Handling Invalid Requests with ResponseEntity

Introduction

Welcome to this lesson! Previously, you've focused on handling standard scenarios when building REST APIs with Spring Boot. Now, you'll delve into how to manage situations where users make invalid requests, such as trying to access resources that do not exist. To achieve this, you'll utilize ResponseEntity in Spring Boot . This allows you to return meaningful HTTP status codes, which indicate the success or failure of the operations, making your APIs more reliable and user-friendly.

HTTP Status Codes Overview

To begin, familiarize yourself with HTTP status codes . When a server responds to a request, it includes a status code that indicates the outcome. A status code is a 3-digit number, such as 200 or 404 . HTTP status codes are categorized into five groups: 1xx (Informational): Request received; continuing process. 2xx (Successful): The request was successfully received, understood, and accepted. 3xx (Redirection): Further action needs to be taken to complete the request. 4xx (Client Error): The request contains bad syntax or cannot be fulfilled. 5xx (Server Error): The server failed to fulfill an apparently valid request.

Common HTTP Status Codes

Next, focus on the most commonly used status codes that you’ll be dealing with in this lesson: Status Code Description 200 OK - The request has succeeded. 201 Created - The request has been fulfilled, resulting in the creation of a new resource. 204 No Content - The server successfully processed the request but is not returning any content. 400 Bad Request - The server could not understand the request due to invalid syntax. 401 Unauthorized - The client must authenticate itself to get the requested response. 404 Not Found - The server cannot find the requested resource. 500 Internal Server Error - The server has encountered a situation it doesn't know how to handle.

Status Code	Description
`200`	OK - The request has succeeded.
`201`	Created - The request has been fulfilled, resulting in the creation of a new resource.
`204`	No Content - The server successfully processed the request but is not returning any content.
`400`	Bad Request - The server could not understand the request due to invalid syntax.
`401`	Unauthorized - The client must authenticate itself to get the requested response.
`404`	Not Found - The server cannot find the requested resource.
`500`	Internal Server Error - The server has encountered a situation it doesn't know how to handle.

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Kotlin

@GetMapping("/recipes/{id}")
fun getRecipeById(@PathVariable id: UUID): ResponseEntity<RecipeItem> {
    val recipe = recipeRepository.findById(id)
    return if (recipe == null) {
        ResponseEntity(HttpStatus.NOT_FOUND) // Returns 404 Not Found if the item doesn't exist.
    } else {
        ResponseEntity(recipe, HttpStatus.OK) // Returns 200 OK if the item exists.
    }
}

@GetMapping("/recipes/{id}")
fun getRecipeById(@PathVariable id: UUID): ResponseEntity<RecipeItem> {
    val recipe = recipeRepository.findById(id)
    return if (recipe == null) {
        ResponseEntity(HttpStatus.NOT_FOUND) // Returns 404 Not Found if the item doesn't exist.
    } else {
        ResponseEntity(recipe, HttpStatus.OK) // Returns 200 OK if the item exists.
    }
}

Kotlin

@GetMapping("/recipes/{id}")
fun getRecipeById(@PathVariable id: UUID): ResponseEntity<RecipeItem> {
    val recipe = recipeRepository.findById(id)
    return if (recipe == null) {
        ResponseEntity.status(HttpStatus.NOT_FOUND).build() // Returns 404 Not Found if the item doesn't exist.
    } else {
        ResponseEntity.ok(recipe) // Returns 200 OK if the item exists.
    }
}

@GetMapping("/recipes/{id}")
fun getRecipeById(@PathVariable id: UUID): ResponseEntity<RecipeItem> {
    val recipe = recipeRepository.findById(id)
    return if (recipe == null) {
        ResponseEntity.status(HttpStatus.NOT_FOUND).build() // Returns 404 Not Found if the item doesn't exist.
    } else {
        ResponseEntity.ok(recipe) // Returns 200 OK if the item exists.
    }
}

Kotlin

@GetMapping("/recipes/{id}")
fun getRecipeById(@PathVariable id: UUID): ResponseEntity<RecipeItem> {
    val recipe = recipeRepository.findById(id)
    return if (recipe == null) {
        ResponseEntity(HttpStatus.NOT_FOUND) // Returns 404 Not Found if the item doesn't exist.
    } else {
        ResponseEntity(recipe, HttpStatus.OK) // Returns 200 OK if the item exists.
    }
}

Kotlin

@GetMapping("/recipes/{id}")
fun getRecipeById(@PathVariable id: UUID): ResponseEntity<RecipeItem> {
    val recipe = recipeRepository.findById(id)
    return if (recipe == null) {
        ResponseEntity.status(HttpStatus.NOT_FOUND).build() // Returns 404 Not Found if the item doesn't exist.
    } else {
        ResponseEntity.ok(recipe) // Returns 200 OK if the item exists.
    }
}

Introduction

HTTP Status Codes Overview

Common HTTP Status Codes

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Understanding ResponseEntity

ResponseEntity in Action

ResponseEntity Methods

Using the ResponseEntity Builder Pattern

Other ResponseEntity Methods

Summary