golang中使用json

golang中使用json的一些例子

// go_json_test project main.gopackage mainimport (    "encoding/json"    "fmt")func encode_from_map_test() {    fmt.Printf("encode_from_map_test\n")    m := map[string][]string{        "level":   {"debug"},        "message": {"File not found", "Stack overflow"},    }    if data, err := json.Marshal(m); err == nil {        fmt.Printf("%s\n", data)    }}type GameInfo struct {    Game_id   int64    Game_map  string    Game_time int32}func encode_from_object_test() {    fmt.Printf("encode_from_object_test\n")    game_infos := []GameInfo{        GameInfo{1, "map1", 20},        GameInfo{2, "map2", 60},    }    if data, err := json.Marshal(game_infos); err == nil {        fmt.Printf("%s\n", data)    }}type GameInfo1 struct {    Game_id   int64  `json:"game_id"`            // Game_id解析為game_id    Game_map  string `json:"game_map,omitempty"` // GameMap解析為game_map, 忽略空置    Game_time int32    Game_name string `json:"-"` // 忽略game_name}func encode_from_object_tag_test() {    fmt.Printf("encode_from_object_tag_test\n")    game_infos := []GameInfo1{        GameInfo1{1, "map1", 20, "name1"},        GameInfo1{2, "map2", 60, "name2"},        GameInfo1{3, "", 120, "name3"},    }    if data, err := json.Marshal(game_infos); err == nil {        fmt.Printf("%s\n", data)    }}type BaseObject struct {    Field_a string    Field_b string}type DeriveObject struct {    BaseObject    Field_c string}func encode_from_object_with_anonymous_field() {    fmt.Printf("encode_from_object_with_anonymous_field\n")    object := DeriveObject{BaseObject{"a", "b"}, "c"}    if data, err := json.Marshal(object); err == nil {        fmt.Printf("%s\n", data)    }}// convert interface// 在調用Marshal(v interface{})時，該函數會判斷v是否滿足json.Marshaler或者 encoding.Marshaler 介面，// 如果滿足，則會調用這兩個介面來進行轉換（如果兩個都滿足，優先調用json.Marshaler）/*// json.Marshalertype Marshaler interface {    MarshalJSON() ([]byte, error)}// encoding.TextMarshalertype TextMarshaler interface {    MarshalText() (text []byte, err error)}*/type Point struct {    X int    Y int}func (pt Point) MarshalJSON() ([]byte, error) {    return []byte(fmt.Sprintf(`{"px" : %d, "py" : %d}`, pt.X, pt.Y)), nil}func encode_from_object_with_marshaler_interface() {    fmt.Printf("encode_from_object_with_marshaler_interface\n")    if data, err := json.Marshal(Point{50, 50}); err == nil {        fmt.Printf("%s\n", data)    } else {        fmt.Printf("error %s\n", err.Error())    }}type Point1 struct {    X int    Y int}func (pt Point1) MarshalText() ([]byte, error) {    return []byte(fmt.Sprintf(`{"px" : %d, "py" : %d}`, pt.X, pt.Y)), nil}func encode_from_object_with_text_marshaler_interface() {    fmt.Printf("encode_from_object_with_text_marshaler_interface\n")    if data, err := json.Marshal(Point1{50, 50}); err == nil {        fmt.Printf("%s\n", data)    } else {        fmt.Printf("error %s\n", err.Error())    }}// decode testfunc decode_to_map_test() {    fmt.Printf("decode_to_map_test\n")    data := `[{"Level":"debug","Msg":"File: \"test.txt\" Not Found"},` +        `{"Level":"","Msg":"Logic error"}]`    var debug_infos []map[string]string    json.Unmarshal([]byte(data), &debug_infos)    fmt.Println(debug_infos)}type DebugInfo struct {    Level  string    Msg    string    author string // 未匯出欄位不會被json解析}func (dbgInfo DebugInfo) String() string {    return fmt.Sprintf("{Level: %s, Msg: %s}", dbgInfo.Level, dbgInfo.Msg)}func decode_to_object_test() {    fmt.Printf("decode_to_object_test\n")    