OS：macOS High Sierra （Version: 10.13.6）
IDEA：IntelliJ IDEA 2020.1.4 (Community Edition)
Database: MariaDB 10.1.13 (MariaDB是MySQL源代码的一个分支)
Java, Maven 和 IDEA 的安装配置过程，见 IDEA创建Maven Quickstart项目
1. 在 IDEA上创建 Maven Webapp 项目
New Project -> Project Type: Maven -> Project SDK: 1.8 -> Select maven-archtype-webapp: Next
Name: MavenWebapp
GroupId: com.example
ArtifactId: MavenWebapp
-> Finish
生成的项目目录结构
|-- src
| |-- main
| |-- webapp
| |-- WEB-INF
| | |- web.xml
| |-- index.jsp
|-- pom.xml
2. 使用 tomcat7-maven-plugin, 将 tomcat 内嵌运行
1) 修改 pom.xml：
<project ... >
<build>
<plugins>
<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<version>2.2</version>
<configuration>
<path>/</path>
<port>9090</port>
<uriEncoding>UTF-8</uriEncoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
*注： path 项目访问路径, 本例：localhost:9090, 如果配置的aa，则访问路径为localhost:9090/aa；uriEncoding 非必选项。
2) 运行
Run -> Edit configurations -> Click "+" -> Select "Maven"
Command line: clean tomcat7:run
Name: MavenWebapp [clean,tomcat7:run]
Before Launch:
Click "+", select "Launch Web Browser"
Browser: default
Url: http://localhost:9090
-> OK
Run -> Run "MavenWebapp [clean,tomcat7:run]"
* tomcat7 除了支持 run， 还可以支持如下 Goal:
help, deploy, deploy-only, redeploy, redeploy-only, undeploy,
exec-war, exec-war-only, run-war, run-war-only,
standalone-war, standalone-war-only, shutdown
3) 打包 War
Run -> Edit configurations -> Click "+" -> Select "Maven"
Command line: clean tomcat7:run-war
Name: MavenWebapp [clean,tomcat7:run-war]
Before Launch:
Click "+", select "Launch Web Browser"
Browser: default
Url: http://localhost:9090
-> OK
Run -> Run "MavenWebapp [clean,tomcat7:run-war]"
可见到 target/MavenWebapp.war
3. 导入 Servlet 依赖包
访问 http://www.mvnrepository.com/，查询 Servlet
修改 pom.xml：
<project ... >
<dependencies>
...
<!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
...
</dependencies>
</project>
在IDE中项目列表 -> 点击鼠标右键 -> Maven -> Reload Project
4. 添加基于 web.xml 的 Servlet
1） 添加 src/main/java/com/example/BaseXmlServlet.java ，如果src/main/java 目录不存在，新增该目录并把它 Mark as "Sources Root"
package com.example;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class BaseXmlServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
ServletConfig config = getServletConfig();
response.setContentType("text/html;charset=UTF-8");
PrintWriter writer = response.getWriter();
writer.write(config.getServletName() + " -> doGet()<br/>");
writer.close();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//doGet(request, response);
}
}
2) 修改 src/main/webapp/WEB-INF/web.xml
<web-app>
...
<welcome-file-list>
<welcome-file>BaseXmlServlet</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>BaseXmlServlet</servlet-name>
<servlet-class>com.example.BaseXmlServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>BaseXmlServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
...
</web-app>
3) 从 web.xml 读取 context-param参数
修改 src/main/webapp/WEB-INF/web.xml
<web-app>
...
<context-param>
<param-name>Username</param-name>
<param-value>Webapp</param-value>
</context-param>
<context-param>
<param-name>Url</param-name>
<param-value>http://www.jianshu.com</param-value>
</context-param>
...
</web-app>
添加代码到 BaseXmlServlet.java ：
import java.util.Enumeration;
import javax.servlet.ServletContext;
...
ServletContext context = request.getServletContext();
Enumeration<String> initParameterNames = context.getInitParameterNames();
while (initParameterNames.hasMoreElements()) {
String initParamName = initParameterNames.nextElement();
String initParamValue = context.getInitParameter(initParamName);
writer.write(initParamName + ": " + initParamValue + "<br/>");
}
访问 http://localhost:9090
5. 添加基于注解 @WebServlet 的 Servlet
1) 添加 src/main/java/com/example/BaseAnnotationServlet.java
package com.example;
import java.io.IOException;
//import java.io.PrintWriter;
import java.io.OutputStream;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.annotation.WebServlet;
import javax.servlet.annotation.WebInitParam;
@WebServlet(name = "BaseAnnotationServlet",
urlPatterns = {"/annotation" },
description = "des full",
loadOnStartup = 1,
asyncSupported = false,
initParams = {
@WebInitParam(name = "name1", value = "value 1", description = "des 1"),
@WebInitParam(name = "name2", value = "value 2", description = "des 2")
})
public class BaseAnnotationServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
ServletConfig config = getServletConfig();
String strOutPut = config.getServletName() + " -> doGet()<br/>";
strOutPut += "name1: " + config.getInitParameter("name1") + "<br/>";
strOutPut += "name2: " + config.getInitParameter("name2") + "<br/>";
response.setContentType("text/html;charset=UTF-8");
OutputStream os = response.getOutputStream();
os.write(strOutPut.getBytes());
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//doGet(request, response);
}
}
2) 读取资源文件
添加 src/main/resources/config.properties, 如果src/main/resources 目录不存在，新增该目录并把它 Mark as “Resources Root”，增加如下内容：
db_driverClassName=org.mariadb.jdbc.Driver
db_url=jdbc:mysql://localhost/testdb?characterEncoding=utf8
db_username=root
db_password=123456
用 Servlet 的 getClass() 导入资源文件。
添加代码到BaseAnnotationServlet.java：
import java.io.InputStream;
import java.util.Properties;
...
InputStream resStream = this.getClass().getResourceAsStream("/config.properties");
Properties properties = new Properties();
properties.load(resStream);
writer.write("Config Properties<br/>");
writer.write("db_driverClassName: " + properties.getProperty("db_driverClassName") + "<br>");
writer.write("db_url: " + properties.getProperty("db_url") + "<br>");
writer.write("db_username: " + properties.getProperty("db_username") + "<br/>");
writer.write("db_password: " + properties.getProperty("db_password") + "<br/>");
...
访问 http://localhost:9090/annotation
