Spring @MatrixVariable tutorial

last modified October 18, 2023

Spring @MatrixVariable tutorial shows how to parse URL parameters with @MatrixVariable.

Spring is a popular Java application framework for creating enterprise applications.

@MatrixVariable

@MatrixVariable is used to parse name-value pairs within a path segment and bind them to method parameters. Multiple pairs are separated with semicolon. Matrix variables must be enabled first.

Spring @MatrixVariable example

The following application parses name-value pairs from the URL path segments.

pom.xml src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ ├───config │ │ │ MyWebInitializer.java │ │ │ WebConfig.java │ │ └───controller │ │ MyController.java │ ├───resources │ └───webapp │ index.html └───test └───java

This is the project structure.

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>matrixvariableex</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>17</maven.compiler.source>
    <maven.compiler.target>17</maven.compiler.target>
    <spring-version>5.3.23</spring-version>
</properties>

<dependencies>

    <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>

    </dependencies>

<build>
    <plugins>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <version>3.3.2</version>
        </plugin>

        <plugin>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-maven-plugin</artifactId>
            <version>9.4.49.v20220914</version>
        </plugin>

    </plugins>
</build>

</project>

In the pom.xml file, we have the project dependencies.

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;

@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[]{"/"};
}

}

MyWebInitializer initializes the Spring web application. It contains one configuration class: WebConfig.

com/zetcode/config/WebConfig.java

package com.zetcode.config;

import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer; import org.springframework.web.servlet.config.annotation.EnableWebMvc; import org.springframework.web.servlet.config.annotation.PathMatchConfigurer; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer; import org.springframework.web.util.UrlPathHelper;

@Configuration @EnableWebMvc @ComponentScan(basePackages = {“com.zetcode”}) public class WebConfig implements WebMvcConfigurer {

@Override
public void configurePathMatch(PathMatchConfigurer configurer) {
    var urlPathHelper = new UrlPathHelper();
    urlPathHelper.setRemoveSemicolonContent(false);
    configurer.setUrlPathHelper(urlPathHelper);
}

@Override
public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
    configurer.enable();
}

}

The WebConfig configures the Spring web application.

@Override public void configurePathMatch(PathMatchConfigurer configurer) { var urlPathHelper = new UrlPathHelper(); urlPathHelper.setRemoveSemicolonContent(false); configurer.setUrlPathHelper(urlPathHelper); }

Here we enable matrix variables.

com/zetcode/controller/MyController.java

package com.zetcode.controller;

import org.springframework.http.MediaType; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.MatrixVariable; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RestController;

import java.util.Map;

@RestController public class MyController {

@GetMapping(value = "/user/{first}/{last}",
        produces = MediaType.TEXT_PLAIN_VALUE)
public String handler1(@MatrixVariable("first") String first,
                   @MatrixVariable("last") String last) {

    return String.format("Hello %s %s", first, last);
}

@GetMapping(value = "/data/{user:.*}",
        produces = MediaType.TEXT_PLAIN_VALUE)
public String handler2(@MatrixVariable Map<String, String> data) {

    return String.format("Id: %s\nFirst name: %s\nLast Name: %s\nEmail: %s\n",
            data.get("id"), data.get("first"), data.get("last"), data.get("email"));
}

@GetMapping(value = "/geo/{continent}",
        produces = MediaType.TEXT_PLAIN_VALUE)
public String handler3(@PathVariable("continent") String continent,
                     @MatrixVariable("country") String country,
                     @MatrixVariable("capital") String capital) {

    return String.format("Continent: %s\nCountry: %s\nCapital: %s\n",
            continent, country, capital);
}

}

MyController contains mappings of request paths to handler methods.

@GetMapping(value = “/user/{first}/{last}”, produces = MediaType.TEXT_PLAIN_VALUE) public String handler1(@MatrixVariable(“first”) String first, @MatrixVariable(“last”) String last) {

return String.format("Hello %s %s", first, last);

}

Here we bind multiple matrix variables to method parameters with @MatrixVariable.

@GetMapping(value = “/data/{user:.*}”, produces = MediaType.TEXT_PLAIN_VALUE) public String handler2(@MatrixVariable Map<String, String> data) {

return String.format("Id: %s\nFirst name: %s\nLast Name: %s\nEmail: %s\n",
        data.get("id"), data.get("first"), data.get("last"), data.get("email"));

}

Here we map multiple name-value pairs into a map.

@GetMapping(value = “/geo/{continent}”, produces = MediaType.TEXT_PLAIN_VALUE) public String handler3(@PathVariable(“continent”) String continent, @MatrixVariable(“country”) String country, @MatrixVariable(“capital”) String capital) {

return String.format("Continent: %s\nCountry: %s\nCapital: %s\n",
        continent, country, capital);

}

In the third case, we combine @MatrixVariable with @PathVariable.

webapp/index.html

<!DOCTYPE html> <html lang=“en”> <head> <meta charset=“UTF-8”> <title>Home page</title> </head> <body>

<p> <a href=“http://localhost:8080/user/first=John/last=Doe”>Greet user</a> </p>

<p> <a href=“http://localhost:8080/data/id=1;first=John;last=Doe;email=johndoe@gmail.com”>Show user data</a> </p>

<p> <a href=“http://localhost:8080/geo/Europe;country=Slovakia;capital=Bratislava”>Show country info</a> </p>

</body> </html>

This is the home page. We have three links that contain name-value pairs which are parsed with @MatrixVariable annotations.

In this article we have used @MatrixVariable to parse name-value pairs on the path segments and bind them to method parameters.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

List all Spring tutorials.