public <T> T readValue(String content, Class<T> valueType)
    throws IOException, JsonParseException, JsonMappingException
  {
    return (T) _readMapAndClose(_jsonFactory.createParser(content), _typeFactory.constructType(valueType));
  } 

  //获取json解析器，其中包含带解析的串
  public JsonParser createParser(String content) throws IOException, JsonParseException {
    final int strLen = content.length();
    // Actually, let's use this for medium-sized content, up to 64kB chunk (32kb char)
    if (_inputDecorator != null || strLen > 0x8000 || !canUseCharArrays()) {
      // easier to just wrap in a Reader than extend InputDecorator; or, if content
      // is too long for us to copy it over
      return createParser(new StringReader(content));
    }
    IOContext ctxt = _createContext(content, true);
    char[] buf = ctxt.allocTokenBuffer(strLen);
    content.getChars(0, strLen, buf, 0);
    return _createParser(buf, 0, strLen, ctxt, true);
  }

  //将待解析的类型转化为JavaType类型
  public JavaType constructType(Type type) {
    return _constructType(type, null);
  }
    protected JavaType _constructType(Type type, TypeBindings context)
  {
    JavaType resultType;
    // simple class?
    if (type instanceof Class<?>) {
      resultType = _fromClass((Class<?>) type, context);
    }
    // But if not, need to start resolving.
    else if (type instanceof ParameterizedType) {
      resultType = _fromParamType((ParameterizedType) type, context);
    }
    else if (type instanceof JavaType) { // [Issue#116]
      return (JavaType) type;
    }
    else if (type instanceof GenericArrayType) {
      resultType = _fromArrayType((GenericArrayType) type, context);
    }
    else if (type instanceof TypeVariable<?>) {
      resultType = _fromVariable((TypeVariable<?>) type, context);
    }
    else if (type instanceof WildcardType) {
      resultType = _fromWildcard((WildcardType) type, context);
    } else {
      // sanity check
      throw new IllegalArgumentException("Unrecognized Type: "+((type == null) ? "[null]" : type.toString()));
    }
    if (_modifiers != null && !resultType.isContainerType()) {
      for (TypeModifier mod : _modifiers) {
        resultType = mod.modifyType(resultType, type, context, this);
      }
    }
    return resultType;
  }

   protected Object _readMapAndClose(JsonParser jp, JavaType valueType)
    throws IOException, JsonParseException, JsonMappingException
  {
    try {
      Object result;
        DeserializationConfig cfg = getDeserializationConfig();
        DeserializationContext ctxt = createDeserializationContext(jp, cfg);
        //依据valueType得到反序列化的解析器
        // 对象对应的是beanDeserializer map对应的是MapDeserializer 。。。。
        JsonDeserializer<Object> deser = _findRootDeserializer(ctxt, valueType);
        if (cfg.useRootWrapping()) {
          result = _unwrapAndDeserialize(jp, ctxt, cfg, valueType, deser);
        } else {
         //如果是对象，则调到BeanDeserializer类中进行解析
          result = deser.deserialize(jp, ctxt);
        }
        ctxt.checkUnresolvedObjectId();
      }
      // Need to consume the token too
      jp.clearCurrentToken();
      return result;
    } finally {
      try {
        jp.close();
      } catch (IOException ioe) { }
    }
  }

  下面以BeanDeserializer为例进行讲解：
    @Override
  public Object deserialize(JsonParser p, DeserializationContext ctxt)
    throws IOException
  {
    JsonToken t = p.getCurrentToken();
    // common case first
    if (t == JsonToken.START_OBJECT) { // TODO: in 2.6, use 'p.hasTokenId()'
      if (_vanillaProcessing) {
        return vanillaDeserialize(p, ctxt, p.nextToken());
      }
      p.nextToken();
      if (_objectIdReader != null) {
        return deserializeWithObjectId(p, ctxt);
      }
      return deserializeFromObject(p, ctxt);
    }
    return _deserializeOther(p, ctxt, t);
  }

  /**
   * Streamlined version that is only used when no "special"
   * features are enabled.
   */
  private final Object vanillaDeserialize(JsonParser p,
    DeserializationContext ctxt, JsonToken t)
    throws IOException
  {
    final Object bean = _valueInstantiator.createUsingDefault(ctxt);
    // [databind#631]: Assign current value, to be accessible by custom serializers
    p.setCurrentValue(bean);
    for (; t == JsonToken.FIELD_NAME; t = p.nextToken()) {
      String propName = p.getCurrentName();
      p.nextToken();
      if (!_beanProperties.findDeserializeAndSet(p, ctxt, bean, propName)) {
        handleUnknownVanilla(p, ctxt, bean, propName);
      }
    }
    return bean;
  }

    /**
   * Convenience method that tries to find property with given name, and
   * if it is found, call {@link SettableBeanProperty#deserializeAndSet}
   * on it, and return true; or, if not found, return false.
   * Note, too, that if deserialization is attempted, possible exceptions
   * are wrapped if and as necessary, so caller need not handle those.
   * 
   * @since 2.5
   */
  public boolean findDeserializeAndSet(JsonParser p, DeserializationContext ctxt,
      Object bean, String key) throws IOException
  {
    if (_caseInsensitive) {
      key = key.toLowerCase();
    }
    int index = key.hashCode() & _hashMask;
    Bucket bucket = _buckets[index];
    // Let's unroll first lookup since that is null or match in 90+% cases
    if (bucket == null) {
      return false;
    }
    // Primarily we do just identity comparison as keys should be interned
    if (bucket.key == key) {
      try {
        bucket.value.deserializeAndSet(p, ctxt, bean);
      } catch (Exception e) {
        wrapAndThrow(e, bean, key, ctxt);
      }
      return true;
    } 
    return _findDeserializeAndSet2(p, ctxt, bean, key, index);
  }

