问题1：
反序列化的枚举类：
@Message public enum EnumClassd { Unknown (0); @Getter @Setter private Integer code; EnumClassd(Integer code) { this.code = code; } }
MessagePack反序列化上述枚举类时报错：
org.msgpack.MessageTypeException: org.msgpack.template.builder.TemplateBuildException: Cannot compile: { if (!$3 && $1.trySkipNil()) { return null; } com.example.EnumClass _$$_t; if ($2 == null) { _$$_t = new com.example.EnumClass(); } else { _$$_t = (com.example.EnumClass) $2; } $1.readArrayBegin(); if ($1.trySkipNil()) { } else { org.msgpack.template.builder.DefaultBuildContext.readPrivateField($1, _$$_t, com.example.EnumClass.class, "code", templates[0]); } $1.readArrayEnd(); return _$$_t; } at org.msgpack.template.TemplateRegistry.buildAndRegister(TemplateRegistry.java:575) at org.msgpack.template.TemplateRegistry.lookupAfterBuilding(TemplateRegistry.java:472) at org.msgpack.template.TemplateRegistry.lookup(TemplateRegistry.java:251) at org.msgpack.template.builder.JavassistTemplateBuilder.toTemplate(JavassistTemplateBuilder.java:129) at org.msgpack.template.builder.JavassistTemplateBuilder.buildTemplate(JavassistTemplateBuilder.java:117) at org.msgpack.template.builder.AbstractTemplateBuilder.buildTemplate(AbstractTemplateBuilder.java:61) at org.msgpack.template.TemplateRegistry.buildAndRegister(TemplateRegistry.java:562) at org.msgpack.template.TemplateRegistry.lookupAfterBuilding(TemplateRegistry.java:472) at org.msgpack.template.TemplateRegistry.lookup(TemplateRegistry.java:251) at org.msgpack.template.TemplateRegistry.lookupGenericTypeImpl0(TemplateRegistry.java:320) at org.msgpack.template.TemplateRegistry.lookupGenericTypeImpl(TemplateRegistry.java:308) at org.msgpack.template.TemplateRegistry.lookupGenericType(TemplateRegistry.java:280) at org.msgpack.template.TemplateRegistry.lookup(TemplateRegistry.java:205) at org.msgpack.template.builder.JavassistTemplateBuilder.toTemplate(JavassistTemplateBuilder.java:129) at org.msgpack.template.builder.JavassistTemplateBuilder.buildTemplate(JavassistTemplateBuilder.java:117) at org.msgpack.template.builder.AbstractTemplateBuilder.buildTemplate(AbstractTemplateBuilder.java:61) at org.msgpack.template.TemplateRegistry.buildAndRegister(TemplateRegistry.java:562) at org.msgpack.template.TemplateRegistry.lookupAfterBuilding(TemplateRegistry.java:472) at org.msgpack.template.TemplateRegistry.lookup(TemplateRegistry.java:251) at org.msgpack.MessagePack.read(MessagePack.java:370) at com.example.jenkinscodehubtest.util.OsvfUtil.ReadNextBlock(OsvfUtil.java:61) at com.example.jenkinscodehubtest.JenkinsCodehubTestApplicationTests.deal(JenkinsCodehubTestApplicationTests.java:46) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688) at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60) at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131) at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149) at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140) at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84) at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115) at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105) at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106) at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64) at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45) at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37) at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104) at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129) at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126) at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84) at