自定义Spring Boot内置Tomcat的404页面

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spring boot 的相关 404 页面配置都是针对项目路径下的（如果配置了 context-path）

在 context-path 不为空的情况下，如果访问路径不带 context-path，这时候会显示空白页面或者是 tomcat 默认 404 页面

这时候如何自定义内置 tomcat 的 404 页面呢？

查看 tomcat 错误页面的实现源码 org.apache.catalina.valves.ErrorReportValue：

report 方法中先查找是否注册了错误页面，默认情况未注册任何错误页面，然后通过 sendErrorPage 方法发送错误页面

private boolean sendErrorPage(String location, Response response) {
File file = new File(location);
if (!file.isAbsolute()) {
file = new File(getContainer().getCatalinaBase(), location);
}
if (!file.isFile() || !file.canRead()) {
getContainer().getLogger().warn(
sm.getString(“errorReportValve.errorPageNotFound”, location));
return false;
}
// Hard coded for now. Consider making this optional. At Valve level or
// page level?
response.setContentType(“text/html”);
response.setCharacterEncoding(“UTF-8”);
try (OutputStream os = response.getOutputStream();
InputStream is = new FileInputStream(file);){
IOTools.flow(is, os);
} catch (IOException e) {
getContainer().getLogger().warn(
sm.getString(“errorReportValve.errorPageIOException”, location), e);
return false;
}
return true;
}

由于 spring boot 默认打成的 jar 包运行 tomcat，所以必须要把 404 页面放到外部，这里先将 404.html 放到 resource 目录下，然后启动过程中将页面复制到 tomcat 临时目录，将 404 路径指向该页面就可以了。

这里有两种实现办法：

1、通过 AOP 修改默认注册的 ErrorReportValue

import Java.io.File;
import java.io.IOException;
import javax.servlet.Servlet;
import org.apache.catalina.startup.Tomcat;
import org.apache.catalina.valves.ErrorReportValve;
import org.apache.coyote.UpgradeProtocol;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.web.embedded.TomcatWebServerFactoryCustomizer;
import org.springframework.boot.web.embedded.tomcat.ConfigurableTomcatWebServerFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.stereotype.Component;
import org.springframework.util.FileCopyUtils;
import com.bc.core.util.FileUtil;
@Aspect
@ConditionalOnClass({Servlet.class, Tomcat.class, UpgradeProtocol.class, TomcatWebServerFactoryCustomizer.class})
@Component
public class TomcatCustomizerAspect {
@Pointcut(“execution(public void org.springframework.boot.autoconfigure.web.embedded.TomcatWebServerFactoryCustomizer.customize(*))”)
public void customize() {
}
@After(value = “customize()”)
public void doAfter(JoinPoint joinPoint) throws Throwable {
if (!(joinPoint.getArgs()[0] instanceof ConfigurableTomcatWebServerFactory)) {
return;
}
ConfigurableTomcatWebServerFactory factory = (ConfigurableTomcatWebServerFactory) joinPoint.getArgs()[0];
addTomcat404CodePage(factory);
}
private static void addTomcat404CodePage(ConfigurableTomcatWebServerFactory factory) {
factory.addContextCustomizers((context) -> {
String path = context.getCatalinaBase().getPath() + “/404.html”;
ClassPathResource cr = new ClassPathResource(“404.html”);
if (cr.exists()) {
File file404 = new File(path);
if (!file404.exists()) {
try {
FileCopyUtils.copy(cr.getInputStream(), FileUtil.openOutputStream(file404));
} catch (IOException e) {
e.printStackTrace();
}
}
}
ErrorReportValve valve = new ErrorReportValve();
valve.setProperty(“errorCode.404”, path);
valve.setShowServerInfo(false);
valve.setShowReport(false);
valve.setAsyncSupported(true);
context.getParent().getPipeline().addValve(valve);
});
}
}

2、通过自定义 BeanPostProcessor 添加自定义的 ErrorReportValve

import java.io.File;
import java.io.IOException;
import javax.servlet.Servlet;
import org.apache.catalina.startup.Tomcat;
import org.apache.catalina.valves.ErrorReportValve;
import org.apache.coyote.UpgradeProtocol;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.web.embedded.TomcatWebServerFactoryCustomizer;
import org.springframework.boot.web.embedded.tomcat.ConfigurableTomcatWebServerFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.stereotype.Component;
import org.springframework.util.FileCopyUtils;
import com.bc.core.util.FileUtil;
import lombok.extern.slf4j.Slf4j;
@ConditionalOnClass({Servlet.class, Tomcat.class, UpgradeProtocol.class, TomcatWebServerFactoryCustomizer.class})
@Component
@Slf4j
public class TomcatCustomizerBeanPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (bean instanceof ConfigurableTomcatWebServerFactory) {
ConfigurableTomcatWebServerFactory configurableTomcatWebServerFactory = (ConfigurableTomcatWebServerFactory) bean;

addTomcat404CodePage(configurableTomcatWebServerFactory);
}
return BeanPostProcessor.super.postProcessAfterInitialization(bean, beanName);
}
private static void addTomcat404CodePage(ConfigurableTomcatWebServerFactory factory) {
factory.addContextCustomizers((context) -> {
String tomcatTempPath = context.getCatalinaBase().getPath();
log.info(“tomcat 目录：{}”, tomcatTempPath);
String path = tomcatTempPath + “/404.html”;
ClassPathResource cr = new ClassPathResource(“404.html”);
if (cr.exists()) {
File file404 = new File(path);
if (!file404.exists()) {
try {
FileCopyUtils.copy(cr.getInputStream(), FileUtil.openOutputStream(file404));
} catch (IOException e) {
e.printStackTrace();
}
}
}
ErrorReportValve valve = new ErrorReportValve();
valve.setProperty(“errorCode.404”, path);
valve.setShowServerInfo(false);
valve.setShowReport(false);
valve.setAsyncSupported(true);
context.getParent().getPipeline().addValve(valve);
});
}
}