JavaWeb 之 Servlet中文乱码问题

出现原因

前端后端编码不一致

浏览器默认使用UTF-8码表进行编码 ，Servlet使用ISO-8859-1码表进行编码

传输和接收方编码不一致导致乱码的产生

Request乱码

Request请求分为post和get，分别有不同的解决方案

Request乱码 - POST请求

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doPost(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//给请求中的参数设置编码格式
		request.setCharacterEncoding("UTF-8");
		
		String parameter1 = request.getParameter("parameter1");
		String parameter2 = request.getParameter("parameter2");
		System.out.println(parameter1);
		System.out.println(parameter2);
}

作用：设置从 request 中取得的值,用来指定对浏览器发送来的数据进行重新编码时，使用的编码。

使用注意事项：

• 在执行 setCharacterEncoding()之前，不能执行任何 getParameter()操作
• 通过 setCharacterEncoding 设置的编码方式只对 POST 方式提交的表单有效，对 GET 方式无效

Request乱码 - GET请求(Tomcat7.X版本)

解决方案1

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doPost(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		String parameter1 = request.getParameter("parameter1");
		parameter1 = new String(parameter1.getBytes("ISO-8859-1"),"UTF-8");
		String parameter2 = request.getParameter("parameter2");
		parameter2 = new String(parameter2.getBytes("ISO-8859-1"),"UTF-8");
		
		System.out.println(parameter1);
		System.out.println(parameter2);
}

解决方案2

在Tomcat根目录/conf/server.xml中设置编码格式

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

那么在启动服务器的时候就会读取到URIEncoding的属性配置,然后再调用自己的一个setURIEncoding方法完成设置,形参的值为我们设置的UTF-8

protected String URIEncoding = null;
public void setURIEncoding(String URIEncoding) {
         this.URIEncoding = URIEncoding;
         setProperty("URIEncoding", URIEncoding);
}

Request乱码 - GET请求(Tomcat8.X版本)

Tomcat8.x的服务器在接收GET请求时,即使参数中有中文,也不会出现乱码，作者在底层设计上的一些改动

Tomcat的连接器组件(Connector) ，Connector是Tomcat中的一个重要的组件，它负责监听Tomcat收到的请求信息，并将这些请求信息传递给Servlet规范中所定义的Request，然后将转换后的请求交给Engine组件去处理，最后将Engine返回的Response返回给客户端 。源码中我们可以看到, URIEncoding的默认值为UTF-8,所以在Tomcat8.x中,即使GET请求包含了中文的数据,也不会出现乱码了

public class Connector extends LifecycleMBeanBase  {
    
    private Charset uriCharset = StandardCharsets.UTF_8;
   
    //查询Tomcat根目录/conf/catalina.properties配置文件中的属性
	public static final boolean RECYCLE_FACADES =
Boolean.parseBoolean(System.getProperty("org.apache.catalina.connector.RECYCLE_FACADES", "false"));   
    
    public Connector() {
        this(null);
    }
    
    public Connector(String protocol) {
        setProtocol(protocol);
        // Instantiate protocol handler
        ProtocolHandler p = null;
        try {
            Class<?> clazz = Class.forName(protocolHandlerClassName);
            p = (ProtocolHandler) clazz.getConstructor().newInstance();
        } catch (Exception e) {
            log.error(sm.getString(
                    "coyoteConnector.protocolHandlerInstantiationFailed"), e);
        } finally {
            this.protocolHandler = p;
        }

        if (Globals.STRICT_SERVLET_COMPLIANCE) {
            uriCharset = StandardCharsets.ISO_8859_1;
        } else {
            uriCharset = StandardCharsets.UTF_8;
        }
    }
}

Response乱码

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	doPost(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		//设置响应内容的编码格式
	response.setContentType("text/html;charset=UTF-8");
		
	response.getWriter().println("千锋吴彦祖");
}

跳转到中文页面路径乱码

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	doPost(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
	response.sendRedirect(URLEncoder.encode("详情页面.html", "UTF-8"));
}