Spring WebJars 教程展示了如何在 Spring Web 应用中使用 WebJars。
Spring 是用于创建企业应用的流行 Java 应用框架。
Webjars
WebJars 是打包到 JAR（Java 存档）文件中的客户端 Web 库（例如 jQuery 或 Semantic UI）。 WebJars 使前端库和资产的工作自动化。
Spring WebJar 示例
在以下示例中，我们使用 Semantic-UI WebJar。 语义 UI 是一种流行的 CSS 框架。
pom.xmlsrc├───main│ ├───java│ │ └───com│ │ └───zetcode│ │ ├───config│ │ │ MyWebInitializer.java│ │ │ WebConfig.java│ │ └───controller│ │ MyController.java│ └───resources│ │ logback.xml│ └───templates│ index.html└───test └───java
这是项目结构。
pom.xml
<?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>com.zetcode</groupId> <artifactId>WebJarEx</artifactId> <version>1.0-SNAPSHOT</version> <packaging>war</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> <spring-version>5.1.4.RELEASE</spring-version> <thymeleaf-version>3.0.11.RELEASE</thymeleaf-version> </properties> <dependencies> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> <version>1.2.3</version> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>4.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>{spring-version}</version> </dependency> <dependency> <groupId>org.webjars</groupId> <artifactId>Semantic-UI</artifactId> <version>2.4.1</version> </dependency> <dependency> <groupId>org.webjars</groupId> <artifactId>webjars-locator</artifactId> <version>0.34</version> </dependency> <dependency> <groupId>org.thymeleaf</groupId> <artifactId>thymeleaf-spring5</artifactId> <version>{thymeleaf-version}</version> </dependency> <dependency> <groupId>org.thymeleaf</groupId> <artifactId>thymeleaf</artifactId> <version>${thymeleaf-version}</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-war-plugin</artifactId> <version>3.2.2</version> </plugin> </plugins> </build></project>在pom.xml中，我们具有项目依赖项。
<dependency> <groupId>org.webjars</groupId> <artifactId>Semantic-UI</artifactId> <version>2.4.1</version></dependency>
我们使用语义 UI WebJar。
<dependency> <groupId>org.webjars</groupId> <artifactId>webjars-locator</artifactId> <version>0.34</version></dependency>
webjars-locator允许我们引用资产而不引用资产的版本，该版本会自动检测到。
resources/logback.xml
<?xml version="1.0" encoding="UTF-8"?><configuration> <logger name="org.springframework" level="ERROR"/> <logger name="com.zetcode" level="INFO"/> <appender name="consoleAppender" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <Pattern>%d{HH:mm:ss.SSS} %blue(%-5level) %magenta(%logger{36}) - %msg %n </Pattern> </encoder> </appender> <root> <level value="INFO" /> <appender-ref ref="consoleAppender" /> </root></configuration>这是logback.xml配置
com/zetcode/config/MyWebInitializer.java
package com.zetcode.config;import org.springframework.context.annotation.Configuration;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.servlet.DispatcherServlet;import org.springframework.web.servlet.FrameworkServlet;import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;@Configurationpublic class MyWebInitializer extends AbstractAnnotationConfigDispatcherServletInitializer { @Override protected Class<?>[] getRootConfigClasses() { return null; } @Override protected Class<?>[] getServletConfigClasses() { return new Class[]{WebConfig.class}; } @Override protected String[] getServletMappings() { return new String[]{"/"}; }}MyWebInitializer初始化 Spring Web 应用。 它包含一个配置类：WebConfig。
com/zetcode/config/WebConfig.java
package com.zetcode.config;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.ApplicationContext;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.web.servlet.ViewResolver;import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;import org.springframework.web.servlet.config.annotation.EnableWebMvc;import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;import org.thymeleaf.spring5.SpringTemplateEngine;import org.thymeleaf.spring5.templateresolver.SpringResourceTemplateResolver;import org.thymeleaf.spring5.view.ThymeleafViewResolver;@Configuration@EnableWebMvc@ComponentScan(basePackages = {"com.zetcode"})public class WebConfig implements WebMvcConfigurer { @Autowired private ApplicationContext applicationContext; @Bean public SpringResourceTemplateResolver templateResolver() { var templateResolver = new SpringResourceTemplateResolver(); templateResolver.setApplicationContext(applicationContext); templateResolver.setPrefix("classpath:templates/"); templateResolver.setSuffix(".html"); return templateResolver; } @Bean public SpringTemplateEngine templateEngine() { var templateEngine = new SpringTemplateEngine(); templateEngine.setTemplateResolver(templateResolver()); templateEngine.setEnableSpringELCompiler(true); return templateEngine; } @Bean public ViewResolver viewResolver() { var resolver = new ThymeleafViewResolver(); var registry = new ViewResolverRegistry(null, applicationContext); resolver.setTemplateEngine(templateEngine()); registry.viewResolver(resolver); return resolver; } @Override public void addResourceHandlers(ResourceHandlerRegistry registry) { registry .addResourceHandler("/webjars/**") .addResourceLocations("/webjars/").resourceChain(false); } @Override public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) { configurer.enable(); }}WebConfig配置 Thymeleaf 模板引擎，告诉 Spring 在哪里寻找 WebJars，并启用转发到默认 servlet 来处理静态资源的功能。
@Overridepublic void addResourceHandlers(ResourceHandlerRegistry registry) { registry .addResourceHandler("/webjars/**") .addResourceLocations("/webjars/").resourceChain(false);}我们将通过/webjars/路径引用 WebJars。 对于版本无关的 WebJars，必须调用resourceChain()方法。
com/zetcode/controller/MyController.java
package com.zetcode.controller;import org.springframework.stereotype.Controller;import org.springframework.ui.Model;import org.springframework.web.bind.annotation.GetMapping;import java.util.List;@Controllerpublic class MyController { @GetMapping(value = "/") public String home(Model model) { var words = List.of("wood", "star", "cloud", "water", "river", "spring"); model.addAttribute("words", words); return "index"; }} MyController包含主页的一种路由。 我们向模板发送一些数据。 数据将显示在 HTML 表中，该表将使用 Semantic-UI 设置样式。
resources/templates/index.html
<!DOCTYPE html><html xmlns:th="http://www.thymeleaf.org"><head> <meta charset="UTF-8"> <title>Home page</title> <link rel="stylesheet" th:href="@{/webjars/Semantic-UI/semantic.css}"></head><body><section class="ui container"> <h2>English words</h2> <table class="ui striped celled table"> <thead> <tr> <th>Index</th> <th>Word</th> </tr> </thead> <tbody> <tr th:each="word : {words}"> <td th:text="{wordStat.index + 1}">Index</td> <td th:text="${word}">A word</td> </tr> </tbody> </table></section></body></html>这是主页。
<link rel="stylesheet" th:href="@{/webjars/Semantic-UI/semantic.css}">我们链接到semantic.css文件，该文件来自 WebJar。
<table class="ui striped celled table">
CSS 类来自 Semantic-UI 库。
在本教程中，我们创建了一个使用 Semantic-UI WebJar 样式化 HTML 表的样式。
