所有XML文本的TrimSpaces

Question

I'm retrieving an XML string from an external web service that I do not control. Some of the data contains empty spaces <data> I have leading white space</data>. How do I trim the space from each element within the XML string?

Answer 1

You can use the primitives in the encoding/xml package to modify an XML stream on the fly. In this case implementing xml.TokenReader is a simple solution:

import (
    "bytes"
    "encoding/xml"
)

type Trimmer struct {
    dec *xml.Decoder
}

func (tr Trimmer) Token() (xml.Token, error) {
    t, err := tr.dec.Token()
    if cd, ok := t.(xml.CharData); ok {
        t = xml.CharData(bytes.TrimSpace(cd))
    }
    return t, err
}

Trimmer wraps an underlying decoder and returns a modified token stream. xml.CharData represents text nodes. Whenever one is encountered, bytes.TrimSpace is called to trim leading and trailing whitespace. All other tokens are returned unmodified.

xml.NewTokenDecoder turns Trimmer back into a regular Decoder:

import (
    "encoding/xml"
    "fmt"
    "io"
    "log"
)

var r io.Reader                          // data source
raw := xml.NewDecoder(r)                 // regular decoder
dec := xml.NewTokenDecoder(Trimmer{raw}) // trimming decoder

var v MyType
err := dec.Decode(&v)