2024年8月27日 星期二

No XML for Java EE Spring Application

這裡來紀錄一下如何不使用 XML 配置檔改用程式的方式來設定 Java EE + Spring 的 Web Application。

首先來看一下專案的檔案結構如下圖：




因為不用 XML 了的關係，所以我們這次範例專案中不會特別放 Java EE 的 web.xml 和 Spring 的 Config XML。

pom.xml (設定了一些要用到的 Dependency) :
<?xml version="1.0" encoding="UTF-8"?>

<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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>my.test</groupId>
  <artifactId>javaee-spring-no-xml-test</artifactId>
  <version>0.1</version>
  <packaging>war</packaging>

  <name>javaee-spring-no-xml-test Maven Webapp</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
	<dependency>
	    <groupId>javax.servlet</groupId>
	    <artifactId>javax.servlet-api</artifactId>
	    <version>4.0.1</version>
	</dependency>
	
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->  
    <dependency>
    	<groupId>org.springframework</groupId>
    	<artifactId>spring-webmvc</artifactId>
    	<version>5.3.18</version>
	</dependency>
	
	<!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-jdbc</artifactId>
	    <version>5.3.18</version>
	</dependency>

  </dependencies>

  <build>
    <finalName>javaee-spring-no-xml-test</finalName>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-war-plugin</artifactId>
          <version>3.2.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>
src/main/com/config/WebInitializer.java (Java EE Web Application 的啟動設定，取代 web.xml) :
package com.config;

import javax.servlet.ServletContext;
import javax.servlet.ServletRegistration;

import org.springframework.web.WebApplicationInitializer;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.context.support.XmlWebApplicationContext;
import org.springframework.web.servlet.DispatcherServlet;

//Servlet Container (例如 Tomcat) 會在 Web 應用啟動時尋找實作 WebApplicationInitializer 的 Class 並執行 onStartup()
public class WebInitializer implements WebApplicationInitializer {
	
	@Override
	public void onStartup(ServletContext servletContext) {
		
		//可以用 AnnotationConfigWebApplicationContext 設定 Class Config
		//或是用 XmlWebApplicationContext 設定 XML Config 
		//來建立 Spring Application 上下文 (Context)
		AnnotationConfigWebApplicationContext springWebApplicationContext = new AnnotationConfigWebApplicationContext();
		springWebApplicationContext.register(SpringApplicationConfig.class); //這裡可以指定 Spring Class Config
//		XmlWebApplicationContext springWebApplicationContext = new XmlWebApplicationContext();
//		springWebApplicationContext.setConfigLocation("classpath:application-config.xml"); //這裡可以指定 Spring XML Config
		
		DispatcherServlet dispatcherServlet = new DispatcherServlet(springWebApplicationContext);
		
		ServletRegistration.Dynamic springDispatcherServlet = servletContext.addServlet("springDispatcherServlet", dispatcherServlet);
		springDispatcherServlet.setLoadOnStartup(1);
		springDispatcherServlet.addMapping("/");
		/** 上述 code 相當於 web.xml 中的以下 DispatcherServlet 設定
		 * <servlet>
				<servlet-name>springDispatcherServlet</servlet-name>
				<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
				<init-param>
					<param-name>contextConfigLocation</param-name>
					<param-value>/xx/xx/application-config.xml</param-value>
					</init-param>
				<load-on-startup>1</load-on-startup>
			</servlet>
			<servlet-mapping>
				<servlet-name>springDispatcherServlet</servlet-name> 
				<url-pattern>/</url-pattern>
			</servlet-mapping>
		 */
	}
}
src/main/com/config/SpringApplicatoinConfig.java (Spring Config 設定，取代 Spring XML Config File) :
package com.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

@EnableWebMvc
@Configuration
@ComponentScan(basePackages = "com.*")
public class SpringApplicationConfig {
	
	@Bean
	public InternalResourceViewResolver setupViewResolver() {
		InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
		viewResolver.setPrefix("/WEB-INF/view/");
		viewResolver.setSuffix(".jsp");
		
		return viewResolver;
		
		/** 上述 code 相當於 Spring Config XML 的如下 InternalResourceViewResolver 設定
		 * <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> 
		        <property name="prefix">
		            <value>/WEB-INF/view/</value>
		        </property>
		        <property name="suffix">
		            <value>.jsp</value>
		        </property>
		    </bean>
		 */
	}
}
src/main/com/controller/TestController.java (測試用的 Controller) :
package com.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class TestController {
	
	@ResponseBody
	@RequestMapping("/test")
	public String test() {
		return "HIHI";
	}
	
	@RequestMapping("/hello")
	public String hello() {
		return "hello";
	}
	
}
src/main/webapp/WEB-INF/view/hello.jsp (測試用的 JSP View) : 
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Hello</title>
</head>
<body>
Say hello!
</body>
</html>

可以自己跑一個 Tomcat 起來試，應該可以成功存取以下 url

  1. http://localhost:8080/index.jsp (直接存取 webapp 下的 JSP Resource)
  2. http://localhost:8080/hello (會觸發 TestController.hello()，Request 會導向 webapp/WEB-INF/view/hello.jsp)
  3. http://localhost:8080/test (會觸發 TestController.test())

源碼下載分享：
javaee-spring-no-xml-test.7z


參考資料：

  1.  NO XML - Spring MVC Java-based configuration in 9 steps || Spring Annotation || Part 3

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