Spring @PathVariable教程 · ZetCode 中文系列教程

# Spring `@PathVariable`教程 > 原文： [http://zetcode.com/spring/pathvariable/](http://zetcode.com/spring/pathvariable/) Spring `@PathVariable`教程显示了如何读取带有`@PathVariable`注解的 URL 模板变量。我们创建一个 Spring RESTful 应用来演示注解。 Spring 是用于创建企业应用的流行 Java 应用框架。 ## `@PathVariable` `@PathVariable`是 Spring 注解，指示方法参数应绑定到 URI 模板变量。如果方法参数为`Map<String, String>`，则将使用所有路径变量名称和值填充映射。它具有以下可选元素： * `name` - 要绑定到的路径变量的名称 * `required` - 指示路径变量是否为必需 * `value` - 名称的别名 ## Spring `@PathVariable`示例以下示例创建一个使用`@PathVariable`的 Spring Web 应用。记录变量值。 ```java pom.xml src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ ├───config │ │ │ MyWebInitializer.java │ │ │ WebConfig.java │ │ └───controller │ │ MyController.java │ └───resources │ logback.xml └───test └───java ``` 这是 Spring 应用的项目结构。 `pom.xml` ```java <?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>pathvariableex</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>5.1.3.RELEASE</spring-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>5.1.3.RELEASE</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-war-plugin</artifactId> <version>3.2.2</version> </plugin> <plugin> <groupId>org.eclipse.jetty</groupId> <artifactId>jetty-maven-plugin</artifactId> <version>9.4.14.v20181114</version> </plugin> </plugins> </build> </project> ``` 我们声明项目依赖项。 `@PathVariable`来自`spring-webmvc`封装。 `resources/logback.xml` ```java <?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> ``` `logback.xml`是 Logback 日志库的配置文件。 `com/zetcode/config/MyWebInitializer.java` ```java package com.zetcode.config; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer; @Configuration public 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[]{"/"}; } } ``` `DispatcherServlet`是 Spring Web 应用的前端控制器，已注册在`MyWebInitializer`中。 ```java @Override protected Class<?>[] getServletConfigClasses() { return new Class[]{WebConfig.class}; } ``` `getServletConfigClasses()`返回 Web 配置类。 `com/zetcode/config/WebConfig.java` ```java package com.zetcode.config; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.config.annotation.EnableWebMvc; @Configuration @EnableWebMvc @ComponentScan(basePackages = {"com.zetcode"}) public class WebConfig { } ``` `WebConfig`通过`@EnableWebMvc`启用 Spring MVC 注解，并为`com.zetcode`包配置组件扫描。 `com/zetcode/MyController.java` ```java package com.zetcode.controller; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.http.HttpStatus; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.ResponseStatus; import org.springframework.web.bind.annotation.RestController; import java.util.Map; @RestController public class MyController { private static final Logger logger = LoggerFactory.getLogger(MyController.class); @ResponseStatus(value = HttpStatus.OK) @GetMapping(value = "/user/{name}") public void process(@PathVariable String name) { logger.info("User name: {}", name); } @ResponseStatus(value = HttpStatus.OK) @GetMapping(value = "/user/{name}/{email}") public void process2(@PathVariable String name, @PathVariable String email) { logger.info("User name: {} and email: {}", name, email); } @ResponseStatus(value = HttpStatus.OK) @GetMapping(value = "/book/{author}/{title}") public void process3(@PathVariable Map<String, String> vals) { logger.info("{}: {}", vals.get("author"), vals.get("title")); } } ``` 我们为 GET 请求提供了三个映射。 ```java @ResponseStatus(value = HttpStatus.OK) @GetMapping(value = "/user/{name}") public void process(@PathVariable String name) { logger.info("User name: {}", name); } ``` 在此代码中，URI 模板变量绑定到`name`方法参数。 ```java @ResponseStatus(value = HttpStatus.OK) @GetMapping(value = "/user/{name}/{email}") public void process2(@PathVariable String name, @PathVariable String email) { logger.info("User name: {} and email: {}", name, email); } ``` 通过指定多个`@PathVariable`注解，也可以绑定多个变量。 ```java @ResponseStatus(value = HttpStatus.OK) @GetMapping(value = "/book/{author}/{title}") public void process3(@PathVariable Map<String, String> vals) { logger.info("{}: {}", vals.get("author"), vals.get("title")); } ``` 也可以使用`Map<String, String>`绑定多个变量。 ```java $ mvn jetty:run ``` 我们启动 Jetty 服务器。 ```java $ curl localhost:8080/user/Peter/peter@gmail.com/ ``` 我们用`curl`发出请求。 ```java 22:04:35.273 INFO com.zetcode.controller.MyController - User name: Peter and email: peter@gmail.com ``` 应用记录此消息。在本教程中，我们使用 Spring 框架创建了一个 RESTful Web 应用。我们已经演示了`@PathVariable`的用法。您可能也对相关教程感兴趣： [Spring `@RequestMapping`教程](/spring/requestmapping/)， [Spring `@RequestHeader`教程](/spring/requestheader/)， [Java 教程](/lang/java/)或列出[所有 Spring 教程](/all/#spring)。