原文： http://zetcode.com/spring/custom404page/

Spring 自定义 404 错误页面教程展示了如何在 Spring Web 应用中创建自定义 404 错误页面。

Spring 是用于创建企业应用的流行 Java 应用框架。

404 代码

HTTP 404 或 404 未找到是计算机网络通信中的超文本传输协议（HTTP）标准响应代码，用于指示客户端能够与给定服务器进行通信，但是服务器找不到所请求的资源。

Spring 自定义 404 错误页面示例

以下应用使用创建自定义 404 错误页面。 默认情况下，当找不到资源时，将显示 Tomcat 的 404 错误页面。

  1. src
  2. ├───main
  3. │   ├───java
  4. │   │   └───com
  5. │   │       └───zetcode
  6. │   │           ├───config
  7. │   │           │       MyWebInitializer.java
  8. │   │           │       WebConfig.java
  9. │   │           └───controller
  10. │   │                   ControllerAdvisor.java
  11. │   │                   MyController.java
  12. │   └───resources
  13. │       │   logback.xml
  14. │       └───templates
  15. │           │   index.html
  16. │           └───error
  17. │                   404.html
  18. └───test
  19.     └───java

这是项目结构。

pom.xml

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <project xmlns="http://maven.apache.org/POM/4.0.0"
  3.          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
  5.          http://maven.apache.org/xsd/maven-4.0.0.xsd">
  6.     <modelVersion>4.0.0</modelVersion>
  8.     <groupId>com.zetcode</groupId>
  9.     <artifactId>custom404page</artifactId>
  10.     <version>1.0-SNAPSHOT</version>
  11.     <packaging>war</packaging>
  13.     <properties>
  14.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  15.         <maven.compiler.source>11</maven.compiler.source>
  16.         <maven.compiler.target>11</maven.compiler.target>
  17.     </properties>
  19.     <dependencies>
  21.         <dependency>
  22.             <groupId>ch.qos.logback</groupId>
  23.             <artifactId>logback-classic</artifactId>
  24.             <version>1.2.3</version>
  25.         </dependency>
  27.         <dependency>
  28.             <groupId>javax.servlet</groupId>
  29.             <artifactId>javax.servlet-api</artifactId>
  30.             <version>4.0.1</version>
  31.             <scope>provided</scope>
  32.         </dependency>
  34.         <dependency>
  35.             <groupId>org.springframework</groupId>
  36.             <artifactId>spring-webmvc</artifactId>
  37.             <version>5.1.3.RELEASE</version>
  38.         </dependency>
  40.         <dependency>
  41.             <groupId>org.thymeleaf</groupId>
  42.             <artifactId>thymeleaf-spring5</artifactId>
  43.             <version>3.0.11.RELEASE</version>
  44.         </dependency>
  46.         <dependency>
  47.             <groupId>org.thymeleaf</groupId>
  48.             <artifactId>thymeleaf</artifactId>
  49.             <version>3.0.11.RELEASE</version>
  50.         </dependency>
  52.     </dependencies>
  54.     <build>
  55.         <plugins>
  57.             <plugin>
  58.                 <groupId>org.apache.maven.plugins</groupId>
  59.                 <artifactId>maven-war-plugin</artifactId>
  60.                 <version>3.2.2</version>
  61.             </plugin>
  63.         </plugins>
  64.     </build>
  66. </project>

在pom.xml文件中，我们具有以下依存关系：logback-classic，javax.servlet-api，spring-webmvc和thymeleaf-spring5以及thymeleaf。

resources/logback.xml

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <configuration>
  3.     <logger name="org.springframework" level="ERROR"/>
  4.     <logger name="com.zetcode" level="INFO"/>
  6.     <appender name="consoleAppender" class="ch.qos.logback.core.ConsoleAppender">
  7.         <encoder>
  8.             <Pattern>%d{HH:mm:ss.SSS} %blue(%-5level) %magenta(%logger{36}) - %msg %n
  9.             </Pattern>
  10.         </encoder>
  11.     </appender>
  13.     <root>
  14.         <level value="INFO" />
  15.         <appender-ref ref="consoleAppender" />
  16.     </root>
  17. </configuration>

这是logback.xml配置文件。

com/zetcode/config/MyWebInitializer.java

  1. package com.zetcode.config;
  3. import org.springframework.context.annotation.Configuration;
  4. import org.springframework.web.context.WebApplicationContext;
  5. import org.springframework.web.servlet.DispatcherServlet;
  6. import org.springframework.web.servlet.FrameworkServlet;
  7. import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
  9. @Configuration
  10. public class MyWebInitializer extends
  11.         AbstractAnnotationConfigDispatcherServletInitializer {
  13.     @Override
  14.     protected Class<?>[] getRootConfigClasses() {
  15.         return null;
  16.     }
  18.     @Override
  19.     protected Class<?>[] getServletConfigClasses() {
  21.         return new Class[]{WebConfig.class};
  22.     }
  24.     @Override
  25.     protected String[] getServletMappings() {
  27.         return new String[]{"/"};
  28.     }
  30.     @Override
  31.     protected FrameworkServlet createDispatcherServlet(WebApplicationContext servletAppContext) {
  32.         var dispatcher = (DispatcherServlet) super.createDispatcherServlet(servletAppContext);
  33.         dispatcher.setThrowExceptionIfNoHandlerFound(true);
  34.         return dispatcher;
  35.     }
  36. }

