golang中使用json

golang中使用json的一些例子

// go_json_test project main.go
package main
import (
 "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解析为game_id
 Game_map string `json:"game_map,omitempty"` // GameMap解析为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
// 在调用Marshal(v interface{})时,该函数会判断v是否满足json.Marshaler或者 encoding.Marshaler 接口,
// 如果满足,则会调用这两个接口来进行转换(如果两个都满足,优先调用json.Marshaler)
/*
// json.Marshaler
type Marshaler interface {
 MarshalJSON() ([]byte, error)
}
// encoding.TextMarshaler
type 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 test
func 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 // 未导出字段不会被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 解码为 Level
 Msg string `json:"message"` // message 解码为 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
// 解码时根据参数是否满足json.Unmarshaler和encoding.TextUnmarshaler来调用相应函数(若两个函数都存在,则优先调用UnmarshalJSON)
/*
// json.Unmarshaler
type Unmarshaler interface {
 UnmarshalJSON([]byte) error
}
// encoding.TextUnmarshaler
type 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()
}

运行结果:

json test!
ecode test
encode_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 test
decode_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}

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