data := `[{"level":"debug","msg":"File Not Found","author":"Cynhard"},` +        `{"level":"","msg":"Logic error","author":"Gopher"}]`    var dbgInfos []DebugInfo    json.Unmarshal([]byte(data), &dbgInfos)    fmt.Println(dbgInfos)}type DebugInfoTag struct {    Level  string `json:"level"`   // level 解碼為 Level    Msg    string `json:"message"` // message 解碼為 Msg    Author string `json:"-"`       // 忽略Author}func (dbgInfo DebugInfoTag) String() string {    return fmt.Sprintf("{Level: %s, Msg: %s}", dbgInfo.Level, dbgInfo.Msg)}func decode_to_object_tag_test() {    fmt.Printf("decode_to_object_tag_test\n")    data := `[{"level":"debug","message":"File Not Found","author":"Cynhard"},` +        `{"level":"","message":"Logic error","author":"Gopher"}]`    var dbgInfos []DebugInfoTag    json.Unmarshal([]byte(data), &dbgInfos)    fmt.Println(dbgInfos)}type Pointx struct{ X, Y int }type Circle struct {    Pointx    Radius int}func (c Circle) String() string {    return fmt.Sprintf("{Point{X: %d, Y :%d}, Radius: %d}",        c.Pointx.X, c.Pointx.Y, c.Radius)}func decode_to_object_with_anonymous_field() {    fmt.Printf("decode_to_object_with_anonymous_field\n")    data := `{"X":80,"Y":80,"Radius":40}`    var c Circle    json.Unmarshal([]byte(data), &c)    fmt.Println(c)}// decode convert interface// 解碼時根據參數是否滿足json.Unmarshaler和encoding.TextUnmarshaler來調用相應函數（若兩個函數都存在，則優先調用UnmarshalJSON）/*// json.Unmarshalertype Unmarshaler interface {    UnmarshalJSON([]byte) error}// encoding.TextUnmarshalertype TextUnmarshaler interface {    UnmarshalText(text []byte) error}*/type Pointy struct{ X, Y int }func (pt Pointy) MarshalJSON() ([]byte, error) {    // no decode, just print    return []byte(fmt.Sprintf(`{"X":%d,"Y":%d}`, pt.X, pt.Y)), nil}func decode_to_object_with_marshaler_interface() {    fmt.Printf("decode_to_object_with_marshaler_interface\n")    if data, err := json.Marshal(Pointy{50, 50}); err == nil {        fmt.Printf("%s\n", data)    }}func main() {    fmt.Println("json test!")    fmt.Printf("ecode test\n")    encode_from_map_test()    encode_from_object_test()    encode_from_object_tag_test()    encode_from_object_with_anonymous_field()    encode_from_object_with_marshaler_interface()    encode_from_object_with_text_marshaler_interface()    fmt.Printf("decode test\n")    decode_to_map_test()    decode_to_object_test()    decode_to_object_tag_test()    decode_to_object_with_anonymous_field()    decode_to_object_with_marshaler_interface()}

運行結果:

json test!ecode testencode_from_map_test{"level":["debug"],"message":["File not found","Stack overflow"]}encode_from_object_test[{"Game_id":1,"Game_map":"map1","Game_time":20},{"Game_id":2,"Game_map":"map2","Game_time":60}]encode_from_object_tag_test[{"game_id":1,"game_map":"map1","Game_time":20},{"game_id":2,"game_map":"map2","Game_time":60},{"game_id":3,"Game_time":120}]encode_from_object_with_anonymous_field{"Field_a":"a","Field_b":"b","Field_c":"c"}encode_from_object_with_marshaler_interface{"px":50,"py":50}encode_from_object_with_text_marshaler_interface"{\"px\" : 50, \"py\" : 50}"decode testdecode_to_map_test[map[Level:debug Msg:File: "test.txt" Not Found] map[Level: Msg:Logic error]]decode_to_object_test[{Level: debug, Msg: File Not Found} {Level: , Msg: Logic error}]decode_to_object_tag_test[{Level: debug, Msg: File Not Found} {Level: , Msg: Logic error}]decode_to_object_with_anonymous_field{Point{X: 80, Y :80}, Radius: 40}decode_to_object_with_marshaler_interface{"X":50,"Y":50}