FastJson源码解析：序列化（1.1.45.android）

本解析主要以JSON.toJSONString(Object)这个方法作为入口。以HashSet《POJO》作为例子。
#1

String s = JSON.toJSONString(beanSet);

以这个方法为入口，上面的beanSet为一个以POJO类为泛型的hashSet。
#2

public static final String toJSONString(Object object) {    return toJSONString(object, new SerializerFeature[0]);}public static final String toJSONString(Object object, SerializerFeature... features) {    //这里构建的过程中会将默认的SerializerFeature 加入的writer中    //详见下一个代码块#3    SerializeWriter out = new SerializeWriter();    try {        JSONSerializer serializer = new JSONSerializer(out);        for (SerializerFeature feature : features) {            serializer.config(feature, true);        }        //序列化的核心方法在此        //详见后面的代码块#5        serializer.write(object);        return out.toString();    } finally {        out.close();    }}

下面是SerializeWriter（继承自writer） 构造器代码
#3

public SerializeWriter(Writer writer){    this.writer = writer;    //这里会有一些默认的feature 后面会用到    this.features = JSON.DEFAULT_GENERATE_FEATURE;    SoftReference<char[]> ref = bufLocal.get();    if (ref != null) {        //buf是这个writer的缓存 char数组        buf = ref.get();        //bufLocal是一个threadLocal类型        bufLocal.set(null);    }    if (buf == null) {        buf = new char[1024];    }}

关于默认的features，在JSON中，静态初始化了这个成员变量，如下:
#4

public static int    DEFAULT_GENERATE_FEATURE;static {    int features = 0;    features |= SerializerFeature.QuoteFieldNames.getMask();    features |= SerializerFeature.SkipTransientField.getMask();    features |= SerializerFeature.WriteEnumUsingToString.getMask();    features |= SerializerFeature.SortField.getMask();    // features |=    // SerializerFeature.WriteSlashAsSpecial.getMask();    DEFAULT_GENERATE_FEATURE = features;}

由此可知，默认已经加入了QuoteFieldNames, SkipTransientField, WriteEnumUsingToString, SortField四个feature。
#5

public final void write(Object object) {    if (object == null) {        out.writeNull();        return;    }    Class<?> clazz = object.getClass();    //第一处核心代码在此    ObjectSerializer writer = getObjectWriter(clazz);    try {        //第二处核心逻辑在这里，这个代码被包住了        writer.write(this, object, null, null);    } catch (IOException e) {        //此处抛出异常        throw new JSONException(e.getMessage(), e);    }}

#6

public ObjectSerializer getObjectWriter(Class<?> clazz) {    ObjectSerializer writer = config.get(clazz);    if (writer == null) {        if (Map.class.isAssignableFrom(clazz)) {            config.put(clazz, MapSerializer.instance);        } else if (List.class.isAssignableFrom(clazz)) {            config.put(clazz, ListSerializer.instance);        } else if (Collection.class.isAssignableFrom(clazz)) {            //我们的逻辑（hashSet），应该进入了这里            config.put(clazz, CollectionSerializer.instance);        } else if (Date.class.isAssignableFrom(clazz)) {            config.put(clazz, DateSerializer.instance);        } else if (JSONAware.class.isAssignableFrom(clazz)) {            config.put(clazz, JSONAwareSerializer.instance);        } else if (JSONSerializable.class.isAssignableFrom(clazz)) {            config.put(clazz, JSONSerializableSerializer.instance);        } else if (JSONStreamAware.class.isAssignableFrom(clazz)) {            config.put(clazz, JSONStreamAwareSerializer.instance);        } else if (clazz.isEnum() || (clazz.getSuperclass() != null && clazz.getSuperclass().isEnum())) {            config.put(clazz, EnumSerializer.instance);        } else if (clazz.isArray()) {            Class<?> componentType = clazz.getComponentType();            ObjectSerializer compObjectSerializer = getObjectWriter(componentType);            config.put(clazz, new ArraySerializer(componentType, compObjectSerializer));        } else if (Throwable.class.isAssignableFrom(clazz)) {            config.put(clazz, new ExceptionSerializer(clazz));        } else if (TimeZone.class.isAssignableFrom(clazz)) {            config.put(clazz, TimeZoneCodec.instance);        } else if (Charset.class.isAssignableFrom(clazz)) {            config.put(clazz, CharsetCodec.instance);        } else if (Enumeration.class.isAssignableFrom(clazz)) {            config.put(clazz, EnumerationSeriliazer.instance);        } else if (Calendar.class.isAssignableFrom(clazz)) {            config.put(clazz, CalendarCodec.instance);        } else {            boolean isCglibProxy = false;            boolean isJavassistProxy = false;            for (Class<?> item : clazz.getInterfaces()) {                if (item.getName().equals("net.sf.cglib.proxy.Factory")                    || item.getName().equals("org.springframework.cglib.proxy.Factory")) {                    isCglibProxy = true;                    break;                } else if (item.getName().equals("javassist.util.proxy.ProxyObject")) {                    isJavassistProxy = true;                    break;                }            }            if (isCglibProxy || isJavassistProxy) {                Class<?> superClazz = clazz.getSuperclass();                ObjectSerializer superWriter = getObjectWriter(superClazz);                config.put(clazz, superWriter);                return superWriter;            }            if (Proxy.isProxyClass(clazz)) {                config.put(clazz, config.createJavaBeanSerializer(clazz));            } else {                //对于一般的POJO，应该进入了这里，见#8                config.put(clazz, config.createJavaBeanSerializer(clazz));            }        }        writer = config.get(clazz);    }    return writer;}

