springboot - 在servlet中映射Errors 脱离spring mvc

应用不用Spring MVC， 采用ErrorPageRegistrar 接口能直接映射errors。

1、概览

2、java代码

1）、MyAppServlet

package com.ebc.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "appServlet", urlPatterns = "/app/*")
public class MyAppServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        String requestURI = req.getRequestURI();
        if (requestURI.endsWith("test")) {
            throw new RuntimeException("test exception from " + requestURI);
        } else if (requestURI.endsWith("test2")) {
            throw new ServletException("test servlet exception");
        } else {
            resp.getWriter().println("Response from appServlet at " + requestURI);
        }
    }
}

2）、MyErrorPageRegistrar

package com.ebc.servlet;

import org.springframework.boot.web.server.ErrorPage;
import org.springframework.boot.web.server.ErrorPageRegistrar;
import org.springframework.boot.web.server.ErrorPageRegistry;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Component;

@Component
public class MyErrorPageRegistrar implements ErrorPageRegistrar {

    @Override
    public void registerErrorPages(ErrorPageRegistry registry) {
        registry.addErrorPages(
                createNotFoundErrorPage(),
                createRuntimeExceptionPage(),
                createOtherErrorPage());
    }

    private ErrorPage createNotFoundErrorPage() {
        return new ErrorPage(HttpStatus.NOT_FOUND, "/notFoundServlet");
    }

    private ErrorPage createRuntimeExceptionPage() {
        return new ErrorPage(RuntimeException.class, "/runtimeExceptionHandler");
    }

    private ErrorPage createOtherErrorPage() {
        return new ErrorPage(Throwable.class, "/WEB-INF/internal-error.jsp");
    }
}

3）、NotFoundServlet

package com.ebc.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "not-found-error-servlet", urlPatterns = "/notFoundServlet")
public class NotFoundServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        resp.setContentType("text/html");
        PrintWriter writer = resp.getWriter();
        writer.write("<h2>Page not found </h2>");
        String requestUri = (String) req.getAttribute("javax.servlet.error.request_uri");
        writer.write("request uri: " + requestUri);
        writer.write("<br>Response from " + this.getClass());
    }
}

4）、RuntimeExceptionServlet

package com.ebc.servlet;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "runtime-handler-servlet", urlPatterns = "/runtimeExceptionHandler")
public class RuntimeExceptionServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

        resp.setContentType("text/html");
        PrintWriter writer = resp.getWriter();
        writer.write("<h2>RuntimeException</h2>");

        String requestUri = (String) req.getAttribute(RequestDispatcher.ERROR_REQUEST_URI);
        writer.write("request uri: " + requestUri);
        Integer code = (Integer) req.getAttribute(RequestDispatcher.ERROR_STATUS_CODE);
        writer.write("<br>status code: " + code);
        String errorMessage = (String) req.getAttribute(RequestDispatcher.ERROR_MESSAGE);
        writer.write("<br>error message: " + errorMessage);
        writer.write("<br>Response from "+this.getClass());
    }
}

5）、MyApplication

package com.ebc;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;

@SpringBootApplication
@ServletComponentScan
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }

}

3、internal-error.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h3>Error on server side</h3>
<p>
    <%= request.getAttribute("javax.servlet.error.exception") %>
</p>
<p>From jsp page.</p>
</body>
</html>

4、pom.xml

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-jasper</artifactId>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
    </dependency>
</dependencies>

5、执行