java.util.ArrayList.forEach(ArrayList.java:1249) at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129) at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126) at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84) at java.util.ArrayList.forEach(ArrayList.java:1249) at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129) at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126) at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84) at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32) at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57) at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52) at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96) at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75) at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53) Caused by: org.msgpack.template.builder.TemplateBuildException: Cannot compile: { if (!$3 && $1.trySkipNil()) { return null; } com.example.EnumClass _$$_t; if ($2 == null) { _$$_t = new com.example.EnumClass(); } else { _$$_t = (com.example.EnumClass) $2; } $1.readArrayBegin(); if ($1.trySkipNil()) { } else { org.msgpack.template.builder.DefaultBuildContext.readPrivateField($1, _$$_t, com.example.EnumClass.class, "code", templates[0]); } $1.readArrayEnd(); return _$$_t; } at org.msgpack.template.builder.BuildContext.build(BuildContext.java:73) at org.msgpack.template.builder.DefaultBuildContext.buildTemplate(DefaultBuildContext.java:56) at org.msgpack.template.builder.JavassistTemplateBuilder.buildTemplate(JavassistTemplateBuilder.java:119) at org.msgpack.template.builder.AbstractTemplateBuilder.buildTemplate(AbstractTemplateBuilder.java:61) at org.msgpack.template.TemplateRegistry.buildAndRegister(TemplateRegistry.java:562) ... 86 more Caused by: javassist.CannotCompileException: [source error] no such constructor: com.example.EnumClass at javassist.CtBehavior.setBody(CtBehavior.java:446) at javassist.CtBehavior.setBody(CtBehavior.java:412) at javassist.CtNewMethod.make(CtNewMethod.java:138) at org.msgpack.template.builder.BuildContext.buildReadMethod(BuildContext.java:144) at org.msgpack.template.builder.BuildContext.build(BuildContext.java:65) ... 90 more Caused by: compile error: no such constructor: com.example.EnumClass at javassist.compiler.MemberCodeGen.atMethodCallCore2(MemberCodeGen.java:593) at javassist.compiler.MemberCodeGen.atMethodCallCore(MemberCodeGen.java:575) at javassist.compiler.MemberCodeGen.atNewExpr(MemberCodeGen.java:302) at javassist.compiler.ast.NewExpr.accept(NewExpr.java:73) at javassist.compiler.CodeGen.atAssignCore(CodeGen.java:860) at javassist.compiler.CodeGen.atVariableAssign(CodeGen.java:793) at javassist.compiler.CodeGen.atAssignExpr(CodeGen.java:747) at javassist.compiler.CodeGen.atStmnt(CodeGen.java:332) at javassist.compiler.ast.Stmnt.accept(Stmnt.java:50) at javassist.compiler.CodeGen.atStmnt(CodeGen.java:351) at javassist.compiler.ast.Stmnt.accept(Stmnt.java:50) at javassist.compiler.CodeGen.atIfStmnt(CodeGen.java:391) at javassist.compiler.CodeGen.atStmnt(CodeGen.java:355) at javassist.compiler.ast.Stmnt.accept(Stmnt.java:50) at javassist.compiler.CodeGen.atStmnt(CodeGen.java:351) at javassist.compiler.ast.Stmnt.accept(Stmnt.java:50) at javassist.compiler.CodeGen.atMethodBody(CodeGen.java:292) at javassist.compiler.Javac.compileBody(Javac.java:223) at javassist.CtBehavior.setBody(CtBehavior.java:438) ... 94 more Disconnected from the target VM, address: '127.0.0.1:54789', transport: 'socket' Process finished with exit code -1
解决方法：
将注解@Message改为注解@MessagePackOrdinalEnum即可解决(https://github.com/msgpack/msgpack/issues/66)
问题2：