MyWebInitializer初始化 Spring Web 应用。 它包含一个配置类：WebConfig。

  1. @Override
  2. protected FrameworkServlet createDispatcherServlet(WebApplicationContext servletAppContext) {
  3.     var dispatcher = (DispatcherServlet) super.createDispatcherServlet(servletAppContext);
  4.     dispatcher.setThrowExceptionIfNoHandlerFound(true);
  5.     return dispatcher;
  6. }

使用setThrowExceptionIfNoHandlerFound()，我们将 Spring 配置为在找不到资源时抛出NoHandlerFoundException。 如果我们在此行中添加注释，则会显示 Web 服务器的 404 错误页面。

com/zetcode/config/WebConfig.java

  1. package com.zetcode.config;
  3. import org.springframework.beans.factory.annotation.Autowired;
  4. import org.springframework.context.ApplicationContext;
  5. import org.springframework.context.annotation.Bean;
  6. import org.springframework.context.annotation.ComponentScan;
  7. import org.springframework.context.annotation.Configuration;
  8. import org.springframework.web.servlet.ViewResolver;
  9. import org.springframework.web.servlet.config.annotation.EnableWebMvc;
  10. import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;
  11. import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
  12. import org.thymeleaf.spring5.SpringTemplateEngine;
  13. import org.thymeleaf.spring5.templateresolver.SpringResourceTemplateResolver;
  14. import org.thymeleaf.spring5.view.ThymeleafViewResolver;
  16. @Configuration
  17. @EnableWebMvc
  18. @ComponentScan(basePackages = {"com.zetcode"})
  19. public class WebConfig implements WebMvcConfigurer {
  21.     @Autowired
  22.     private ApplicationContext applicationContext;
  24.     @Bean
  25.     public SpringResourceTemplateResolver templateResolver() {
  27.         var templateResolver = new SpringResourceTemplateResolver();
  29.         templateResolver.setApplicationContext(applicationContext);
  30.         templateResolver.setPrefix("classpath:/templates/");
  31.         templateResolver.setSuffix(".html");
  33.         return templateResolver;
  34.     }
  36.     @Bean
  37.     public SpringTemplateEngine templateEngine() {
  39.         var templateEngine = new SpringTemplateEngine();
  40.         templateEngine.setTemplateResolver(templateResolver());
  41.         templateEngine.setEnableSpringELCompiler(true);
  43.         return templateEngine;
  44.     }
  46.     @Bean
  47.     public ViewResolver viewResolver() {
  49.         var resolver = new ThymeleafViewResolver();
  50.         var registry = new ViewResolverRegistry(null, applicationContext);
  52.         resolver.setTemplateEngine(templateEngine());
  53.         registry.viewResolver(resolver);
  55.         return resolver;
  56.     }
  57. }

WebConfig配置 Thymeleaf 模板引擎。 Thymeleaf 模板文件位于类路径的templates子目录中。

com/zetcode/controller/MyController.java

  1. package com.zetcode.controller;
  3. import org.springframework.http.MediaType;
  4. import org.springframework.stereotype.Controller;
  5. import org.springframework.ui.Model;
  6. import org.springframework.web.bind.annotation.GetMapping;
  8. import java.time.LocalDateTime;
  10. @Controller
  11. public class MyController {
  13.     @GetMapping(value = "/", produces = MediaType.TEXT_HTML_VALUE)
  14.     public String home(Model model) {
  16.         model.addAttribute("now", LocalDateTime.now());
  18.         return "index";
  19.     }
  20. }

MyController包含主页的一种路由。

com/zetcode/controller/ControllerAdvisor.java

  1. package com.zetcode.controller;
  3. import org.springframework.web.bind.annotation.ControllerAdvice;
  4. import org.springframework.web.bind.annotation.ExceptionHandler;
  5. import org.springframework.web.servlet.ModelAndView;
  6. import org.springframework.web.servlet.NoHandlerFoundException;
  8. @ControllerAdvice
  9. public class ControllerAdvisor {
  11.     @ExceptionHandler(NoHandlerFoundException.class)
  12.     public ModelAndView handle(Exception ex) {
  14.         var mv = new ModelAndView();
  15.         mv.addObject("message", ex.getMessage());
  16.         mv.setViewName("error/404");
  18.         return mv;
  19.     }
  20. }

ControllerAdvisor包含NoHandlerFoundException的处理器。 它显示404.html错误页面，位于resources/templates/error/404.html中。

resources/templates/error/404.html

  1. <!doctype html>
  2. <html xmlns:th="http://www.thymeleaf.org">
  3. <head>
  4.     <meta charset="UTF-8">
  5.     <meta name="viewport" content="width=device-width, initial-scale=1.0">
  6.     <title>Resource not found</title>
  7. </head>
  8. <body>
  10. <h2>404 - resource not found</h2>
  12. <p>
  13.     <span th:text="${message}" th:remove="tag"></span>
  14. </p>
  16. </body>
  17. </html>

404.html是我们的自定义 404 错误页面。

resources/templates/index.html

  1. <!DOCTYPE html>
  2. <html xmlns:th="http://www.thymeleaf.org">
  3. <head>
  4.     <meta charset="UTF-8">
  5.     <title>Home page</title>
  6. </head>
  7. <body>
  9. <p>
  10.     This is home page.
  11. </p>
  13. <p>
  14.     Today is <span th:text="${now}"></span>
  15. </p>
  16. </body>
  17. </html>

这是主页。

在本教程中，我们在 Spring 应用中创建了一个自定义 404 错误页面。

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