How to Get Query Parameter in Spring Boot: Simple Guide

In Spring Boot, you get query parameters by using the @RequestParam annotation in your controller method parameters. This tells Spring to extract the value from the URL query string and pass it to your method.

Syntax

The @RequestParam annotation is placed before a method parameter in a Spring controller. It binds the query parameter from the URL to that parameter.

• @RequestParam("paramName"): specifies the query parameter name.
• Method parameter type: the type you want to convert the query parameter to (e.g., String, int).
• Optional required attribute: if set to false, the parameter is optional.
• Optional defaultValue: provides a default if the query parameter is missing.

java

public String exampleMethod(@RequestParam("name") String name) {
    // use the 'name' query parameter
}

Example

This example shows a Spring Boot controller that reads a query parameter called name from the URL and returns a greeting message. If the parameter is missing, it uses a default value.

java

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class GreetingController {

    @GetMapping("/greet")
    public String greet(@RequestParam(name = "name", required = false, defaultValue = "Guest") String name) {
        return "Hello, " + name + "!";
    }
}

Output

When you visit /greet?name=Alice, the output is: Hello, Alice!
When you visit /greet without a name parameter, the output is: Hello, Guest!

Common Pitfalls

Common mistakes when getting query parameters include:

• Not specifying required = false for optional parameters, causing errors if the parameter is missing.
• Using the wrong parameter name in @RequestParam, so Spring can't find the query parameter.
• Not providing a defaultValue when the parameter is optional, which can lead to null values.

java

/* Wrong: Missing required=false for optional parameter */
@GetMapping("/test")
public String test(@RequestParam("id") String id) {
    return "ID: " + id;
}

/* Right: Mark parameter optional with default value */
@GetMapping("/test")
public String test(@RequestParam(name = "id", required = false, defaultValue = "0") String id) {
    return "ID: " + id;
}

Quick Reference

Summary tips for using @RequestParam:

• Use @RequestParam("paramName") to bind query parameters.
• Set required = false for optional parameters.
• Use defaultValue to avoid nulls.
• Match the query parameter name exactly.

Key Takeaways

Use @RequestParam to get query parameters in Spring Boot controller methods.

Set required=false and defaultValue for optional query parameters to avoid errors.

Always match the query parameter name in @RequestParam with the URL parameter.

Missing required parameters without defaults cause errors at runtime.

You can convert query parameters to common types like String, int, boolean automatically.