Exception in thread "main" org.msgpack.MessageTypeException: Expected raw value, but got boolean at org.msgpack.unpacker.Accept.acceptBoolean(Accept.java:33) at org.msgpack.unpacker.MessagePackUnpacker.readOneWithoutStackLarge(MessagePackUnpacker.java:154) at org.msgpack.unpacker.MessagePackUnpacker.readOneWithoutStack(MessagePackUnpacker.java:139) at org.msgpack.unpacker.MessagePackUnpacker.readOne(MessagePackUnpacker.java:73) at org.msgpack.unpacker.MessagePackUnpacker.readString(MessagePackUnpacker.java:502) at org.msgpack.template.StringTemplate.read(StringTemplate.java:46) at org.msgpack.template.StringTemplate.read(StringTemplate.java:25) at org.msgpack.template.AbstractTemplate.read(AbstractTemplate.java:31) at com.my.msgpack.SimpleMessagePackPractice$MyMessage2_$$_Template_1305193908_1.read(SimpleMessagePackPractice$MyMessage2_$$_Template_1305193908_1.java) at org.msgpack.template.AbstractTemplate.read(AbstractTemplate.java:31) at org.msgpack.MessagePack.read(MessagePack.java:388) at org.msgpack.MessagePack.read(MessagePack.java:371) at com.my.msgpack.SimpleMessagePackPractice.main(SimpleMessagePackPractice.java:61)
该报错是因为MessagePack序列化的结果中只包含了value，而不包含key。因而在进行反序列化需要保证类中属性的顺序必须保证完全一致，否则就会出错：
如果两个属性的类型一致，可以反序列化，但是值发生错乱。
如果两个属性的类型不一致，会抛出类型不匹配异常。
因此解决方法是报错序列化和反序列化的对象顺序类型保持一致。
MessagePack详情见下文：
一、MessagePack是什么
先看官方的定义：MessagePack是一种高效的二进制序列化格式。它允许您像JSON一样在多个语言之间交换数据。但是，它更快并且更小。
从官方定义中，可以有如下的结论：
-
MessagePack是一个二进制序列化格式，因而它序列化的结果可以在多个语言间进行数据的交换。
-
从性能上讲，它要比json的序列化格式要好。
-
从结果大小上讲，它要比json的序列化结果要小。
但是官方并没有提MessagePack和google pb的对比，实际上从空间和时间两个方面对比，pb均要优于MessagePack，但pb相对MessagePack 的缺点是支持的语言种类比较少，需要编写专门的 .proto文件，使用上没有MessagePack方便。
二、MessagePack的主要概念
2.1 type system
类型体系是MessagePack的基础，也是MessagePack在序列化后比json占用空间小的关键。当前包含的type有如下几类：
-
Integer represents an integer
-
Nil represents nil
-
Boolean represents true or false
-
Float represents a IEEE 754 double precision floating point number including NaN and Infinity
-
Raw
-
String extending Raw type represents a UTF-8 string
-
Binary extending Raw type represents a byte array
-
-
Array represents a sequence of objects
-
Map represents key-value pairs of objects
-
Extension represents a tuple of type information and a byte array where type information is an integer whose meaning is defined by applications or MessagePack specification
-
Timestamp represents an instantaneous point on the time-line in the world that is independent from time zones or calendars. Maximum precision is nanoseconds.
-
这个类型体系将我们在代码开发中用到的数据格式进行了映射，并且通过Extension这个类型给使用者留出了自由扩充的空间，但由于表示形式的限制，当前Extension最多有127个。
每一种类型能够表示的范围可以查看MessagePack规范中的Limitation部分和Extension types部分。
2.2 formats
在MessagePack中一个value的组成格式是这样的：类型[长度][data]。下面列出几个示例，详细完整的描述请看附录中的MessagePack规范。
2.2.1常量型
比如对于null、true、false这三个值，在MessagePack会被固定的映射为如下的值。
|
format name
|
first byte (in binary)
|
first byte (in hex)
|
|
nil
|
11000000
|
0xc0
|
|
false
|
11000010
|
0xc2
|
|
true
|
11000011
|
0xc3
|
2.2.2 int型（包含有符号整数和无符号整数）
示例如下
-
0xcc表示当前的值的类型是无符号整数并且长度不超过8个bit，具体的值内容需要通过后续8个bit位的内容来计算
-
0xcd表示当前的值的类型是无符号整数并且长度不超过16个bit，具体的值内容需要通过后续16个bit位的内容来计算
-
0xd0表示当前的值的类型是有符号整数并且长度不超过8个bit，具体的值内容需要通过后续8个bit位的内容来计算
-
0xd1表示当前的值的类型是有符号整数并且长度不超过16个bit，具体的值内容需要通过后续16个bit位的内容来计算
uint 8 stores a 8-bit unsigned integer +--------+--------+ | 0xcc |ZZZZZZZZ| +--------+--------+ uint 16 stores a 16-bit big-endian unsigned integer +--------+--------+--------+ | 0xcd |ZZZZZZZZ|ZZZZZZZZ| +--------+--------+--------+ int 8 stores a 8-bit signed integer +--------+--------+ | 0xd0 |ZZZZZZZZ| +--------+--------+ int 16 stores a 16-bit big-endian signed integer +--------+--------+--------+ | 0xd1 |ZZZZZZZZ|ZZZZZZZZ| +--------+--------+--------+
2.2.3 字符串
-
0xd9表示当前的值的类型是字符串并且长度不超过(2^8)-1个bytes ，具体的长度需要通过后续8个bit位的内容来计算，字符串的具体内容是后续长度的byte所表示的内容
