【daily】Java枚举-fastjson对enum的处理⽬的
1、枚举值转换成完全的json；
2、对象中的枚举成员完全转换成json；
3、枚举类的全部值转换成json；
枚举定义
public enum SongsEnum {
SAFE_AND_SOUND(1,"Taylor Swift","Safe&Sound","2011-12-26")
,SHAKE_IT_OFF(2,"Taylor Swift","Shake It Off","2014-08-19")
,STYLE(3,"Taylor Swift","Style","2015-02-09")
,SOUND_OF_SILENCE(4,"Simon & Garfunkel","The Sound Of Silence","1966-01-17")
,BETTER_MAN(5,"Little Big Town","Better Man","2016-10-20")
,
YESTERDAY_ONCE_MORE(6,"Carpenters","Yesterday Once More","1973-05-16")
;
public final int index;
public final String singer;
public final String name;
public final String date;
private SongsEnum(int seq, String singer, String name, String date) {
this.index = seq;
this.singer = singer;
this.name = name;
this.date = date;
}
public int getIndex() { return index; }
public String getSinger() { return singer; }
public String getName() { return name; }
public String getDate() { return date; }
}
⼀、枚举值转换json
期望结果：SongsEnum.SAFE_AND_SOUND -> {"date":"2011-12-26","index":1,"name":"Safe&Sound","singer":"Taylor Swift"}
## 默认调⽤结果
默认的使⽤fastjson转换enum，那么得到的enum json可能不是想要的.
(1) 重写enum的toString()
@Override
public String toString() {
return "{'name':"+this.name+",'singer':"+this.singer+"}";
}
虽然可以这样得到想要的结果，但相对来说太⿇烦，每个enum类都要从写toString().
(此种⽅式并没有研究，所以以上重写toString()的代码可能存在问题)
(2) fastjson的config设置
fastjson提供的JSONString(...)有很多重载的⽅法，例如：
public static String toJSONString(Object object, SerializeConfig config, features)
所以，fastjson可以通过设置SerializeConfig来配置enum的序列化。
public static void main(String[] args) {
SerializeConfig config = new SerializeConfig();
String s = JSONString(SongsEnum.SOUND_OF_SILENCE, config);
System.out.println(s);
// {"date":"1966-01-17","index":4,"name":"The Sound Of Silence","singer":"Simon & Garfunkel"}
}
⼆、对象中的枚举成员完全转换成json
public enum StatusEnum {
STATUS_A(0,"状态A"),
STATUS_B(1,"状态B"),
STATUS_C(2,"状态C");
public final int index;
public final String status;
StatusEnum(int i, String status) {
this.index = i;
this.status = status;
}
public int getIndex() { return index; }
public String getStatus() { return status; }
}
class JavaBean{
private String name;
private SongsEnum song;
private StatusEnum status;
public JavaBean(String name,SongsEnum song,StatusEnum status){
this.name = name;
this.song = song;
this.status = status;
}
//省略setter/getter
}
期望: {"name":"vegilyn","song":{"date":"2014-08-19","index":2,"name":"Shake It Off","singer":"Taylor Swift"},"status":{"index":1,"status":"状态B"}}
默认结果:
SerializeConfig config = new SerializeConfig();
String s = JSONString(new JavaBean("vegilyn",SongsEnum.SHAKE_IT_OFF,StatusEnum.STATUS_B),config);
System.out.println(s);
// {"name":"vegilyn","song":{"date":"2014-08-19","index":2,"name":"Shake It Off","singer":"Taylor Swift"},"status":"STATUS_B"}
SerializeConfig config = new SerializeConfig();
String s = JSONString(new JavaBean("vegilyn",SongsEnum.SHAKE_IT_OFF,StatusEnum.STATUS_B),config);
System.out.println(s);
// {"name":"vegilyn","song":{"date":"2014-08-19","index":2,"name":"Shake It Off","singer":"Taylor Swift"},"status":{"index":1,"status":"状态B"}}
特别枚举数组转换的json：(注意重复值的json值)
public static void main(String[] args) {
SongsEnum[] songsEnums = {SongsEnum.BETTER_MAN, SongsEnum.SAFE_AND_SOUND, SongsEnum.BETTER_MAN};
SerializeConfig config = new SerializeConfig();
System.out.JSONString(songsEnums,config));
}
// [{"date":"2016-10-20","index":5,"name":"Better Man","singer":"Little Big Town"},{"date":"2011-12-26","index":1,"name":"Safe&Sound","singer":"Taylor Swift"},{"$ref":"$[0]"}]
三、枚举类的全部值转换成json
期望结果：
[
{"index": 1, "singer": "Taylor Swift", "name": "Safe&Sound", "date": "2011-12-26"},
{"index": 2, "singer": "Taylor Swift", "name": "Shake It Off", "date": "2014-08-19"},
{"index": 3, "singer": "Taylor Swift", "name": "Style", "date": "2015-02-09"},
