ProtocolProcessor
配合@ByteBufValidation, @ByteBufConvert, @Protocol, @CacheMapping等注解
基于模板注解设计模式以及Javac提供的Annotation-processor-util技术(编译前类文件的语法树处理),
实现协议的Decode/Encode
以下是引用protocol-codec-manager项目的mqtt3.0#connect报文示例
@Data
@ByteBufValidation(
validate = @ByteBufValidation.Validate(
index = @ByteBufInternalPoint(step = "1"),
length = @ByteBufInternalPoint(step = "4")
),
mapper = @ByteBufValidation.Mapper(
index = @ByteBufInternalPoint(step = "1"),
length = @ByteBufInternalPoint(step = "4")
),
validateMethod = MqttPacketLengthValidateMethod.class
)
public abstract class AbstractMqttCommand {
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = BinaryIntegerConvertMethod.class,
parameters = {"0", "4"}
)
private Integer packetType;
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "-1"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = BinaryIntegerConvertMethod.class,
parameters = {"4", "7"}
)
private Integer packetTypeSign;
/** 这里直接传默认最大长度4字节 */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(step = "4"),
convertMethod = MqttPacketLengthConvertMethod.class
)
private Integer packetLength = 0xffffff7f;
}
---------------------------------- ----------------------------------
@Data
@EqualsAndHashCode(callSuper = true)
@CacheMapping("mqttConnectCommand")
public class MqttConnectCommand extends AbstractMqttCommand {
/* ******************************** 可变报文头部 固定10字节 ********************************/
/** 协议名不正确的情况下, 不处理connect报文, 防火墙可以根据该字段来识别mqtt流量 */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "2"),
length = @ByteBufInternalPoint(step = "4"),
convertMethod = Utf8ConvertMethod.class
)
private String protocolName = "MQTT";
/** 如果不支持该协议级别, 在connAck报文中响应返回码0x01, 并断开客户端连接 */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = IntegerConvertMethod.class
)
private Integer protocolLevel = 4;
/** 如果connect控制报文的保留标志位不为0, 直接断开客户端连接 */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = BinaryIntegerConvertMethod.class,
parameters = {"7", "8"}
)
private Integer reserved = 0;
/** 清理会话, 指定了会话状态的处理方式, 这个标志位控制会话状态的生存时间 */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "-1"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = BinaryIntegerConvertMethod.class,
parameters = {"6", "7"}
)
private Integer cleanSession;
/**
* 遗嘱标志, 如果设置为1， 表示如果连接请求被接受了，willQoS消息必须存储在服务端并且与这个网络连接关联.
* 并且在网络连接关闭时, 服务端必须发布这个遗嘱信息, 除非服务端收到disconnect报文并删除了这个遗嘱信息
*/
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "-1"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = BinaryIntegerConvertMethod.class,
parameters = {"5", "6"}
)
private Integer willFlag;
/** 遗嘱QoS */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "-1"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = BinaryIntegerConvertMethod.class,
parameters = {"3", "5"}
)
private Integer willQoS;
/** 遗嘱保留 */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "-1"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = BinaryIntegerConvertMethod.class,
parameters = {"2", "3"}
)
private Integer willRetain;
/** 密码标志 */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "-1"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = BinaryIntegerConvertMethod.class,
parameters = {"1", "2"}
)
private Integer passwordFlag;
/** 用户名标志 */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "-1"),
length = @ByteBufInternalPoint(step = "1"),
convertMethod = BinaryIntegerConvertMethod.class,
parameters = {"0", "1"}
)
private Integer userNameFlag;
/** 保持连接时间 */
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(step = "2"),
convertMethod = IntegerConvertMethod.class
)
private Integer keepAliveTime;
/* ******************************** PayLoad ********************************/
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(step = "2"),
convertMethod = IntegerConvertMethod.class
)
private Integer clientIdLength;
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "clientIdLength", keyClazz = MqttConnectCommand.class),
type = ByteBufInternalPoint.StepType.MODEL
),
convertMethod = Utf8ConvertMethod.class
)
private String clientId;
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(step = "2"),
convertMethod = IntegerConvertMethod.class,
condition = @ByteBufInternalCondition(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "willFlag", keyClazz = MqttConnectCommand.class),
compareValue = "1"
)
)
private Integer willTopicLength;
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "willTopicLength", keyClazz = MqttConnectCommand.class),
type = ByteBufInternalPoint.StepType.MODEL
),
convertMethod = Utf8ConvertMethod.class,
condition = @ByteBufInternalCondition(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "willFlag", keyClazz = MqttConnectCommand.class),
compareValue = "1"
)
)
private String willTopic;
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(step = "2"),
convertMethod = IntegerConvertMethod.class,
condition = @ByteBufInternalCondition(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "userNameFlag", keyClazz = MqttConnectCommand.class),
compareValue = "1"
)
)
private Integer useNameLength;
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "useNameLength", keyClazz = MqttConnectCommand.class),
type = ByteBufInternalPoint.StepType.MODEL
),
convertMethod = Utf8ConvertMethod.class,
condition = @ByteBufInternalCondition(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "userNameFlag", keyClazz = MqttConnectCommand.class),
compareValue = "1"
)
)
private String userName;
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(step = "2"),
convertMethod = IntegerConvertMethod.class,
condition = @ByteBufInternalCondition(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "passwordFlag", keyClazz = MqttConnectCommand.class),
compareValue = "1"
)
)
private Integer passwordLength;
@ByteBufConvert(
index = @ByteBufInternalPoint(step = "0"),
length = @ByteBufInternalPoint(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "passwordLength", keyClazz = MqttConnectCommand.class),
type = ByteBufInternalPoint.StepType.MODEL
),
convertMethod = Utf8ConvertMethod.class,
condition = @ByteBufInternalCondition(model = @ByteBufInternalModel(
key = "mqttConnectCommand", prop = "passwordFlag", keyClazz = MqttConnectCommand.class),
compareValue = "1"
)
)
private String password;
}@Protocol(implName = "MqttParserImpl")
public interface MqttParser {
@ByteBufEncode(initialCapacity = 2 << 7)
ByteBuf encode(MqttConnectCommand command, Channel channel);
@ByteBufDecode()
MqttConnectCommand decode(ByteBuf buffer, Channel channel);
}这里说明以下不使用JavaPoet依赖的原因, 当模板内容过于复杂(嵌套, 多重策略等), 建议还是模板与代码分离, 便于阅读和维护. 这里内部使用freemarker作为模板依赖, 参考了mapStruct的源码. 更多详情参考protocol-codec-manager项目...
之前有想法对guava包的eventbus做apt改造的, 但经思考本地订阅策略并不实用, 还需要维护对应的topic, 就没继续开发了.
有好的想法或者建议, 可以提issue, 多谢.