1 、使用bytebuf填充
public class UgvData implements Serializible{
private static final long serialVersionUID = -219988432063763456L;
//状态码
byte status;
public byte[] toByteArray() {
ByteBuf buf = Unpooled.buffer(32);
buf.writeByte(this.getStatus());
return buf.array();
}
//省略get set
}
2、使用json包含的方法
JSON.toJsonString(Data).getBytes()
3、反射的方式
第一种方法的缺点在于，每一个类都要这么写一个toByteArray方法。如果类多了是非常麻烦的。有什么方便的方法吗？当然是有的，利用反射的方式（只会在第一次反射，后面会做本地缓存，所以性能开销不大）。需要在一个文件夹下添加下面五个类
1: Codecable
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.google.common.collect.Lists;
import lombok.Data;
import java.lang.reflect.Field;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
@Data
public abstract class Codecable {
public static List
resolveFileldWrapperList(Class clazz){ Field[] fields = clazz.getDeclaredFields();
List
fieldWrapperList = Lists.newArrayList(); for (Field field : fields) {
CodecProprety codecProprety = field.getAnnotation(CodecProprety.class);
if (codecProprety == null) {
continue;
}
FieldWrapper fw = new FieldWrapper(field, codecProprety);
fieldWrapperList.add(fw);
}
Collections.sort(fieldWrapperList, new Comparator
() { @Override
public int compare(FieldWrapper o1, FieldWrapper o2) {
return o1.getCodecProprety().order() - o2.getCodecProprety().order();
}
});
return fieldWrapperList;
}
@JsonIgnore
public abstract List
getFieldWrapperList(); }
2: CodecProprety
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD})
public @interface CodecProprety {
/**
* 属性顺序
* @return
*/
int order();
/**
* 数据长度。解码时用，除了简单数据类型之外才起作用（如：String）。
* @return
*/
int length() default 0;
}
3: FieldWrapper
import lombok.AllArgsConstructor;
import lombok.Data;
import java.lang.reflect.Field;
@Data
@AllArgsConstructor
public class FieldWrapper {
/**
* 上下行数据属性
*/
private Field field;
/**
* 上下行数据属性上的注解
*/
private CodecProprety codecProprety;
}
4: PayloadDecoder
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.nio.charset.Charset;
import java.util.List;
public class PayloadDecoder {
public static
T resolve(byte[] src, Class clazz) { T instance = null;
try {
instance = clazz.newInstance();
} catch (Exception e) {
throw new RuntimeException("实例化类失败", e);
}
List
fieldWrapperList = instance.getFieldWrapperList(); ByteBuf buffer = Unpooled.buffer().writeBytes(src);
for (FieldWrapper fieldWrapper : fieldWrapperList) {
fillData(fieldWrapper, instance, buffer);
}
return instance;
}
private static void fillData(FieldWrapper fieldWrapper, Object instance, ByteBuf buffer) {
Field field = fieldWrapper.getField();
field.setAccessible(true);
String typeName = field.getType().getName();
try {
switch (typeName) {
case "java.lang.Boolean":
case "boolean":
boolean b = buffer.readBoolean();
field.set(instance, b);
break;
case "java.lang.Character":
case "char":
CharSequence charSequence = buffer.readCharSequence(fieldWrapper.getCodecProprety().length(), Charset.forName("UTF-8"));
field.set(instance, charSequence);
break;
case "java.lang.Byte":
case "byte":
byte b1 = buffer.readByte();
field.set(instance, b1);
break;
case "java.lang.Short":
case "short":
short readShort = buffer.readShort();
field.set(instance, readShort);
break;
case "java.lang.Integer":
case "int":
int readInt = buffer.readInt();
field.set(instance, readInt);
break;
case "java.lang.Long":
case "long":
long l = buffer.readLong();
field.set(instance, l);
break;
case "java.lang.Float":
case "float":
float readFloat = buffer.readFloat();
field.set(instance, readFloat);
break;
case "java.lang.Double":
case "double":
double readDouble = buffer.readDouble();
field.set(instance, readDouble);
break;
case "java.lang.String":
String readString = buffer.readCharSequence(fieldWrapper.getCodecProprety().length(), Charset.forName("UTF-8")).toString();
field.set(instance, readString);
break;
default:
throw new RuntimeException(typeName + "不支持，bug");
}
} catch (Exception e) {
throw new RuntimeException(typeName + "读取失败，field:" + field.getName(), e);
}
}
}
5: PayloadEncoder
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.nio.charset.Charset;
import java.util.List;
public class PayloadEncoder {
public static
byte[] getPayload(T command) { List
fieldWrapperList = command.getFieldWrapperList(); ByteBuf buffer = Unpooled.buffer();
fieldWrapperList.forEach(fieldWrapper -> write2ByteBuf(fieldWrapper, command, buffer));
return buffer.array();
}
/**
* 数据写入到ByteBuf
*
* @param fieldWrapper
* @param instance
* @param buffer
*/
private static void write2ByteBuf(FieldWrapper fieldWrapper, Object instance, ByteBuf buffer) {
Field field = fieldWrapper.getField();
String typeName = field.getType().getName();
field.setAccessible(true);
Object value = null;
try {
value = field.get(instance);
} catch (IllegalAccessException e) {
new RuntimeException("反射获取值失败，filed:" + field.getName(), e);
}
switch (typeName) {
case "java.lang.Boolean":
case "boolean":
buffer.writeBoolean((Boolean) value);
break;
case "java.lang.Character":
case "char":
buffer.writeCharSequence((CharSequence) value, Charset.forName("UTF-8"));
break;
case "java.lang.Byte":
case "byte":
buffer.writeByte((byte) value);
break;
case "java.lang.Short":
case "short":
buffer.writeShort((short) value);
break;
case "java.lang.Integer":
case "int":
buffer.writeInt((int) value);
break;
case "java.lang.Long":
case "long":
buffer.writeLong((long) value);
break;
case "java.lang.Float":
case "float":
buffer.writeFloat((float) value);
break;
case "java.lang.Double":
case "double":
buffer.writeDouble((double) value);
break;
case "java.lang.String":
buffer.writeCharSequence((CharSequence) value, Charset.forName("UTF-8"));
break;
default:
throw new RuntimeException(typeName + "不支持，bug");
}
}
}
添加完上面五个类之后，使用也很简单，只需要如下所示，就可以把driveStartData转成byte数组。
PayloadEncoder.getPayload(driveStartData);
4 总结
第一种和第三种可以归为一类，都是把对象直接转成byte数组，下一层做解析的话，可以一个一个元素取；
第二种情况是把对象的json字符串转成byte数组，问题就在于，json字符串最开头是”{“，也就是转成的byte数组的第一位是”{“对应的数值
在使用中应该根据情况来，如果下一层做解析是直接取元素，对象少的话用第一种；对象多的话用第三种；
如果下一层做了排除掉json的一些格式的解析，就用第二种
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原文：https://blog.csdn.net/antony9118/article/details/80713348