README
¶
go-http/v3/rewrite
Go package for creating net/http middleware handlers to alter the contents of other (net/http) handlers.
Example
Error handler omitted for brevity.
AppendResourcesHandler
Middleware handler to append custom JavaScript and CSS tags or data attributes to the HTML output of a previous handler.
package main
import (
"io"
"log"
"net/http"
"testing"
)
func baseAppendHandler() http.Handler {
fn := func(rsp http.ResponseWriter, req *http.Request) {
rsp.Header().Set("Content-type", "text/html")
rsp.Write([]byte(`<html><head><title>Test</title></head><body>Hello world</body><html>`))
}
h := http.HandlerFunc(fn)
return h
}
func main() {
append_opts := &AppendResourcesOptions{
JavaScript: []string{"test.js"},
Stylesheets: []string{"test.css"},
DataAttributes: map[string]string{"example": "example"},
}
append_handler := baseAppendHandler()
append_handler = AppendResourcesHandler(append_handler, append_opts)
s := &http.Server{
Addr: ":8080",
Handler: append_handler,
}
defer s.Close()
go s.ListenAndServe()
rsp, _ := http.Get("http://localhost:8080")
defer rsp.Body.Close()
body, _ := io.ReadAll(rsp.Body)
fmt.Println(string(body))
// Prints:
// <html><head><title>Test</title><script type="text/javascript" src="test.js"></script><link type="text/css" rel="stylesheet" href="test.css"/></head><body data-example="example">Hello world</body></html>
}
RewriteHTMLHandler
Middleware handler to rewrite the HTML output of a previous handler.
package main
import (
"golang.org/x/net/html"
"io"
"log"
"net/http"
"testing"
)
func baseRewriteHandler() http.Handler {
fn := func(rsp http.ResponseWriter, req *http.Request) {
rsp.Header().Set("Content-type", "text/html")
rsp.Write([]byte(`<html><head><title>Test</title></head><body><p>hello world</p></body></html>`))
}
h := http.HandlerFunc(fn)
return h
}
func main() {
var rewrite_func RewriteHTMLFunc
rewrite_func = func(n *html.Node, wr io.Writer) {
if n.Type == html.ElementNode && n.Data == "p" {
n.FirstChild.Data = "HELLO WORLD"
}
for c := n.FirstChild; c != nil; c = c.NextSibling {
rewrite_func(c, wr)
}
}
rewrite_handler := baseRewriteHandler()
rewrite_handler = RewriteHTMLHandler(rewrite_handler, rewrite_func)
s := &http.Server{
Addr: ":9434",
Handler: rewrite_handler,
}
defer s.Close()
go s.ListenAndServe()
rsp, _ := http.Get("http://localhost:9434")
defer rsp.Body.Close()
body, _ := io.ReadAll(rsp.Body)
log.Println(string(body))
// Prints
// <html><head><title>Test</title></head><body><p>HELLO WORLD</p></body></html>
}
RewriteRequestHandler
Middleware handler to modify the http.Request instance passed to another handler before invoking it.
package main
import (
"fmt"
"io"
"log"
"net/http"
"testing"
)
func baseRequestHandler() http.Handler {
fn := func(rsp http.ResponseWriter, req *http.Request) {
msg := req.Header.Get("X-Message")
// See the way there is no input validation on msg? Don't do this in production...
body := fmt.Sprintf("<html><head><title>Test</title></head><body><p>%s</p></body></html>", msg)
rsp.Header().Set("Content-type", "text/html")
rsp.Write([]byte(body))
}
h := http.HandlerFunc(fn)
return h
}
func TestRewriteRequestHandler(t *testing.T) {
rewrite_func := func(req *http.Request) (*http.Request, error) {
req.Header.Set("X-Message", "hello world")
return req, nil
}
request_handler := baseRequestHandler()
request_handler = RewriteRequestHandler(request_handler, rewrite_func)
s := &http.Server{
Addr: ":9664",
Handler: request_handler,
}
defer s.Close()
go s.ListenAndServe()
rsp, _ := http.Get("http://localhost:9664")
defer rsp.Body.Close()
body, _ := io.ReadAll(rsp.Body)
log.Println(string(body))
// Prints:
// <html><head><title>Test</title></head><body><p>hello world</p></body></html>
}
Documentation
¶
Index ¶
- func AppendResourcesHandler(previous_handler http.Handler, opts *AppendResourcesOptions) http.Handler
- func RewriteHTMLHandler(previous_handler go_http.Handler, rewrite_func RewriteHTMLFunc) go_http.Handler
- func RewriteRequestHandler(next go_http.Handler, rewrite_func RewriteRequestFunc) go_http.Handler
- type AppendResourcesOptions
- type RewriteHTMLFunc
- type RewriteRequestFunc
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func AppendResourcesHandler ¶
func AppendResourcesHandler(previous_handler http.Handler, opts *AppendResourcesOptions) http.Handler
AppendResourcesHandler() creates a `RewriteHTMLFunc` callback function, configured by 'opts', and uses that callback function and 'previous_handler' to invoke the `RewriteHTMLHandler` function. All of this will cause the output of 'previous_handler' to be rewritten to append headers and data attributes defined in 'opts'.
func RewriteHTMLHandler ¶
func RewriteHTMLHandler(previous_handler go_http.Handler, rewrite_func RewriteHTMLFunc) go_http.Handler
RewriteHTMLHandler return a `net/http` middleware handle to alter the body of 'previous_handler' using 'rewrite_func'. Content is only altered if and when the "Content-Type" header (returned by 'previous_handler') is "text/html". If not the unaltered body is returned as-is.
func RewriteRequestHandler ¶
func RewriteRequestHandler(next go_http.Handler, rewrite_func RewriteRequestFunc) go_http.Handler
RewriteRequestHandler() creates a `net/http` middleware handler that invokes 'rewrite_func' with the current request to create a new or updated `http.Request` instance used to serve 'next'.
Types ¶
type AppendResourcesOptions ¶
type AppendResourcesOptions struct {
// A list of JavaScript URIs to append to an HTML document's `<head>` element as `<script>` tags.
JavaScript []string
// A list of CSS URIs to append to an HTML document's `<head>` element as `<link rel="stylesheet">` tags.
Stylesheets []string
// A dictionary of key and value pairs to append to an HTML document's <body> element as `data-{KEY}="{VALUE}` attributes.
DataAttributes map[string]string
// AppendJavaScriptAtEOF is a boolean flag to append JavaScript markup at the end of an HTML document
// rather than in the <head> HTML element. Default is false
AppendJavaScriptAtEOF bool
}
AppendResourcesOptions is a struct containing configuration options for the `AppendResourcesHandler` method.
type RewriteHTMLFunc ¶
RewriteHTMLFunc is custom callback function for altering the HTML content of 'node'
Source Files