1x2j.go - Unmarshal arbitrary XML docs to map[string]interface{} or JSON and extract values (using wildcards, if necessary).
2
3NOTICE:
4
526mar18: This is provided to aid transitioning applications using the "x2j" package to the "mxj" package.
6
7USAGE
8
9The package is fairly well self-documented. (http://godoc.org/github.com/clbanning/x2j)
10The one really useful function is:
11
12 - Unmarshal(doc []byte, v interface{}) error
13 where v is a pointer to a variable of type 'map[string]interface{}', 'string', or
14 any other type supported by xml.Unmarshal().
15
16To retrieve a value for specific tag use:
17
18 - DocValue(doc, path string, attrs ...string) (interface{},error)
19 - MapValue(m map[string]interface{}, path string, attr map[string]interface{}, recast ...bool) (interface{}, error)
20
21The 'path' argument is a period-separated tag hierarchy - also known as dot-notation.
22It is the program's responsibility to cast the returned value to the proper type; possible
23types are the normal JSON unmarshaling types: string, float64, bool, []interface, map[string]interface{}.
24
25To retrieve all values associated with a tag occurring anywhere in the XML document use:
26
27 - ValuesForTag(doc, tag string) ([]interface{}, error)
28 - ValuesForKey(m map[string]interface{}, key string) []interface{}
29
30 Demos: http://play.golang.org/p/m8zP-cpk0O
31 http://play.golang.org/p/cIteTS1iSg
32 http://play.golang.org/p/vd8pMiI21b
33
34Returned values should be one of map[string]interface, []interface{}, or string.
35
36All the values assocated with a tag-path that may include one or more wildcard characters -
37'*' - can also be retrieved using:
38
39 - ValuesFromTagPath(doc, path string, getAttrs ...bool) ([]interface{}, error)
40 - ValuesFromKeyPath(map[string]interface{}, path string, getAttrs ...bool) []interface{}
41
42 Demos: http://play.golang.org/p/kUQnZ8VuhS
43 http://play.golang.org/p/l1aMHYtz7G
44
45NOTE: care should be taken when using "*" at the end of a path - i.e., "books.book.*". See
46the x2jpath_test.go case on how the wildcard returns all key values and collapses list values;
47the same message structure can load a []interface{} or a map[string]interface{} (or an interface{})
48value for a tag.
49
50See the test cases in "x2jpath_test.go" and programs in "example" subdirectory for more.
51
52XML PARSING CONVENTIONS
53
54 - Attributes are parsed to map[string]interface{} values by prefixing a hyphen, '-',
55 to the attribute label. [See https://godoc.org/github.com/clbanning/mxj#SetAttrPrefix for options.]
56 - If the element is a simple element and has attributes, the element value
57 is given the key '#text' for its map[string]interface{} representation. (See
58 the 'atomFeedString.xml' test data, below.)
59
60BULK PROCESSING OF MESSAGE FILES
61
62Sometime messages may be logged into files for transmission via FTP (e.g.) and subsequent
63processing. You can use the bulk XML message processor to convert files of XML messages into
64map[string]interface{} values with custom processing and error handler functions. See
65the notes and test code for:
66
67 - XmlMsgsFromFile(fname string, phandler func(map[string]interface{}) bool, ehandler func(error) bool,recast ...bool) error
68 [See https://godoc.org/github.com/clbanning/mxj#HandleXmlReader for general version.]
69
70IMPLEMENTATION NOTES
71
72Nothing fancy here, just brute force.
73
74 - Use xml.Decoder to parse the XML doc and build a tree.
75 - Walk the tree and load values into a map[string]interface{} variable, 'm', as
76 appropriate.
77 - Use json.Marshaler to convert 'm' to JSON.
78
79As for testing:
80
81 - Copy an XML doc into 'x2j_test.xml'.
82 - Run "go test" and you'll get a full dump.
83 ("pathTestString.xml" and "atomFeedString.xml" are test data from "read_test.go"
84 in the encoding/xml directory of the standard package library.)
85
86MOTIVATION
87
88I make extensive use of JSON for messaging and typically unmarshal the messages into
89map[string]interface{} variables. This is easily done using json.Unmarshal from the
90standard Go libraries. Unfortunately, many legacy solutions use structured
91XML messages; in those environments the applications would have to be refitted to
92interoperate with my components.
93
94The better solution is to just provide an alternative HTTP handler that receives
95XML doc messages and parses it into a map[string]interface{} variable and then reuse
96all the JSON-based code. The Go xml.Unmarshal() function does not provide the same
97option of unmarshaling XML messages into map[string]interface{} variables. So I wrote
98a couple of small functions to fill this gap.
99
100Of course, once the XML doc was unmarshal'd into a map[string]interface{} variable it
101was just a matter of calling json.Marshal() to provide it as a JSON string. Hence 'x2j'
102rather than just 'x2m'.
103
104USES
105
106 - putting a XML API on our message hub middleware (http://jsonhub.net)
107 - loading XML data into NoSQL database, such as, mongoDB
108
109
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