Add example for using JWT fields (#741)

examples/jwt_get_claims_example_test.go

@@ -0,0 +1,67 @@
+package examples_test
+
+import (
+ "encoding/json"
+ "fmt"
+ "time"
+
+ "github.com/lestrrat-go/jwx/v2/jwt"
+)
+
+func ExampleJWT_GetClaims() {
+ tok, err := jwt.NewBuilder().
+ IssuedAt(time.Now()).
+ Issuer(`github.com/lestrrat-go/jwx`).
+ Subject(`example`).
+ Claim(`claim1`, `value1`).
+ Claim(`claim2`, `2022-05-16T07:35:56+00:00`).
+ Build()
+ if err != nil {
+ fmt.Printf("failed to build token: %s\n", err)
+ return
+ }
+
+ // Pre-defined fields have typed accessors.
+ var _ time.Time = tok.IssuedAt()
+ var _ string = tok.Issuer()
+ var _ string = tok.Subject()
+
+ var v interface{}
+ var ok bool
+
+ // But you can also get them via the generic `.Get()` method.
+ // However, v is of type interface{}, so you might need to
+ // use a type switch to properly use its value.
+ //
+ // For the key name you could also use jwt.IssuedAtKey constant
+ v, ok = tok.Get(`iat`)
+
+ // Private claims
+ v, ok = tok.Get(`claim1`)
+ v, ok = tok.Get(`claim2`)
+
+ // However, it is possible to globally specify that a private
+ // claim should be parsed into a custom type.
+ // In the sample below `claim2` is to be an instance of time.Time
+ jwt.RegisterCustomField(`claim2`, time.Time{})
+
+ tok = jwt.New()
+ if err := json.Unmarshal([]byte(`{"claim2":"2022-05-16T07:35:56+00:00"}`), tok); err != nil {
+ fmt.Printf(`failed to parse token: %s`, err)
+ return
+ }
+ v, ok = tok.Get(`claim2`)
+ if !ok {
+ fmt.Printf(`failed to get private claim "claim2"`)
+ return
+ }
+ if _, ok := v.(time.Time); !ok {
+ fmt.Printf(`claim2 expected to be time.Time, but got %T`, v)
+ return
+ }
+
+ _ = v
+ _ = ok
+
+ // OUTPUT:
+}