{"index": 4, "singer": "Simon & Garfunkel", "name": "The Sound Of Silence", "date": "1966-01-17"},
{"index": 5, "singer": "Little Big Town", "name": "Better Man", "date": "2016-10-20"},
{"index": 6, "singer": "Carpenters", "name": "Yesterday Once More", "date": "1973-05-16"}
]
实现代码：
public static void main(String[] args) {
SongsEnum[] values = SongsEnum.values();
List<SongsEnum> songsEnums = new ArrayList<SongsEnum>();
for (SongsEnum value : values) {
songsEnums.add(value);
}
SerializeConfig config = new SerializeConfig();
System.out.JSONString(songsEnums, config));
}
以上能达到想要的效果，但是，每个enum类都要重复写以上代码。所以，利⽤反射来写⼀个公共的⽅法。
public static String toJson(Class<? extends Enum> enumClass) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {        Method methodValues = Method("values");
Object invoke = methodValues.invoke(null);
int length = Length(invoke);
List<Object> values = new ArrayList<Object>();
for (int i=0; i<length; i++) {
values.add((invoke, i));
}
SerializeConfig config = new SerializeConfig();
JSONString(values,config);
}
public static void main(String[] args) {
try {
System.out.Json(StatusEnum.class));
// [{"index":0,"status":"状态A"},{"index":1,"status":"状态B"},{"index":2,"status":"状态C"}]
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
四、扩展：fastjson如何得到enum的field定义。
通过jdk反射机制得到的field。
public static void main(String[] args) {
Field[] fields = Fields();
for (Field field : fields) {
System.out.Name());
}
}
SAFE_AND_SOUND
SHAKE_IT_OFF
STYLE
SOUND_OF_SILENCE
BETTER_MAN
YESTERDAY_ONCE_MORE
index
singer
name
date
如上，如果是通过jdk反射机制得到class的filed。会发现得到了不想要的结果，ex: SAFE_AND_SOUND 、SHAKE_IT_OFF 等。
想得到的field其实只想要: index、singer、name、date。
当然也可以⾃⼰分析，然后过滤出⾃⼰想要的class的field。
但下⾯看下fastjson中怎么得到enum中期望的field。(fastjson版本：1.2.31)
(1) 跟踪代码:  new SerializeConfig().configEnumAsJavaBean(enumClass)
public void configEnumAsJavaBean(Class<? extends Enum>... enumClasses) {
for (Class<? extends Enum> enumClass : enumClasses) {
put(enumClass, createJavaBeanSerializer(enumClass));
}
}
private final ObjectSerializer createJavaBeanSerializer(Class<?> clazz) {
SerializeBeanInfo beanInfo = TypeUtils.buildBeanInfo(clazz, null, propertyNamingStrategy, fieldBase);
if (beanInfo.fields.length == 0 && Iterable.class.isAssignableFrom(clazz)) {
return MiscCodec.instance;
}
return createJavaBeanSerializer(beanInfo);
}
public class SerializeBeanInfo {
protected final Class<?> beanType;
protected final String  typeName;
protected final JSONType jsonType;
protected final FieldInfo[] fields;
protected final FieldInfo[] sortedFields;
protected int              features;
public SerializeBeanInfo(Class<?> beanType, //
JSONType jsonType, //
String typeName, //
int features,
FieldInfo[] fields, //
FieldInfo[] sortedFields
){
this.beanType = beanType;
this.jsonType = jsonType;
this.features = features;
this.fields = fields;
this.sortedFields = sortedFields;
}
}
可以看到SerializeBeanInfo 中定义的有 fields 。
(很好奇为什么定义成protected , TyoeUtils.buildBeanInfo(...)是public的，返回的SerializeBeanInfo 也是public。但是，SerializeBeanInfo. fields却是protected的。
导致我知道fastjson中有这么⼀个util⽅法，可以得到我想要的enum信息（更确切的是可以得到class的信息）。但是，最后我并不能直接在我的代码中使⽤SerializeBeanInfo。)。
通过debug可以看到SerializeBeanInfo对象的属性，就是我想要的结果。
接着进去看TyoeUtils.buildBeanInfo(...)的实现：
public static SerializeBeanInfo buildBeanInfo(Class<?> beanType //
, Map<String, String> aliasMap //
, PropertyNamingStrategy propertyNamingStrategy //
, boolean fieldBased //
) {
JSONType jsonType = Annotation(JSONType.class);
// fieldName,field ，先⽣成fieldName的快照，减少之后的findField的轮询
Map<String, Field> fieldCacheMap = new HashMap<String, Field>();
ParserConfig.parserAllFieldToCache(beanType, fieldCacheMap);
List<FieldInfo> fieldInfoList = fieldBased
? computeGettersWithFieldBase(beanType, aliasMap, false, propertyNamingStrategy) //
: computeGetters(beanType, jsonType, aliasMap, fieldCacheMap, false, propertyNamingStrategy); // 省略...
