Question

我按照下面链接的页面上的步骤尝试使用嵌入式tomcat servlet创建一个非常简单的Java Web应用程序。

https://devcenter.heroku.com/articles/create-a-java-web-application-using-embedded-tomcat

Here是运行webapp后进入shell的内容。

服务器正在运行，但随后在Web浏览器中未显示任何内容。从浏览器中查看this screenshot。

Here是我的文件夹结构与maven打包后的屏幕截图。

pom / xml文件：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.heroku.sample</groupId>
  <artifactId>embeddedTomcatSample</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>
  <name>embeddedTomcatSample Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <properties>
    <tomcat.version>9.0.16</tomcat.version>
    <maven.compiler.source>1.6</maven.compiler.source>
    <maven.compiler.target>1.6</maven.compiler.target>
  </properties>
  <dependencies>
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-core</artifactId>
        <version>${tomcat.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-jasper</artifactId>
        <version>${tomcat.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat</groupId>
        <artifactId>tomcat-jasper</artifactId>
        <version>${tomcat.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat</groupId>
        <artifactId>tomcat-jasper-el</artifactId>
        <version>${tomcat.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat</groupId>
        <artifactId>tomcat-jsp-api</artifactId>
        <version>${tomcat.version}</version>
    </dependency>
  </dependencies>
  <build>
    <finalName>embeddedTomcatSample</finalName>
    <plugins>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>appassembler-maven-plugin</artifactId>
            <version>2.0.0</version>
            <configuration>
                <assembleDirectory>target</assembleDirectory>
                <programs>
                    <program>
                        <mainClass>launch.Main</mainClass>
                        <name>webapp</name>
                    </program>
                </programs>
            </configuration>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>assemble</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
  </build>
</project>

发射器类：

package launch;

import java.io.File;

import org.apache.catalina.WebResourceRoot;
import org.apache.catalina.core.StandardContext;
import org.apache.catalina.startup.Tomcat;
import org.apache.catalina.webresources.DirResourceSet;
import org.apache.catalina.webresources.StandardRoot;

public class Main {

    public static void main(String[] args) throws Exception {

        String webappDirLocation = "src/main/webapp/";
        Tomcat tomcat = new Tomcat();

        //The port that we should run on can be set into an environment variable
        //Look for that variable and default to 8080 if it isn't there.
        String webPort = System.getenv("PORT");
        if(webPort == null || webPort.isEmpty()) {
            webPort = "8080";
        }

        tomcat.setPort(Integer.valueOf(webPort));

        StandardContext ctx = (StandardContext) tomcat.addWebapp("/", new File(webappDirLocation).getAbsolutePath());
        System.out.println("configuring app with basedir: " + new File("./" + webappDirLocation).getAbsolutePath());

        // Declare an alternative location for your "WEB-INF/classes" dir
        // Servlet 3.0 annotation will work
        File additionWebInfClasses = new File("target/classes");
        WebResourceRoot resources = new StandardRoot(ctx);
        resources.addPreResources(new DirResourceSet(resources, "/WEB-INF/classes",
                additionWebInfClasses.getAbsolutePath(), "/"));
        ctx.setResources(resources);

        tomcat.start();
        tomcat.getServer().await();
    }
}

Servlet类：

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(
        name = "MyServlet",
        urlPatterns = {"/hello"}
    )
public class HelloServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        ServletOutputStream out = resp.getOutputStream();
        out.write("hello heroku".getBytes());
        out.flush();
        out.close();
    }

}

我已经在Linux和Windows上尝试过此操作。我还遵循了另外2个类似的简单指南，并遇到了相同的问题。

任何人都可以帮助我找到问题所在吗？非常感谢。

Answer 1

希望我的答案来晚了，但昨晚我显然遇到了同样的问题。我在SO上找到了答案：

您似乎尚未向嵌入式服务器添加连接器。

对于tomcat 8，这不是必需的，因此，大多数可用的示例代码都没有提到这一点。给出的解决方案对我有用。只需在tomcat.setPort调用之后添加以下行即可：

tomcat.getConnector(); // Trigger the creation of the default connector

使用嵌入式Tomcat的Java Web应用程序正在运行，但未显示在浏览器中

1 个答案: