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Serving static content in Spring Boot

Spring Boot static content shows how to serve static content in a Spring Boot application.

Spring is a popular Java application framework. Spring Boot is an effort to create stand-alone, production-grade Spring based applications with minimal effort.

Spring Boot automatically adds static web resources located within any of the following directories:

The directories are located in the classpath or in the root of the ServletContext.

In our application, we have one HTML file which contains a simple link. The link triggers a response from the web Boot application. It returns a plain text message.

pom.xml
src
├───main
│   ├───java
│   │   └───com
│   │       └───zetcode
│   │           │   Application.java
│   │           ├───controller
│   │           │       MyController.java
│   │           └───model
│   │                   Message.java
│   └───resources
│       │   application.properties
│       └───static
│           │   index.html
│           └───css
│                   main.css
└───test
    └───java
        └───com
            └───zetcode
                └───controller
                        MyControllerTest.java

This is the project structure of the Spring Boot application.

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>springbootstaticex</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

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

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

This is the Maven build file. The spring-boot-starter-web is starter for building web applications using Spring MVC. The spring-boot-starter-test imports necessary testing modules. The application is packaged into a JAR file.

com/zetcode/model/Message.java
package com.zetcode.model;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class Message {

    @Value("${app.message}")
    private String message;

    public String get() {
        return message;
    }
}

Message sets up the Spring Boot application.

@Value("${app.message}")
private String message;

We inject a value from the application.properties into the message variable.

resources/application.properties
app.message=Hello there

The application.properties file contains various configuration settings of a Spring Boot application. We define a custom property having a text message.

com/zetcode/controller/MyController.java
package com.zetcode.controller;

import com.zetcode.model.Message;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class MyController {

    @Autowired
    private Message message;

    @GetMapping(path = "/message")
    @ResponseBody
    public String message() {

        return message.get();
    }
}

This is the controller class for the Spring Boot web application. A controller is decorated with the @Controller annotation. The controller has one mapping; it is mapped to the /message path and returns a plain text message.

@Autowired
private Message message;

A Message object is injected into the property.

@GetMapping(path = "/message")
@ResponseBody
public String message() {

    return message.get();
}

The message() method responds to a GET request. The @ResponseBody annotation puts the string value to the web response body.

resources/static/index.html
<!DOCTYPE html>
<html>
<head>
    <title>Home page</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link href="css/main.css" rel="stylesheet" type="text/css">
</head>
<body>

<h2>Home page</h2>

<a href="/message">Get message</a>
</body>
</html>

In the index.html file we have a link that invokes a response from the web application. The file is located in the src/main/resources/static directory, which is a default directory where Spring looks for static content.

<link href="css/main.css" rel="stylesheet" type="text/css">

In the link tag we refer to the main.css static resource, which is located in the src/main/resources/static/css directory.

resources/static/css/main.css
h2 { color: blue }

In the main.css file, we set the h2 tag to blue colour.

com/zetcode/controller/MyControllerTest.java
package com.zetcode.controller;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.servlet.MockMvc;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.forwardedUrl;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import org.springframework.web.context.WebApplicationContext;

@RunWith(SpringRunner.class)
@SpringBootTest
public class MyControllerTest {

    @Autowired
    private WebApplicationContext wac;

    private MockMvc mockMvc;

    @Before
    public void setup() {
        this.mockMvc = MockMvcBuilders.webAppContextSetup(this.wac).build();
    }

    @Test
    public void getHome() throws Exception {
        this.mockMvc.perform(get("/"))
                .andDo(print())
                .andExpect(status().isOk())
                .andExpect(forwardedUrl("index.html"));
    }

    @Test
    public void getMessage() throws Exception {
        this.mockMvc.perform(get("/message"))
                .andDo(print())
                .andExpect(status().isOk())
                .andExpect(content().string("Hello there"));
    }
}

In the MyControllerTest we have two tests: one for the home page and one for the returned message text.

com/zetcode/Application.java
package com.zetcode;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

The Application sets up the Spring Boot application. The @SpringBootApplication annotation enables auto-configuration and component scanning.

In this tutorial, we have served static context in a Spring Boot application. You might also be interested in the related tutorials: Spring Boot DataSourceBuilder tutorial, Spring Boot iText tutorial, Spring Boot RESTFul application, Introduction to Spring web applications, Standalone Spring applications, Java tutorial, or list all Spring Boot tutorials.