MethodProperty
  @Override
  public void deserializeAndSet(JsonParser jp, DeserializationContext ctxt,
      Object instance) throws IOException
  {
    Object value = deserialize(jp, ctxt);
    try {
     //将得到的结果放入反序列化对应的对象中
      _setter.invoke(instance, value);
    } catch (Exception e) {
      _throwAsIOE(e, value);
    }
  }

 public final Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
  {
    JsonToken t = p.getCurrentToken();
    if (t == JsonToken.VALUE_NULL) {
      return (_nullProvider == null) ? null : _nullProvider.nullValue(ctxt);
    }
    if (_valueTypeDeserializer != null) {
      return _valueDeserializer.deserializeWithType(p, ctxt, _valueTypeDeserializer);
    }
    return _valueDeserializer.deserialize(p, ctxt);
  }
  //如果继承了JsonDeserializer类重写了deseriakize方法，则会跳转到对应注入的类中进行处理
  //不出意外的话最后都会调用 DeserializationContext的readValue(JsonParser p, Class<T> type)方法，然后会根据type的类型跳转到对应的反序列化类中进行处理。

public <T> T readValue(JsonParser p, Class<T> type) throws IOException {
    return readValue(p, getTypeFactory().constructType(type));
  }
  @SuppressWarnings("unchecked")
  public <T> T readValue(JsonParser p, JavaType type) throws IOException {
   //得到最终解析的类型，Map list string。。。。
    JsonDeserializer<Object> deser = findRootValueDeserializer(type);
    if (deser == null) {
    }
    return (T) deser.deserialize(p, this);
  }
  //例如这里如果是一个map，则会调用MapDeserializer的deserizlize方法得到最后的返回结果。
  //对于集合类，会通过token按照顺序解析生成一个个的集合对象并放入集合中。
JsonToken t;
    while ((t = p.nextToken()) != JsonToken.END_ARRAY) {
      try {
        Object value;
        if (t == JsonToken.VALUE_NULL) {
          value = valueDes.getNullValue();
        } else if (typeDeser == null) {
          value = valueDes.deserialize(p, ctxt);
        } else {
          value = valueDes.deserializeWithType(p, ctxt, typeDeser);
        }
        if (referringAccumulator != null) {
          referringAccumulator.add(value);
        } else {
          result.add(value);
        }
      } catch (UnresolvedForwardReference reference) {
        if (referringAccumulator == null) {
          throw JsonMappingException
              .from(p, "Unresolved forward reference but no identity info", reference);
        }
        Referring ref = referringAccumulator.handleUnresolvedReference(reference);
        reference.getRoid().appendReferring(ref);
      } catch (Exception e) {
        throw JsonMappingException.wrapWithPath(e, result, result.size());
      }
    }
    return result;

package com.string;
import java.util.Map;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
public class Comment {
  public String id;
  @JsonDeserialize(using = ImgPackSerializer.class)
  public Map<String, String> imgPack;
  @JsonDeserialize(using = CoopSerializer.class)
  public Coop coop;
  public Coop getCoop() {
    return coop;
  }
  public void setCoop(Coop coop) {
    this.coop = coop;
  }
  public Map<String, String> getImgPack() {
    return imgPack;
  }
  public void setImgPack(Map<String, String> imgPack) {
    this.imgPack = imgPack;
  }
  public String getId() {
    return id;
  }
  public void setId(String id) {
    this.id = id;
  }
}
class Coop {
  public Integer age;
  public Integer getAge() {
    return age;
  }
  public void setAge(Integer age) {
    this.age = age;
  }
}

package com.string;
import java.io.IOException;
import java.util.List;
import java.util.Map;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.ObjectMapper;
public class TestJson {
  static ObjectMapper OBJECT_MAPPER = new ObjectMapper();

  public static void main(String[] args) {
    String s = "{"code":"1","comm":[{"imgPack":{"abc":"abc"},"coop":[]}],"name":"car"}";
    try {
      Response readValue = OBJECT_MAPPER.readValue(s, Response.class);
      System.err.println(readValue.toString());
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}
class Response {
  public String code;
  public List<Comment> comm;
  public String name;

  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public String getCode() {
    return code;
  }
  public void setCode(String code) {
    this.code = code;
  }
  public List<Comment> getComm() {
    return comm;
  }
  public void setComm(List<Comment> comm) {
    this.comm = comm;
  }
}
class CoopSerializer extends JsonDeserializer<Coop> {
  @Override
  public Coop deserialize(JsonParser jp, DeserializationContext ctxt)
      throws IOException, JsonProcessingException {
    JsonToken currentToken = jp.getCurrentToken();
    if (currentToken == JsonToken.START_ARRAY) {
      // return null; //error may create more object
      // jp.nextToken(); //error
      return ctxt.readValue(jp, Object.class) == null ? null : null;
    } else if (currentToken == JsonToken.START_OBJECT) {
      return (Coop) ctxt.readValue(jp, Coop.class);
    }
    return null;
  }
}
class ImgPackSerializer extends JsonDeserializer<Map<String, String>> {
  @Override
  public Map<String, String> deserialize(JsonParser jp,
      DeserializationContext ctxt) throws IOException,
      JsonProcessingException {
    JsonToken currentToken = jp.getCurrentToken();
    if (currentToken == JsonToken.START_ARRAY) {
      return ctxt.readValue(jp, Object.class) == null ? null : null;
    } else if (currentToken == JsonToken.START_OBJECT) {
      return (Map<String, String>) ctxt.readValue(jp, Map.class);
    }
    return null;
  }
}