#7：CollectionSerializer序列化器的writer方法

public void write(JSONSerializer serializer, Object object, Object fieldName, Type fieldType) throws IOException {    SerializeWriter out = serializer.getWriter();    if (object == null) {        if (out.isEnabled(SerializerFeature.WriteNullListAsEmpty)) {            out.write("[]");        } else {            out.writeNull();        }        return;    }    Type elementType = null;    if (serializer.isEnabled(SerializerFeature.WriteClassName)) {        if (fieldType instanceof ParameterizedType) {            ParameterizedType param = (ParameterizedType) fieldType;            elementType = param.getActualTypeArguments()[0];        }    }    Collection<?> collection = (Collection<?>) object;    SerialContext context = serializer.getContext();    serializer.setContext(context, object, fieldName, 0);    if (serializer.isEnabled(SerializerFeature.WriteClassName)) {        if (HashSet.class == collection.getClass()) {            out.append("Set");        } else if (TreeSet.class == collection.getClass()) {            out.append("TreeSet");        }    }    try {        int i = 0;        out.append('[');        for (Object item : collection) {            if (i++ != 0) {                out.append(',');            }            if (item == null) {                out.writeNull();                continue;            }            Class<?> clazz = item.getClass();            if (clazz == Integer.class) {                out.writeInt(((Integer) item).intValue());                continue;            }            if (clazz == Long.class) {                out.writeLong(((Long) item).longValue());                if (out.isEnabled(SerializerFeature.WriteClassName)) {                    out.write('L');                }                continue;            }            //最终如果是集合内部一个Object,会调用对应的ObjectSerializer,这就回到了#6中的getObjectWriter代码，实际上会得到一个JavaBeanSerializer实例            ObjectSerializer itemSerializer = serializer.getObjectWriter(clazz);            itemSerializer.write(serializer, item, i - 1, elementType);        }        out.append(']');    } finally {        serializer.setContext(context);    }}

#8 SerializeConfig对于一般JavaBean的Serializer

public ObjectSerializer createJavaBeanSerializer(Class<?> clazz) {    return new JavaBeanSerializer(clazz);}

#9 JavaBeanSerializer最终的构造器

public JavaBeanSerializer(Class<?> clazz, Map<String, String> aliasMap){    this.features = TypeUtils.getSerializeFeatures(clazz);    //下面是两个代码块    {        List<FieldSerializer> getterList = new ArrayList<FieldSerializer>();        //核心逻辑在computeGetters这个方法中，获取了所有的getter,因为Android没有内省框架，所以这里是fastJson自行实现的        List<FieldInfo> fieldInfoList = TypeUtils.computeGetters(clazz, aliasMap, false);        for (FieldInfo fieldInfo : fieldInfoList) {            //这里将fieldInfo通过createFieldSerializer转换为FieldSerializer             getterList.add(createFieldSerializer(fieldInfo));        }        //最终放在getter这个FieldSerializer数组里        getters = getterList.toArray(new FieldSerializer[getterList.size()]);    }    {        List<FieldSerializer> getterList = new ArrayList<FieldSerializer>();        List<FieldInfo> fieldInfoList = TypeUtils.computeGetters(clazz, aliasMap, true);        for (FieldInfo fieldInfo : fieldInfoList) {            getterList.add(createFieldSerializer(fieldInfo));        }        sortedGetters = getterList.toArray(new FieldSerializer[getterList.size()]);    }}