}
执⾏computeGetters(...)的结果：
public static List<FieldInfo> computeGetters(Class<?> clazz, //
JSONType jsonType, //
Map<String, String> aliasMap, //
Map<String, Field> fieldCacheMap, //
boolean sorted, //
PropertyNamingStrategy propertyNamingStrategy //
) {
Map<String, FieldInfo> fieldInfoMap = new LinkedHashMap<String, FieldInfo>();
for (Method method : Methods()) {
String methodName = Name();
int ordinal = 0, serialzeFeatures = 0, parserFeatures = 0;
String label = null;
if (Modifier.Modifiers())) { continue; }  // 跳过static method
if (ReturnType().equals(Void.TYPE)) { continue; }
if (ParameterTypes().length != 0) { continue; }
if (ReturnType() == ClassLoader.class) { continue; }
if (Name().equals("getMetaClass")
&& ReturnType().getName().equals("groovy.lang.MetaClass")) {
continue;
}
JSONField annotation = Annotation(JSONField.class);
if (annotation == null) {
annotation = getSuperMethodAnnotation(clazz, method);
}
if (annotation != null) {
if (!annotation.serialize()) { continue; }
ordinal = dinal();
serialzeFeatures = SerializerFeature.of(annotation.serialzeFeatures());
parserFeatures = Feature.of(annotation.parseFeatures());
if (annotation.name().length() != 0) {
String propertyName = annotation.name();
if (aliasMap != null) {
propertyName = (propertyName);
if (propertyName == null) {
continue;
}
}
FieldInfo fieldInfo = new FieldInfo(propertyName, method, null, clazz, null, ordinal,
serialzeFeatures, parserFeatures, annotation, null, label);
fieldInfoMap.put(propertyName, fieldInfo);
continue;
}
if (annotation.label().length() != 0) {
label = annotation.label();
}
}
if (methodName.startsWith("get")) {
if (methodName.length() < 4) { continue; }
if (methodName.equals("getClass")) { continue;}
if (methodName.equals("getDeclaringClass") && clazz.isEnum()) { continue; }
char c3 = methodName.charAt(3);
fastjson忽略属性String propertyName;
if (Character.isUpperCase(c3) //
|| c3 > 512 // for unicode method name
) {
if (compatibleWithJavaBean) {
propertyName = decapitalize(methodName.substring(3));
} else {
propertyName = LowerCase(methodName.charAt(3)) + methodName.substring(4);
}
propertyName = getPropertyNameByCompatibleFieldName(fieldCacheMap, methodName,  propertyName,3);                } else if (c3 == '_') {
propertyName = methodName.substring(4);
} else if (c3 == 'f') {
propertyName = methodName.substring(3);
} else if (methodName.length() >= 5 && Character.isUpperCase(methodName.charAt(4))) {
propertyName = decapitalize(methodName.substring(3));
} else {
continue;
}
boolean ignore = isJSONTypeIgnore(clazz, propertyName);
if (ignore) {
continue;
}
//假如bean的field很多的情况⼀下，轮询时将⼤⼤降低效率
Field field = FieldFromCache(propertyName, fieldCacheMap);
if (field == null && propertyName.length() > 1) {
char ch = propertyName.charAt(1);

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