SpringMVC-解决中文乱码问题

一、介绍

• 服务器收到请求后，将请求交给DispatcherServlet处理，这时DispatcherServlet会获取请求参数并进行封装，然后再根据请求条件找到对应的方法来处理请求。由于在进入方法前，请求参数已经被DispatcherServlet读取，所以在方法中设置编码字符集会失效。我们可以用过滤器解决中文乱码问题，SpringMVC已经实现了编码字符集的过滤器，我们只需在web.xml中配置好即可使用。
• 过滤器源码分析

    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        String encoding = this.getEncoding();
        if (encoding != null) {
        	//下面的if的this.isForceRequestEncoding()在默认情况下为false，request.getCharacterEncoding()默认情况下为true，因为Request对象没有设置编码字符集
            if (this.isForceRequestEncoding() || request.getCharacterEncoding() == null) {
                request.setCharacterEncoding(encoding);
            }
			//是否设置Response对象返回给浏览器的数据的编码字符集
            if (this.isForceResponseEncoding()) {
                response.setCharacterEncoding(encoding);
            }
        }

        filterChain.doFilter(request, response);
    }

• 项目测试
  （1）配置过滤器

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    
    <servlet>
        <servlet-name>DispatcherServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springMVC-config.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    
    <servlet-mapping>
        <servlet-name>DispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

	<!--配置过滤器-->
    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <!--设置编码字符集-->
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
        <!--设置Response对象返回给浏览器的数据采用的编码字符集为UTF-8-->
        <init-param>
            <param-name>forceResponseEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    
</web-app>

（2）控制器

@Controller
public class MyController {

    @RequestMapping(value = {"/index"})
    public String index(String username, HttpServletRequest request, HttpServletResponse response){
        String requestCharacterEncoding = request.getCharacterEncoding();
        System.out.println(requestCharacterEncoding);
        String responseCharacterEncoding = response.getCharacterEncoding();
        System.out.println(responseCharacterEncoding);
        System.out.println(username);
        return "index";
    }
}

（3）运行