#10 实际上返回的是ObjectFieldSerializer

public FieldSerializer createFieldSerializer(FieldInfo fieldInfo) {    Class<?> clazz = fieldInfo.getFieldClass();    //感觉这里写的有问题，是否应该是clazz.isAssignedFrom(Number.class)??,不然这个NumberFieldSerializer没可能用的上的吧？    if (clazz == Number.class) {        return new NumberFieldSerializer(fieldInfo);    }    return new ObjectFieldSerializer(fieldInfo);}

#11 ObjectFieldSerializer的构造器：

public ObjectFieldSerializer(FieldInfo fieldInfo){    super(fieldInfo);    JSONField annotation = fieldInfo.getAnnotation(JSONField.class);    if (annotation != null) {        format = annotation.format();        if (format.trim().length() == 0) {            format = null;        }        //这里会将JSONField annotation中feature的内容初始化为bool        for (SerializerFeature feature : annotation.serialzeFeatures()) {            if (feature == SerializerFeature.WriteNullNumberAsZero) {                writeNumberAsZero = true;            } else if (feature == SerializerFeature.WriteNullStringAsEmpty) {                writeNullStringAsEmpty = true;            } else if (feature == SerializerFeature.WriteNullBooleanAsFalse) {                writeNullBooleanAsFalse = true;            } else if (feature == SerializerFeature.WriteNullListAsEmpty) {                writeNullListAsEmpty = true;            } else if (feature == SerializerFeature.WriteEnumUsingToString) {                writeEnumUsingToString = true;            }        }    }}

#12 run too far 回到JavaBeanSerializer的write方法

public void write(JSONSerializer serializer, Object object, Object fieldName, Type fieldType) throws IOException {    SerializeWriter out = serializer.getWriter();    //见下#13，如果为空，直接过进入这里，写入字符串：null    if (object == null) {        out.writeNull();        return;    }    if (writeReference(serializer, object)) {        return;    }    final FieldSerializer[] getters;    if (out.isEnabled(SerializerFeature.SortField)) {        getters = this.sortedGetters;    } else {        getters = this.getters;    }    SerialContext parent = serializer.getContext();    serializer.setContext(parent, object, fieldName, features);    final boolean writeAsArray = isWriteAsArray(serializer);    try {        final char startSeperator = writeAsArray ? '[' : '{';        final char endSeperator = writeAsArray ? ']' : '}';        out.append(startSeperator);        if (getters.length > 0 && out.isEnabled(SerializerFeature.PrettyFormat)) {            serializer.incrementIndent();            serializer.println();        }        boolean commaFlag = false;        if (isWriteClassName(serializer, object, fieldType, fieldName)) {            Class<?> objClass = object.getClass();            if (objClass != fieldType) {                out.writeFieldName(JSON.DEFAULT_TYPE_KEY);                serializer.write(object.getClass());                commaFlag = true;            }        }        char seperator = commaFlag ? ',' : '\0';        char newSeperator = FilterUtils.writeBefore(serializer, object, seperator);        commaFlag = newSeperator == ',';        for (int i = 0; i < getters.length; ++i) {            FieldSerializer fieldSerializer = getters[i];            //这里会跳过Transient字段            if (serializer.isEnabled(SerializerFeature.SkipTransientField)) {                Field field = fieldSerializer.getField();                if (field != null) {                    if (Modifier.isTransient(field.getModifiers())) {                        continue;                    }                }            }            if (!FilterUtils.applyName(serializer, object, fieldSerializer.getName())) {                continue;            }            //这里拿出propertyValue             Object propertyValue = fieldSerializer.getPropertyValue(object);            if (!FilterUtils.apply(serializer, object, fieldSerializer.getName(), propertyValue)) {                continue;            }            String key = FilterUtils.processKey(serializer, object, fieldSerializer.getName(), propertyValue);            Object originalValue = propertyValue;            propertyValue = FilterUtils.processValue(serializer, object, fieldSerializer.getName(), propertyValue);            if (propertyValue == null && !writeAsArray) {                if ((!fieldSerializer.isWriteNull())                    && (!serializer.isEnabled(SerializerFeature.WriteMapNullValue))) {                    continue;                }            }            //注意propertyValue 这个字段，这里如果配置了为默认值的时候不写入，会进入这个if            if (propertyValue != null && serializer.isEnabled(SerializerFeature.NotWriteDefaultValue)) {                Class<?> fieldCLass = fieldSerializer.fieldInfo.getFieldClass();                if (fieldCLass == byte.class && propertyValue instanceof Byte && ((Byte)propertyValue).byteValue() == 0) {                    continue;                } else if (fieldCLass == short.class && propertyValue instanceof Short && ((Short)propertyValue).shortValue() == 0) {                    continue;                } else if (fieldCLass == int.class && propertyValue instanceof Integer && ((Integer)propertyValue).intValue() == 0) {                    continue;                } else if (fieldCLass == long.class && propertyValue instanceof Long && ((Long)propertyValue).longValue() == 0L) {                    continue;                } else if (fieldCLass == float.class && propertyValue instanceof Float && ((Float)propertyValue).floatValue() == 0F) {                    continue;                } else if (fieldCLass == double.class && propertyValue instanceof Double && ((Double)propertyValue).doubleValue() == 0D) {                    continue;                } else if (fieldCLass == boolean.class && propertyValue instanceof Boolean && !((Boolean)propertyValue).booleanValue()) {                    continue;                }            }            if (commaFlag) {                out.append(',');                if (out.isEnabled(SerializerFeature.PrettyFormat)) {                    serializer.println();                }            }            if (key != fieldSerializer.getName()) {                if (!writeAsArray) {                    out.writeFieldName(key);                }                serializer.write(propertyValue);            } else if (originalValue != propertyValue) {                if (!writeAsArray) {                    fieldSerializer.writePrefix(serializer);                }                serializer.write(propertyValue);            } else {                if (!writeAsArray) {                    fieldSerializer.writeProperty(serializer, propertyValue);                } else {                    fieldSerializer.writeValue(serializer, propertyValue);                }            }            //这个表示逗号是否写入            commaFlag = true;        }        FilterUtils.writeAfter(serializer, object, commaFlag ? ',' : '\0');        if (getters.length > 0 && out.isEnabled(SerializerFeature.PrettyFormat)) {            serializer.decrementIdent();            serializer.println();        }        out.append(endSeperator);    } catch (Exception e) {        throw new JSONException("write javaBean error", e);    } finally {        serializer.setContext(parent);    }}

