Reinventing the Wheel: JSON Conversion Library (Ⅱ)

Posted on In

Building a Java library which implements JSON conversion between JSON strings and Java beans. The source code is available in here.

String => JSONElement

Briefly, the basic idea is creating sub-elements during the traversal of json string. So traversing the json string, handling the keywords, and expecting the time complexity to be O(n).

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
for (char c : json.toCharArray()) {
    switch (c) {

        case '"':
        case '\'':
            break;
        
        case '{':
            break;

        case '[':
            break;
        
        case ':':
            break;
        
        case ',':
            break;
        
        case '}':
            break;
        
        case ']':
            break;

        default:
            break;

    }
}

See StringAnalyzer for more details.

JSONElement => String

Much easier than string => JSONElement. Recursively read sub-elements and append its value to a StringBuilder.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
public static String analyze(JSONElement element) {

    StringBuilder sb = new StringBuilder();

    switch (element.getType()) {

        case LIST:
            sb.append('[');
            Iterator<JSONElement.Entry> iterator = element.iterator();
            while (iterator.hasNext()) {
                sb.append(analyze(iterator.next().getElement()));
                if (iterator.hasNext()) {
                    sb.append(',');
                }
            }
            sb.append(']');
            break;

        case MAP:
            sb.append('{');
            Iterator<JSONElement.Entry> iterator1 = element.iterator();
            while (iterator1.hasNext()) {
                JSONElement.Entry e = iterator1.next();
                sb.append('"');
                sb.append(StringUtil.escape(StringUtil.toString(e.getKey())));
                sb.append('"');
                sb.append(':');
                sb.append(analyze(e.getElement()));
                if (iterator1.hasNext()) {
                    sb.append(',');
                }
            }
            sb.append('}');
            break;

        case PRIMITIVE:
            Object v = element.asValue();
            if (v instanceof String) {
                sb.append('"');
                sb.append(StringUtil.escape((String) v));
                sb.append('"');
            } else {
                sb.append(StringUtil.toString(v));
            }
            break;

        case VOID:
            sb.append(StringUtil.NULL);
            break;

        default:
            break;

    }

    return sb.toString();

}