本文主要是介绍FastJson对复杂的泛型对象的解析问题，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
首先要说的是FastJson提供了一个用于处理泛型反序列化的类TypeReference,在知道具体泛型类型的情况下可以实现反序列化，这里由于应用场景不适用不对其进行讨论。
如下场景：
public class PieChartVO<T extends BaseDebtVO> implements Serializable {private static final long serialVersionUID = -6422895776727574355L;private BigDecimal avgYearRate;private ArrayList<T> transVOs;public BigDecimal getAvgYearRate() {return avgYearRate;}public void setAvgYearRate(BigDecimal avgYearRate) {this.avgYearRate = avgYearRate;}public ArrayList<T> getTransVOs() {return transVOs;}public void setTransVOs(ArrayList<T> transVOs) {this.transVOs = transVOs;} }
public class CreditorDebtVO extends BaseDebtVO {private static final long serialVersionUID = -254172337494852158L;private BigDecimal totalEarning;public BigDecimal getTotalEarning() {return totalEarning;}public void setTotalEarning(BigDecimal totalEarning) {this.totalEarning = totalEarning;}}
public class ObligorDebtVO extends BaseDebtVO {private static final long serialVersionUID = 3314361571700869005L;private Integer overdueCount;private BigDecimal overdueOtherFee;public Integer getOverdueCount() {return overdueCount;}public void setOverdueCount(Integer overdueCount) {this.overdueCount = overdueCount;}public BigDecimal getOverdueOtherFee() {return overdueOtherFee;}public void setOverdueOtherFee(BigDecimal overdueOtherFee) {this.overdueOtherFee = overdueOtherFee;} }
{"body": {"avgYearRate": 14.8, "transVOs": [{"avgRate": 19.2, "cleanCount": 8, "id": 15, "subTitle": "aaa", "title": "bbb", "totalEarning": 20.75, "totalPrincipal": 17000, "transCount": 3, "transMoney": 4698.93, "transOverdueMoney": 0}]}, "result": 1 }
对于获取到的json数据并不知道具体的泛型类型，也就没法指定的情况下，解决方案是对反序列化进行自定义定制，fastJson自身对基础的field内置了许多反序列化器，当对json反序列化时，会根据filed的class找到相应的反序列化器来执行反序列化。
public class ParserConfig {private final IdentityHashMap<Type, ObjectDeserializer> deserializers = new IdentityHashMap<Type, ObjectDeserializer>();/**省略了其他代码*/private void initDeserializers() {deserializers.put(SimpleDateFormat.class, MiscCodec.instance);deserializers.put(java.sql.Timestamp.class, SqlDateDeserializer.instance_timestamp);deserializers.put(java.sql.Date.class, SqlDateDeserializer.instance);deserializers.put(java.sql.Time.class, TimeDeserializer.instance);deserializers.put(java.util.Date.class, DateCodec.instance);deserializers.put(Calendar.class, CalendarCodec.instance);deserializers.put(XMLGregorianCalendar.class, CalendarCodec.instance);deserializers.put(JSONObject.class, MapDeserializer.instance);deserializers.put(JSONArray.class, CollectionCodec.instance);deserializers.put(Map.class, MapDeserializer.instance);deserializers.put(HashMap.class, MapDeserializer.instance);deserializers.put(LinkedHashMap.class, MapDeserializer.instance);deserializers.put(TreeMap.class, MapDeserializer.instance);deserializers.put(ConcurrentMap.class, MapDeserializer.instance);deserializers.put(ConcurrentHashMap.class, MapDeserializer.instance);deserializers.put(Collection.class, CollectionCodec.instance);deserializers.put(List.class, CollectionCodec.instance);deserializers.put(ArrayList.class, CollectionCodec.instance);deserializers.put(Object.class, JavaObjectDeserializer.instance);deserializers.put(String.class, StringCodec.instance);deserializers.put(StringBuffer.class, StringCodec.instance);deserializers.put(StringBuilder.class, StringCodec.instance);deserializers.put(char.class, CharacterCodec.instance);deserializers.put(Character.class, CharacterCodec.instance);deserializers.put(byte.class, NumberDeserializer.instance);deserializers.put(Byte.class, NumberDeserializer.instance);deserializers.put(short.class, NumberDeserializer.instance);deserializers.put(Short.class, NumberDeserializer.instance);deserializers.put(int.class, IntegerCodec.instance);deserializers.put(Integer.class, IntegerCodec.instance);deserializers.put(long.class, LongCodec.instance);deserializers.put(Long.class, LongCodec.instance);deserializers.put(BigInteger.class, BigIntegerCodec.instance);deserializers.put(BigDecimal.class, BigDecimalCodec.instance);deserializers.put(float.class, FloatCodec.instance);deserializers.put(Float.class, FloatCodec.instance);deserializers.put(double.class, NumberDeserializer.instance);deserializers.put(Double.class, NumberDeserializer.instance);deserializers.put(boolean.class, BooleanCodec.instance);deserializers.put(Boolean.class, BooleanCodec.instance);deserializers.put(Class.class, MiscCodec.instance);deserializers.put(char[].class, new