-
0xda表示当前的值的类型是字符串并且长度不超过(2^16)-1个bytes ，具体的长度需要通过后续16个bit位的内容来计算，字符串的具体内容是后续长度的byte所表示的内容
str 8 stores a byte array whose length is upto (2^8)-1 bytes: +--------+--------+========+ | 0xd9 |YYYYYYYY| data | +--------+--------+========+ str 16 stores a byte array whose length is upto (2^16)-1 bytes: +--------+--------+--------+========+ | 0xda |ZZZZZZZZ|ZZZZZZZZ| data | +--------+--------+--------+========+
2.2.4 数组
-
0xdc表示当前的值的类型是数组并且长度不超过(2^16)-1个元素 ，具体的长度需要通过后续16个bit位（两个byte）的内容来计算，计算出来的值就是数组元素的个数
-
0xdd表示当前的值的类型是数组并且长度不超过(2^32)-1个元素 ，具体的长度需要通过后续32个bit位（4个byte）的内容来计算，计算出来的值就是数组元素的个数
array 16 stores an array whose length is upto (2^16)-1 elements: +--------+--------+--------+~~~~~~~~~~~~~~~~~+ | 0xdc |YYYYYYYY|YYYYYYYY| N objects | +--------+--------+--------+~~~~~~~~~~~~~~~~~+ array 32 stores an array whose length is upto (2^32)-1 elements: +--------+--------+--------+--------+--------+~~~~~~~~~~~~~~~~~+ | 0xdd |ZZZZZZZZ|ZZZZZZZZ|ZZZZZZZZ|ZZZZZZZZ| N objects | +--------+--------+--------+--------+--------+~~~~~~~~~~~~~~~~~+
2.2.5 小结
2.3 Serialization：type to format conversion
|
source types
|
output format
|
|
Integer
|
int format family (positive fixint, negative fixint, int 8/16/32/64 or uint 8/16/32/64)
|
|
Nil
|
nil
|
|
Boolean
|
bool format family (false or true)
|
|
Float
|
float format family (float 32/64)
|
|
String
|
str format family (fixstr or str 8/16/32)
|
|
Binary
|
bin format family (bin 8/16/32)
|
|
Array
|
array format family (fixarray or array 16/32)
|
|
Map
|
map format family (fixmap or map 16/32)
|
|
Extension
|
ext format family (fixext or ext 8/16/32)
|
If an object can be represented in multiple possible output formats, serializers SHOULD use the format which represents the data in the smallest number of bytes.
2.4 Deserialization: format to type conversion
|
source formats
|
output type
|
|
positive fixint, negative fixint, int 8/16/32/64 and uint 8/16/32/64
|
Integer
|
|
nil
|
Nil
|
|
false and true
|
Boolean
|
|
float 32/64
|
Float
|
|
fixstr and str 8/16/32
|
String
|
|
bin 8/16/32
|
Binary
|
|
fixarray and array 16/32
|
Array
|
|
fixmap map 16/32
|
Map
|
|
fixext and ext 8/16/32
|
Extension
|
三、为什么MessagePack比json序列化使用的字节流更少
3.1 直观对比
可以通过下图的两张图简单进行下对比，第一张图是同一个数据类型的内容用json和messagepack序列化的结果。
从第二张图可以明显看到messagepack要比json占用的空间更少。
3.2 序列化结果只有value且value进行了专属映射
这张图是MessagePack官网上的，用来进行json和MessagePack序列化结果的对比，实际情况是否确实如此呢？
我本地使用的msgpack-0.6.12版本。
代码如下：
public class MessagePackSerializationCompareJson { @Message // Annotation public static class MyMessage { // public fields are serialized. public boolean compact; public int schema; public String toString() { return "compact:"+compact+";schema:"+schema; } } /** * * @param args * @throws IOException */ public static void main(String[] args) throws IOException { //初始化一个对象 MyMessage src = new MyMessage(); src.compact = true; src.schema=0; //利用MessagePack进行序列化 MessagePack msgpack = new MessagePack(); // Serialize byte[] bytes = msgpack.write(src); System.out.println("msgpack result length:"+bytes.length); //利用json进行序列化 String jsonResult = JSONObject.toJSON(src).toString(); System.out.println("json result length:"+jsonResult.getBytes().length); } }
运行结果如下：
json result length:27
msgpack result length:3
json序列化的结果是27，和官网图片中的结果相同。但MessagePack的序列化结果是3，要比官网中的数字小很多。
按照上面图片的解释应当是：
-
第一个byte是82，表示序列化后的结果有两个元素
-
第二个byte是c3，表示第一个元素的值是true
-
第三个byte是00，表示第二个元素的值是0
为了验证我们的推测，我们可以在MyMessage类中再添加一个boolean类型的属性，但不给这个属性赋值，按照java的规范，这个属性的值就是false，按照MessagePack的规范，就会被转为一个byte的c2，这样msgpack序列化后的长度值就是4. 而json序列化的增加值要增加不少，是属性名称的长度+5（false的长度）+4（要增加两个双引号，一个逗号，一个冒号），如果属性名称长度是4，则一共会增加13个byte，总长度就是40.
