC的乱码过滤-->
<filter>
    <filter-name>encoding</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>utf-8</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>encoding</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

3)过滤器解决(这个不行,功能不全)

package com.hxl.filter;

import javax.servlet.*;
import java.io.IOException;

public class EncodingFilter implements Filter {


    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {

    }
}

写完就要去注册(web.xml)

<filter>
    <filter-name>encoding</filter-name>
    <filter-class>com.hxl.filter.EncodingFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>encoding</filter-name>
    <url-pattern>/</url-pattern>
</filter-mapping>

4)大神自定义过滤器

package com.hxl.filter;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Map;

/**
 * 解决get和post请求 全部乱码的过滤器
 */
public class EncodingFilter implements Filter {

    @Override
    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        //处理response的字符编码
        HttpServletResponse myResponse=(HttpServletResponse) response;
        myResponse.setContentType("text/html;charset=UTF-8");

        // 转型为与协议相关对象
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        // 对request包装增强
        HttpServletRequest myrequest = new MyRequest(httpServletRequest);
        chain.doFilter(myrequest, response);
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

}

//自定义request对象,HttpServletRequest的包装类
class MyRequest extends HttpServletRequestWrapper {

    private HttpServletRequest request;
    //是否编码的标记
    private boolean hasEncode;
    //定义一个可以传入HttpServletRequest对象的构造函数,以便对其进行装饰
    public MyRequest(HttpServletRequest request) {
        super(request);// super必须写
        this.request = request;
    }

    // 对需要增强方法 进行覆盖
    @Override
    public Map getParameterMap() {
        // 先获得请求方式
        String method = request.getMethod();
        if (method.equalsIgnoreCase("post")) {
            // post请求
            try {
                // 处理post乱码
                request.setCharacterEncoding("utf-8");
                return request.getParameterMap();
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
        } else if (method.equalsIgnoreCase("get")) {
            // get请求
            Map<String, String[]> parameterMap = request.getParameterMap();
            if (!hasEncode) { // 确保get手动编码逻辑只运行一次
                for (String parameterName : parameterMap.keySet()) {
                    String[] values = parameterMap.get(parameterName);
                    if (values != null) {
                        for (int i = 0; i < values.length; i++) {
                            try {
                                // 处理get乱码
                                values[i] = new String(values[i]
                                        .getBytes("ISO-8859-1"), "utf-8");
                            } catch (UnsupportedEncodingException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
                hasEncode = true;
            }
            return parameterMap;
        }
        return super.getParameterMap();
    }

    //取一个值
    @Override
    public String getParameter(String name) {
        Map<String, String[]> parameterMap = getParameterMap();
        String[] values = parameterMap.get(name);
        if (values == null) {
            return null;
        }
        return values[0]; // 取回参数的第一个值
    }

    //取所有值
    @Override
    public String[] getParameterValues(String name) {
        Map<String, String[]> parameterMap = getParameterMap();
        String[] values = parameterMap.get(name);
        return values;
    }
}

同样需要在web.xml中进行配置 

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