CharArrayCodec());deserializers.put(AtomicBoolean.class, BooleanCodec.instance);deserializers.put(AtomicInteger.class, IntegerCodec.instance);deserializers.put(AtomicLong.class, LongCodec.instance);deserializers.put(AtomicReference.class, ReferenceCodec.instance);deserializers.put(WeakReference.class, ReferenceCodec.instance);deserializers.put(SoftReference.class, ReferenceCodec.instance);deserializers.put(UUID.class, MiscCodec.instance);deserializers.put(TimeZone.class, MiscCodec.instance);deserializers.put(Locale.class, MiscCodec.instance);deserializers.put(Currency.class, MiscCodec.instance);deserializers.put(InetAddress.class, MiscCodec.instance);deserializers.put(Inet4Address.class, MiscCodec.instance);deserializers.put(Inet6Address.class, MiscCodec.instance);deserializers.put(InetSocketAddress.class, MiscCodec.instance);deserializers.put(File.class, MiscCodec.instance);deserializers.put(URI.class, MiscCodec.instance);deserializers.put(URL.class, MiscCodec.instance);deserializers.put(Pattern.class, MiscCodec.instance);deserializers.put(Charset.class, MiscCodec.instance);deserializers.put(JSONPath.class, MiscCodec.instance);deserializers.put(Number.class, NumberDeserializer.instance);deserializers.put(AtomicIntegerArray.class, AtomicCodec.instance);deserializers.put(AtomicLongArray.class, AtomicCodec.instance);deserializers.put(StackTraceElement.class, StackTraceElementDeserializer.instance);deserializers.put(Serializable.class, JavaObjectDeserializer.instance);deserializers.put(Cloneable.class, JavaObjectDeserializer.instance);deserializers.put(Comparable.class, JavaObjectDeserializer.instance);deserializers.put(Closeable.class, JavaObjectDeserializer.instance);deserializers.put(JSONPObject.class, new JSONPDeserializer());}public ObjectDeserializer getDeserializer(Class<?> clazz, Type type) {/** 首先从内部已经注册查找特定type的反序列化实例 */ObjectDeserializer derializer = deserializers.get(type);if (derializer != null) {return derializer;}.......}}
可以看到对于ArrayList的默认的反序列化器是CollectionCodec，另外fastjson还提供了@JSONField注解对field可以有一些自定义的处理，其deserializeUsing属性可以指定具体的反序列化器。我们要做的就很简单了。
自定义反序列化器实现CollectionCodec，具体的反序列化工作仍然交由CollectionCodec处理，只不过须要对得到的对象进行自定义的加工。这里通过判断某个field是否存在来决定以哪个类来反序列化。
public class DebtVODeserializer extends CollectionCodec {@Overridepublic <T> T deserialze(DefaultJSONParser parser, Type type, Object fieldName) {T list = super.deserialze(parser, type, fieldName);JSONArray jsonArray = JSON.parseArray(JSON.toJSONString(list));ArrayList<CreditorDebtVO> debtVOs = new ArrayList<>();if (jsonArray != null && jsonArray.size()>0){if (jsonArray.getJSONObject(0).get("totalEarning")!=null){ArrayList<CreditorDebtVO> creditorDebtVOList = (ArrayList<CreditorDebtVO>)JSON.parseArray(JSON.toJSONString(list),CreditorDebtVO.class);return (T)creditorDebtVOList;} else if (jsonArray.getJSONObject(0).get("overdueOtherFee")!=null){ArrayList<ObligorDebtVO> obligorDebtVOList = (ArrayList<ObligorDebtVO>)JSON.parseArray(JSON.toJSONString(list),ObligorDebtVO.class);return (T)obligorDebtVOList;}} else {return list;}return (T)debtVOs;} }
修改PieChartVO，指定自定义的反序列化器
@JSONField(deserializeUsing = DebtVODeserializer.class)public void setTransVOs(ArrayList<T> transVOs) {this.transVOs = transVOs;}
PieChartVO vo = JSON.parseObject(json,PieChartVO.class);
如上，直接反序列化即可，对于使用方而言，不需要判断用哪个类来反序列化，代码上看简洁了许多...
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