public class MessagePackSerializationCompareJson { @Message // Annotation public static class MyMessage { // public fields are serialized. public boolean compact; public int schema; public boolean link; public String toString() { return "compact:"+compact+";schema:"+schema+";link:"+link; } } /** * * @param args * @throws IOException */ public static void main(String[] args) throws IOException { //初始化一个对象 MyMessage src = new MyMessage(); src.compact = true; src.schema=0; //利用json进行序列化 String jsonResult = JSONObject.toJSON(src).toString(); System.out.println("json result length:"+jsonResult.getBytes().length); //利用MessagePack进行序列化 MessagePack msgpack = new MessagePack(); // Serialize byte[] bytes = msgpack.write(src); System.out.println("msgpack result length:"+bytes.length); } }
上面代码的执行的结果也符合猜测：
json result length:40
msgpack result length:4
从这个数字上看，MessagePack明显优于json，特别是在属性多的情况下差距会更大。即使json中把key去掉，序列化后的结果也要比MessagePack占用的空间大。
3.2 序列化对象的属性顺序不能变动
3.1分析了MessagePack序列化的结果中只包含了value，而不包含key。因而在进行反序列化需要保证类中属性的顺序必须保证完全一致，否则就会出错：
如果两个属性的类型一致，可以反序列化，但是值发生错乱。
如果两个属性的类型不一致，会抛出类型不匹配异常。
3.2.1 顺序不同，类型相同
public class SimpleMessagePackPractice { @Message // Annotation public static class MyMessage { // public fields are serialized. public boolean compact; public boolean link; public String toString() { return "link:" + link + ";compact:" + compact; } } @Message // Annotation public static class MyMessage2 { // public fields are serialized. public boolean link; public boolean compact; public String toString() { return "link:" + link + ";compact:" + compact; } } /** * * @param args * @throws IOException */ public static void main(String[] args) throws IOException { //初始化一个对象 MyMessage src = new MyMessage(); src.compact = true; src.link = false; //利用MessagePack进行序列化 MessagePack msgpack = new MessagePack(); // Serialize byte[] bytes = msgpack.write(src); //利用MessagePack进行反序列化 MyMessage2 dst = msgpack.read(bytes, MyMessage2.class); System.out.println("msgpack 原始数据:" + src); System.out.println("msgpack 反序列化:" + dst); } }
上述代码的执行结果如下：
msgpack 原始数据:link:false;compact:true msgpack 反序列化:link:true;compact:false
3.2.1 顺序不同，类型不同
public class SimpleMessagePackPractice { @Message // Annotation public static class MyMessage { // public fields are serialized. public boolean compact; public String link; public String toString() { return "link:" + link + ";compact:" + compact; } } @Message // Annotation public static class MyMessage2 { // public fields are serialized. public String link; public boolean compact; public String toString() { return "link:" + link + ";compact:" + compact; } } /** * * @param args * @throws IOException */ public static void main(String[] args) throws IOException { //初始化一个对象 MyMessage src = new MyMessage(); src.compact = true; src.link = "www.baidu.com"; //利用MessagePack进行序列化 MessagePack msgpack = new MessagePack(); // Serialize byte[] bytes = msgpack.write(src); //利用MessagePack进行反序列化 MyMessage2 dst = msgpack.read(bytes, MyMessage2.class); System.out.println("msgpack 原始数据:" + src); System.out.println("msgpack 反序列化:" + dst); } }
执行结果：
Exception in thread "main" org.msgpack.MessageTypeException: Expected raw value, but got boolean at org.msgpack.unpacker.Accept.acceptBoolean(Accept.java:33) at org.msgpack.unpacker.MessagePackUnpacker.readOneWithoutStackLarge(MessagePackUnpacker.java:154) at org.msgpack.unpacker.MessagePackUnpacker.readOneWithoutStack(MessagePackUnpacker.java:139) at org.msgpack.unpacker.MessagePackUnpacker.readOne(MessagePackUnpacker.java:73) at org.msgpack.unpacker.MessagePackUnpacker.readString(MessagePackUnpacker.java:502) at org.msgpack.template.StringTemplate.read(StringTemplate.java:46) at org.msgpack.template.StringTemplate.read(StringTemplate.java:25) at org.msgpack.template.AbstractTemplate.read(AbstractTemplate.java:31) at com.my.msgpack.SimpleMessagePackPractice$MyMessage2_$$_Template_1305193908_1.read(SimpleMessagePackPractice$MyMessage2_$$_Template_1305193908_1.java) at org.msgpack.template.AbstractTemplate.read(AbstractTemplate.java:31) at org.msgpack.MessagePack.read(MessagePack.java:388) at org.msgpack.MessagePack.read(MessagePack.java:371) at com.my.msgpack.SimpleMessagePackPractice.main(SimpleMessagePackPractice.java:61)