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详解golang的json解析方法Marshal跟 Unmarshal（复杂的对象直接用神器生成对象）
source link: https://blog.51cto.com/u_12040959/5147475
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详解golang的json解析方法Marshal跟 Unmarshal（复杂的对象直接用神器生成对象）
原创1.导入包
import (
"encoding/json"
"fmt"
)
"encoding/json"
"fmt"
)
2.对象结构
type Person struct {
Name string
Weight int
}
Name string
Weight int
}
要求：对象的字段名一定是大写字母开头，不然解析会报错，如果字段打上json标签就用标签的key,标签需要小写开头
如Name旁边的 json:"name"。
循环的对象（比如树，链表等等）不能用json，不然会使，marshal陷入循环
type Person struct {
Name string `json:"name"`
Weight int
}
Name string `json:"name"`
Weight int
}
func main() {
person := &Person{
Name: "hdf",
Weight: 145,
}
b,_ := json.Marshal(person)
var p Person
json.Unmarshal(b,&p)
fmt.Println(p)
os.Stdout.Write(b)
}
person := &Person{
Name: "hdf",
Weight: 145,
}
b,_ := json.Marshal(person)
var p Person
json.Unmarshal(b,&p)
fmt.Println(p)
os.Stdout.Write(b)
}
b是字节对象，p是person对象
4.源码解读
func Marshal(v interface{}) ([]byte, error) {
e := newEncodeState()
err := e.marshal(v, encOpts{escapeHTML: true})
if err != nil {
return nil, err
}
buf := append([]byte(nil), e.Bytes()...)
encodeStatePool.Put(e)
return buf, nil
}
e := newEncodeState()
err := e.marshal(v, encOpts{escapeHTML: true})
if err != nil {
return nil, err
}
buf := append([]byte(nil), e.Bytes()...)
encodeStatePool.Put(e)
return buf, nil
}
func (e *encodeState) marshal(v interface{}, opts encOpts) (err error) {
defer func() {
if r := recover(); r != nil {
if je, ok := r.(jsonError); ok {
err = je.error
} else {
panic(r)
}
}
}()
e.reflectValue(reflect.ValueOf(v), opts)
return nil
}
defer func() {
if r := recover(); r != nil {
if je, ok := r.(jsonError); ok {
err = je.error
} else {
panic(r)
}
}
}()
e.reflectValue(reflect.ValueOf(v), opts)
return nil
}
很明显用到了反射，
func Unmarshal(data []byte, v interface{}) error {
// Check for well-formedness.
// Avoids filling out half a data structure
// before discovering a JSON syntax error.
var d decodeState
err := checkValid(data, &d.scan)
if err != nil {
return err
}
d.init(data)
return d.unmarshal(v)
}
// Check for well-formedness.
// Avoids filling out half a data structure
// before discovering a JSON syntax error.
var d decodeState
err := checkValid(data, &d.scan)
if err != nil {
return err
}
d.init(data)
return d.unmarshal(v)
}
func (d *decodeState) unmarshal(v interface{}) error {
rv := reflect.ValueOf(v)
if rv.Kind() != reflect.Ptr || rv.IsNil() {
return &InvalidUnmarshalError{reflect.TypeOf(v)}
}
d.scan.reset()
d.scanWhile(scanSkipSpace)
// We decode rv not rv.Elem because the Unmarshaler interface
// test must be applied at the top level of the value.
err := d.value(rv)
if err != nil {
return d.addErrorContext(err)
}
return d.savedError
}
rv := reflect.ValueOf(v)
if rv.Kind() != reflect.Ptr || rv.IsNil() {
return &InvalidUnmarshalError{reflect.TypeOf(v)}
}
d.scan.reset()
d.scanWhile(scanSkipSpace)
// We decode rv not rv.Elem because the Unmarshaler interface
// test must be applied at the top level of the value.
err := d.value(rv)
if err != nil {
return d.addErrorContext(err)
}
return d.savedError
}
Unmarshal传递的是个指针。否则解析虽不报错，但数据无法赋值到接受体中。
5.复杂的结构体如何解析到对象
https://mholt.github.io/json-to-go/
推荐这个神器可以自动生成对象，非常的好用
如果这篇文章帮到了你，希望你可以帮小编投投票，47号峰啊疯了，投完可以抽奖哦
https://blog.51cto.com/blog-contest/index#part4
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