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Java - example HTTP Servlet (Embedded Tomcat Server run from source code)
5 points
In this article, we want to show how to run pure HTTP Servlet (Embedded Tomcat Server) in Java.
src/com/example/DemoApplication.java file:
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package com.example;2
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import java.io.File;4
import java.io.IOException;5
import java.io.PrintWriter;6
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import org.apache.catalina.Context;8
import org.apache.catalina.LifecycleException;9
import org.apache.catalina.Server;10
import org.apache.catalina.Service;11
import org.apache.catalina.connector.Connector;12
import org.apache.catalina.startup.Tomcat;13
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import jakarta.servlet.ServletException;15
import jakarta.servlet.http.HttpServlet;16
import jakarta.servlet.http.HttpServletRequest;17
import jakarta.servlet.http.HttpServletResponse;18
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public class DemoApplication {20
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public static void main(String[] args) throws LifecycleException {22
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class MyServlet extends HttpServlet {24
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protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {26
PrintWriter writer = response.getWriter();27
writer.println("<html>");28
writer.println("<title>Welcome</title>");29
writer.println("<body>Hi!</body>");30
writer.println("</html>");31
writer.flush();32
}33
}34
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Tomcat tomcat = new Tomcat();36
Connector connector = tomcat.getConnector();37
Context context = tomcat.addContext("", getAbsolutePath("."));38
connector.setPort(8080);39
tomcat.addServlet("", "MyServlet", new MyServlet());40
context.addServletMappingDecoded("/path/to/my-servlet", "MyServlet");41
tomcat.start();42
Service service = tomcat.getService();43
Server server = tomcat.getServer();44
service.addConnector(connector);45
server.await();46
}47
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private static String getAbsolutePath(String path) {49
File file = new File(path);50
return file.getAbsolutePath();51
}52
}Warning: it is important to keep operations order in presented source code when Tomcat Server is run - in other case it won't work.
pom.xml file:
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"3
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">4
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<modelVersion>4.0.0</modelVersion>6
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<groupId>com.example</groupId>8
<artifactId>demo</artifactId>9
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<name>demo</name>11
<description>Demo project for Servlet</description>12
<version>0.0.1-SNAPSHOT</version>13
<packaging>jar</packaging>14
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<properties>16
<java.version>17</java.version>17
<maven.compiler.source>${java.version}</maven.compiler.source>18
<maven.compiler.target>${java.version}</maven.compiler.target>19
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>20
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>21
</properties>22
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<dependencies>24
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<!-- #################### -->26
<!-- TOMCAT -->27
<!-- #################### -->28
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<!-- https://mvnrepository.com/artifact/jakarta.servlet/jakarta.servlet-api -->30
<dependency>31
<groupId>jakarta.servlet</groupId>32
<artifactId>jakarta.servlet-api</artifactId>33
<version>6.0.0</version>34
<scope>provided</scope>35
</dependency>36
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<!-- https://mvnrepository.com/artifact/org.apache.tomcat.embed/tomcat-embed-core -->38
<dependency>39
<groupId>org.apache.tomcat.embed</groupId>40
<artifactId>tomcat-embed-core</artifactId>41
<version>10.1.13</version>42
</dependency>43
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<!-- https://mvnrepository.com/artifact/org.apache.tomcat.embed/tomcat-embed-jasper -->45
<dependency>46
<groupId>org.apache.tomcat.embed</groupId>47
<artifactId>tomcat-embed-jasper</artifactId>48
<version>10.1.13</version>49
</dependency>50
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<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-jasper -->52
<dependency>53
<groupId>org.apache.tomcat</groupId>54
<artifactId>tomcat-jasper</artifactId>55
<version>10.1.13</version>56
</dependency>57
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<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-jasper-el -->59
<dependency>60
<groupId>org.apache.tomcat</groupId>61
<artifactId>tomcat-jasper-el</artifactId>62
<version>10.1.13</version>63
</dependency>64
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<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-jsp-api -->66
<dependency>67
<groupId>org.apache.tomcat</groupId>68
<artifactId>tomcat-jsp-api</artifactId>69
<version>10.1.13</version>70
</dependency>71
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<!-- #################### -->73
<!-- TESTING -->74
<!-- #################### -->75
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<!-- https://mvnrepository.com/artifact/junit/junit -->77
<dependency>78
<groupId>junit</groupId>79
<artifactId>junit</artifactId>80
<version>4.13.2</version>81
<scope>test</scope>82
</dependency>83
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<!-- https://mvnrepository.com/artifact/org.assertj/assertj-core -->85
<dependency>86
<groupId>org.assertj</groupId>87
<artifactId>assertj-core</artifactId>88
<version>3.6.2</version>89
<scope>test</scope>90
</dependency>91
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<!-- #################### -->93
<!-- PREPROCESSORS -->94
<!-- #################### -->95
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<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->97
<dependency>98
<groupId>org.projectlombok</groupId>99
<artifactId>lombok</artifactId>100
<version>1.18.30</version>101
<scope>provided</scope>102
</dependency>103
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</dependencies>105
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<build>107
<finalName>${project.artifactId}</finalName>108
<sourceDirectory>src</sourceDirectory>109
<testSourceDirectory>test</testSourceDirectory>110
<plugins>111
<plugin>112
<groupId>org.apache.maven.plugins</groupId>113
<artifactId>maven-compiler-plugin</artifactId>114
<version>3.7.0</version>115
<configuration>116
<annotationProcessorPaths>117
<path>118
<groupId>org.projectlombok</groupId>119
<artifactId>lombok</artifactId>120
<version>1.18.30</version>121
</path>122
</annotationProcessorPaths>123
<source>${maven.compiler.source}</source>124
<target>${maven.compiler.target}</target>125
<verbose>true</verbose>126
</configuration>127
</plugin>128
</plugins>129
</build>130
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</project>
