Error handlers

You can define your own handlers when a specific http error code occurs. Error handlers can be registered per Party.

Error codes are the http status codes that are bigger than or equal to 400, like 404 not found and 500 internal server error.

Example code:

package main

import "github.com/kataras/iris/v12"

func main(){
    app := iris.New()
    app.RegisterView(iris.HTML("./views", ".html"))

    app.OnErrorCode(iris.StatusNotFound, notFound)
    app.OnErrorCode(iris.StatusInternalServerError, internalServerError)
    // to register a handler for all error codes:
    // app.OnAnyErrorCode(handler)

    app.Get("/", index)

    app.Listen(":8080")
}

func notFound(ctx iris.Context) {
    // when 404 then render the template
    // $views_dir/errors/404.html
    ctx.View("errors/404.html")

    // OR, if you had more paths and you want
    // to suggest relative paths to the user:
    // suggestPaths := ctx.FindClosest(3)
    // if len(suggestPaths) == 0 {
    //     ctx.WriteString("404 not found")
    //     return
    // }

    // ctx.HTML("Did you mean?<ul>")
    // for _, s := range suggestPaths {
    //     ctx.HTML(`<li><a href="%s">%s</a></li>`, s, s)
    // }
    // ctx.HTML("</ul>")
}

func internalServerError(ctx iris.Context) {
    ctx.WriteString("Oups something went wrong, try again")
}

func index(ctx iris.Context) {
    ctx.View("index.html")
}

Learn more about View.

Iris has the EnablePathIntelligence option which can be passed to app.Run/Listen method to auto-redirect a not found path to its closest match one, e.g "http://localhost:8080/contac" to "http://localhost:8080/contact". Enable it:

app.Listen(":8080", iris.WithPathIntelligence)

You can also force all paths to be lowercased by setting the ForceLowercaseRouting option:

app.Listen(":8080", iris.WithLowercaseRouting, iris.WithPathIntelligence)

The Problem type

Iris has builtin support for the Problem Details for HTTP APIs.

The Context.Problem writes a JSON or XML problem response. Behaves exactly like Context.JSON but with default ProblemOptions.JSON indent of " " and a response content type of "application/problem+json" instead.

Use the options.RenderXML and XML fields to change this behavior and send a response of content type "application/problem+xml" instead.

func newProductProblem(productName, detail string) iris.Problem {
    return iris.NewProblem().
        // The type URI, if relative it automatically convert to absolute.
        Type("/product-error"). 
        // The title, if empty then it gets it from the status code.
        Title("Product validation problem").
        // Any optional details.
        Detail(detail).
        // The status error code, required.
        Status(iris.StatusBadRequest).
        // Any custom key-value pair.
        Key("productName", productName)
        // Optional cause of the problem, chain of Problems.
        // .Cause(other iris.Problem)
}

func fireProblem(ctx iris.Context) {
    // Response like JSON but with indent of "  " and
    // content type of "application/problem+json"
    ctx.Problem(newProductProblem("product name", "problem details"), iris.ProblemOptions{
        // Optional JSON renderer settings.
        JSON: iris.JSON{
            Indent: "  ",
        },
        // OR
        // Render as XML:
        // RenderXML: true,
        // XML:       iris.XML{Indent: "  "},
        // Sets the "Retry-After" response header.
        //
        // Can accept:
        // time.Time for HTTP-Date,
        // time.Duration, int64, float64, int for seconds
        // or string for date or duration.
        // Examples:
        // time.Now().Add(5 * time.Minute),
        // 300 * time.Second,
        // "5m",
        //
        RetryAfter: 300,
        // A function that, if specified, can dynamically set
        // retry-after based on the request. Useful for ProblemOptions reusability.
        // Overrides the RetryAfter field.
        //
        // RetryAfterFunc: func(iris.Context) interface{} { [...] }
    })
}

Outputs "application/problem+json"

{
  "type": "https://host.domain/product-error",
  "status": 400,
  "title": "Product validation problem",
  "detail": "problem error details",
  "productName": "product name"
}

When RenderXML is set to true then the response will look be rendered as XML instead.

Outputs "application/problem+xml"

<Problem>
    <Type>https://host.domain/product-error</Type>
    <Status>400</Status>
    <Title>Product validation problem</Title>
    <Detail>problem error details</Detail>
    <ProductName>product name</ProductName>
</Problem>

Full example can be found at _examples/routing/http-errors.

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