Spring Boot serve text
last modified July 20, 2023
Spring Boot serve text tutorial shows how to serve plain text in a Spring Boot application.
Spring is a popular Java application framework and Spring Boot is an evolution of Spring that helps create stand-alone, production-grade Spring based applications easily.
Content type
Content type, or media type, is a string sent along with a file indicating the type of the file. It describes the content format; for example, an HTML file might be labeled text/html, or an image file as image/png. It serves the same purpose as filename extensions on Windows.
The content-type header values is used to indicate the
media type of the resource. The text/plain; charset=utf-8 is used
for text files.
Spring Boot serve text example
The following application shows three ways to send text to the client.
build.gradle
...
src
├── main
│ ├── java
│ │ └── com
│ │ └── zetcode
│ │ ├── Application.java
│ │ └── controller
│ │ └── MyController.java
│ └── resources
└── test
├── java
└── resources
This is the project structure.
plugins {
id 'org.springframework.boot' version '3.1.1'
id 'io.spring.dependency-management' version '1.1.0'
id 'java'
}
group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'
repositories {
mavenCentral()
}
dependencies {
implementation 'org.springframework.boot:spring-boot-starter-web'
}
This is the Gradle build file. We only need the
spring-boot-starter-web dependency.
package com.zetcode.controller;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;
@Controller
public class MyController {
@GetMapping(value = "/", produces = MediaType.TEXT_PLAIN_VALUE)
public @ResponseBody
String home() {
return "home page";
}
@GetMapping(value = "/about")
public void test(HttpServletResponse response) throws IOException {
response.addHeader("content-type", "text/plain; charset=utf-8");
response.setStatus(200);
PrintWriter out = response.getWriter();
out.println("about page");
}
@GetMapping(value = "/contact")
public ResponseEntity<String> contact() {
var httpHeaders = new HttpHeaders();
httpHeaders.setContentType(new MediaType("text", "plain", StandardCharsets.UTF_8));
return new ResponseEntity<>("contact page", httpHeaders, HttpStatus.OK);
}
}
We have three methods to return text in the controller. Each method uses a different technique.
@Controller
public class MyController {
@GetMapping(value = "/", produces = MediaType.TEXT_PLAIN_VALUE)
public @ResponseBody
String home() {
return "home page";
}
Since the controller is annotated with the @Controller annotation,
we have to add the @ResponseBody annotation to directly write
to the body of the response rather that returning a view name to be processed.
The home method has a String return type and
the produces attribute is set to MediaType.TEXT_PLAIN_VALUE.
@GetMapping(value = "/about")
public void test(HttpServletResponse response) throws IOException {
response.addHeader("content-type", "text/plain; charset=utf-8");
response.setStatus(200);
PrintWriter out = response.getWriter();
out.println("about page");
}
The second way uses the HttpServletResponse. It is a low-level
approach where we directly write to the response object.
@GetMapping(value = "/contact")
public ResponseEntity<String> contact() {
var httpHeaders = new HttpHeaders();
httpHeaders.setContentType(new MediaType("text", "plain", StandardCharsets.UTF_8));
return new ResponseEntity<>("contact page", httpHeaders, HttpStatus.OK);
}
In the third case, we use the ResponseEntity to serve text.
The media type is set in the HttpHeaders.
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);
}
}
Application is the entry point which sets up Spring Boot
application.
We run the application with ./gradlew bootRun.
$ curl localhost:8080 home page $ curl localhost:8080/about about page $ curl localhost:8080/contact contact page
This is the output for all three pages.
$ curl -i localhost:8080/contact HTTP/1.1 200 Content-Type: text/plain;charset=UTF-8 Content-Length: 12 Date: Thu, 20 Jul 2023 09:44:07 GMT contact page
With the curl's -i option we also include the headers.
In this article we have shown how to send text data to the client from a Spring Boot application.
