fastjson简单使⽤demo，@JSONField注解属性字段上与set、
get⽅法上。。。
⼀、demo代码
@JSONField注解属性字段上与set、get⽅法上。使⽤@Data注解（lombok插件安装最下⽅），对属性“笔名”【pseudonym】⼿动重写setter/getter⽅法
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.annotation.JSONField;
import lombok.Data;
@Data
public class Stu {
private String name;
//下划线⾃动转换
private String alias_name;
//下划线⾃动转换
//    @JSONField(name="pen_name")
private String penName;
//实体类转为json，使⽤注解name值
@JSONField(name="pen_name2")
private String penName2;
private String pseudonym;
//实体类转为json，使⽤注解name值
@JSONField(name="pseud")
/
/不使⽤注解为属性名{"penName":"333","name":"1111","alias_name":"222","pen_name2":"444","pseudonym":"555"}
public String getPseudonym() {
return pseudonym;
}
//json转为实体类，使⽤注解name值
fastjson怎么用@JSONField(name="pseudo")
public void setPseudonym(String pseudonym) {
this.pseudonym = pseudonym;
}
public static void main(String[] args) {
String json = "{'name':'1111','aliasName':'222','pen_name':'333','pen_name2':'444','pseudo':'555'}";
Stu stu = JSON.parseObject(json, Stu.class);
System.out.println(stu);
System.out.JSON(stu));
}
}
⼆、main⽅法运⾏结果（控制台）
Stu(name=1111, alias_name=222, penName=333, penName2=444, pseudonym=555)
{"pseud":"555","penName":"333","name":"1111","alias_name":"222","pen_name2":"444"}
Process finished with exit code 0
三、@Data备注
idea安装lombok插件。
四、源码
类：
JavaBeanDeserializer implements ObjectDeserializer
public FieldDeserializer smartMatch(String key, int[] setFlags) {
if (key == null) {
return null;
} else {
FieldDeserializer fieldDeserializer = FieldDeserializer(key, setFlags);
if (fieldDeserializer == null) {
long smartKeyHash = TypeUtils.fnv1a_64_lower(key);
if (this.smartMatchHashArray == null) {
long[] hashArray = new long[this.sortedFieldDeserializers.length];
for(int i = 0; i < this.sortedFieldDeserializers.length; ++i) {
hashArray[i] = TypeUtils.fnv1a_64_lower(this.sortedFieldDeserializers[i].fieldInfo.name);
}
Arrays.sort(hashArray);
this.smartMatchHashArray = hashArray;
}
int pos = Arrays.binarySearch(this.smartMatchHashArray, smartKeyHash);
boolean is = false;
if (pos < 0 && (is = key.startsWith("is"))) {
smartKeyHash = TypeUtils.fnv1a_64_lower(key.substring(2));
pos = Arrays.binarySearch(this.smartMatchHashArray, smartKeyHash);
}
if (pos >= 0) {
if (this.smartMatchHashArrayMapping == null) {
short[] mapping = new short[this.smartMatchHashArray.length];
Arrays.fill(mapping, (short)-1);
for(int i = 0; i < this.sortedFieldDeserializers.length; ++i) {
int p = Arrays.binarySearch(this.smartMatchHashArray, TypeUtils.fnv1a_64_lower(this.sortedFieldDeserializers[i].fieldInfo.name));                            if (p >= 0) {
mapping[p] = (short)i;
}
}
this.smartMatchHashArrayMapping = mapping;
}
int deserIndex = this.smartMatchHashArrayMapping[pos];
if (deserIndex != -1 && !isSetFlag(deserIndex, setFlags)) {
fieldDeserializer = this.sortedFieldDeserializers[deserIndex];
}
}
if (fieldDeserializer != null) {
FieldInfo fieldInfo = fieldDeserializer.fieldInfo;
if ((fieldInfo.parserFeatures & Feature.DisableFieldSmartMatch.mask) != 0) {
return null;
}
Class fieldClass = fieldInfo.fieldClass;
if (is && fieldClass != Boolean.TYPE && fieldClass != Boolean.class) {
fieldDeserializer = null;
}
}
}
return fieldDeserializer;
}
}
“_”下划线及“-”短横线（减号），⼤⼩写都可以智能匹配。
类：
TypeUtils
public static long fnv1a_64_lower(String key) {
long hashCode = -3750763034362895579L;
for(int i = 0; i < key.length(); ++i) {
char ch = key.charAt(i);
if (ch != '_' && ch != '-') {
if (ch >= 'A' && ch <= 'Z') {
ch = (char)(ch + 32);
}
hashCode ^= (long)ch;
hashCode *= 1099511628211L;
}
}
return hashCode;
}
五、JackSon
@JsonProperty
这个注解提供了序列化和反序列化过程中该java属性所对应的名称。
Access.WRITE_ONLY：只在序列化时使⽤修改后的字段
Access.READ_ONLY：只在反序列化时使⽤，类似于@JsonAlias注解
Access.READ_WRITE：在序列化和反序列化都使⽤修改后字段
Access.AUTO：⾃动确定
@JsonAlias
这个注解是在JackSon 2.9版本中才有的。
作⽤是在反序列化的时候可以让Bean的属性接收多个json字段的名称。可以加在字段上或者getter和setter⽅法上

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