/#13 ObjectFieldSerializer.writeValue方法，最终对于Field会进入这里

@Overridepublic void writeValue(JSONSerializer serializer, Object propertyValue) throws Exception {    if (format != null) {        serializer.writeWithFormat(propertyValue, format);        return;    }    if (runtimeInfo == null) {        Class<?> runtimeFieldClass;        if (propertyValue == null) {            runtimeFieldClass = this.fieldInfo.getFieldClass();        } else {            runtimeFieldClass = propertyValue.getClass();        }        //这里对于Field字段如何写入分配了对应的ObjectSerializer，一般应该是JavaBeanSerializer        ObjectSerializer fieldSerializer = serializer.getObjectWriter(runtimeFieldClass);        runtimeInfo = new RuntimeSerializerInfo(fieldSerializer, runtimeFieldClass);    }    final RuntimeSerializerInfo runtimeInfo = this.runtimeInfo;    //字段值为空的时候的处理    if (propertyValue == null) {        if (writeNumberAsZero && Number.class.isAssignableFrom(runtimeInfo.runtimeFieldClass)) {            serializer.getWriter().write('0');            return;        } else if (writeNullStringAsEmpty && String.class == runtimeInfo.runtimeFieldClass) {            serializer.getWriter().write("\"\"");            return;        } else if (writeNullBooleanAsFalse && Boolean.class == runtimeInfo.runtimeFieldClass) {            serializer.getWriter().write("false");            return;        } else if (writeNullListAsEmpty && Collection.class.isAssignableFrom(runtimeInfo.runtimeFieldClass)) {            serializer.getWriter().write("[]");            return;        }        //如果没有任何配置 则应该为是JavaBeanSerializer来处理，见#12        runtimeInfo.fieldSerializer.write(serializer, null, fieldInfo.getName(), null);        return;    }    if (writeEnumUsingToString == true && runtimeInfo.runtimeFieldClass.isEnum()) {        serializer.getWriter().writeString(((Enum<?>) propertyValue).name());        return;    }    Class<?> valueClass = propertyValue.getClass();    if (valueClass == runtimeInfo.runtimeFieldClass) {        runtimeInfo.fieldSerializer.write(serializer, propertyValue, fieldInfo.getName(), fieldInfo.getFieldType());        return;    }    ObjectSerializer valueSerializer = serializer.getObjectWriter(valueClass);    valueSerializer.write(serializer, propertyValue, fieldInfo.getName(), fieldInfo.getFieldType());}