Context#formParamMap() method read all the form parameters as a map.
Example
Map<String, List<String>> formParamsMap = ctx.formParamMap();
Find the below working application.
Step 1: Create new maven project ‘javalin-read-form-params-as-a-map’.
Step 2: Update pom.xml with maven dependencies.
pom.xml
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.sample.app</groupId> <artifactId>javalin-read-form-params-as-a-map</artifactId> <version>1.0.0</version> <properties> <packaging>jar</packaging> <jdk.version>17</jdk.version> <release.version>17</release.version> </properties> <dependencies> <dependency> <groupId>io.javalin</groupId> <artifactId>javalin</artifactId> <version>5.3.2</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-simple</artifactId> <version>2.0.3</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.14.0</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-core</artifactId> <version>2.14.0</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.10.1</version> <configuration> <source>17</source> <target>17</target> </configuration> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-assembly-plugin</artifactId> <version>2.6</version> <configuration> <descriptorRefs> <descriptorRef>jar-with-dependencies</descriptorRef> </descriptorRefs> <archive> <manifest> <addClasspath>true</addClasspath> <mainClass>com.sample.app.App</mainClass> </manifest> </archive> </configuration> <executions> <execution> <id>assemble-all</id> <phase>package</phase> <goals> <goal>single</goal> </goals> </execution> </executions> </plugin> </plugins> </build> </project>
Step 3: Define JsonUtil class.
JsonUtil.java
package com.sample.app.util; import java.io.IOException; import com.fasterxml.jackson.core.JsonParseException; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.JsonMappingException; import com.fasterxml.jackson.databind.ObjectMapper; public class JsonUtil { public static String marshal(Object obj) throws JsonProcessingException { ObjectMapper mapper = new ObjectMapper(); return mapper.writeValueAsString(obj); } public static <T> T unmarshal(Class<T> clazz, String json) throws JsonParseException, JsonMappingException, IOException { ObjectMapper mapper = new ObjectMapper(); return (T) mapper.readValue(json, clazz); } }
Step 4: Define main application class.
App.java
package com.sample.app; import java.util.List; import java.util.Map; import com.sample.app.util.JsonUtil; import io.javalin.Javalin; import io.javalin.http.HttpStatus; public class App { public static void main(String[] args) { Javalin javalin = Javalin.create(); javalin.get("/", (ctx) -> { ctx.result("Welcome to Javalin programming!!!!"); }); javalin.post("/form-params-demo", (ctx) -> { Map<String, List<String>> formParamsMap = ctx.formParamMap(); ctx.result(JsonUtil.marshal(formParamsMap)).status(HttpStatus.CREATED); }); javalin.start(8080); } }
Total project structure looks like below.
Build the project
Navigate to the folder, where pom.xml is located and execute the command ‘mvn package’.
Upon successful command execution, you can see a ‘javalin-read-form-params-as-a-map-1.0.0-jar-with-dependencies.jar’ file.
$ls ./target/ archive-tmp classes generated-sources generated-test-sources javalin-read-form-params-as-a-map-1.0.0-jar-with-dependencies.jar javalin-read-form-params-as-a-map-1.0.0.jar maven-archiver maven-status test-classes
Run the application
Execute below command to run the application.
java -jar ./target/javalin-read-form-params-as-a-map-1.0.0-jar-with-dependencies.jar
$java -jar ./target/javalin-read-form-params-as-a-map-1.0.0-jar-with-dependencies.jar [main] INFO io.javalin.Javalin - Starting Javalin ... [main] INFO org.eclipse.jetty.server.Server - jetty-11.0.13; built: 2022-12-07T20:47:15.149Z; git: a04bd1ccf844cf9bebc12129335d7493111cbff6; jvm 17.0.5+9-LTS-191 [main] INFO org.eclipse.jetty.server.session.DefaultSessionIdManager - Session workerName=node0 [main] INFO org.eclipse.jetty.server.handler.ContextHandler - Started i.j.j.@30ee2816{/,null,AVAILABLE} [main] INFO org.eclipse.jetty.server.AbstractConnector - Started ServerConnector@26a7b76d{HTTP/1.1, (http/1.1)}{0.0.0.0:8080} [main] INFO org.eclipse.jetty.server.Server - Started Server@1fc2b765{STARTING}[11.0.13,sto=0] @397ms [main] INFO io.javalin.Javalin - __ ___ ______ / /___ __ ______ _/ (_)___ / ____/ __ / / __ `/ | / / __ `/ / / __ \ /___ \ / /_/ / /_/ /| |/ / /_/ / / / / / / ____/ / \____/\__,_/ |___/\__,_/_/_/_/ /_/ /_____/ https://javalin.io/documentation [main] INFO io.javalin.Javalin - Listening on http://localhost:8080/ [main] INFO io.javalin.Javalin - You are running Javalin 5.3.2 (released January 22, 2023). [main] INFO io.javalin.Javalin - Javalin started in 265ms \o/
Test the api
Execute below command to test the api.
curl --location --request POST 'http://localhost:8080/form-params-demo' \ --form 'hobbies="chess"' \ --form 'hobbies="cricket"' \ --form 'name="Krishna"' \ --form 'age="34"'
$curl --location --request POST 'http://localhost:8080/form-params-demo' \
> --form 'hobbies="chess"' \
> --form 'hobbies="cricket"' \
> --form 'name="Krishna"' \
> --form 'age="34"'
{"hobbies":["chess","cricket"],"name":["Krishna"],"age":["34"]}
You can download this application from this link.
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