問題1：
反序列化的枚舉類：
@Message public enum EnumClassd { Unknown (0); @Getter @Setter private Integer code; EnumClassd(Integer code) { this.code = code; } }
MessagePack反序列化上述枚舉類時報錯：
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
解決方法：
將注解@Message改為注解@MessagePackOrdinalEnum即可解決(https://github.com/msgpack/msgpack/issues/66)
問題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)
該報錯是因為MessagePack序列化的結果中只包含了value，而不包含key。因而在進行反序列化需要保證類中屬性的順序必須保證完全一致，否則就會出錯：
如果兩個屬性的類型一致，可以反序列化，但是值發生錯亂。
如果兩個屬性的類型不一致，會拋出類型不匹配異常。
因此解決方法是報錯序列化和反序列化的對象順序類型保持一致。
MessagePack詳情見下文：
一、MessagePack是什么
先看官方的定義：MessagePack是一種高效的二進制序列化格式。它允許您像JSON一樣在多個語言之間交換數據。但是，它更快並且更小。
從官方定義中，可以有如下的結論：
-
MessagePack是一個二進制序列化格式，因而它序列化的結果可以在多個語言間進行數據的交換。
-
從性能上講，它要比json的序列化格式要好。
-
從結果大小上講，它要比json的序列化結果要小。
但是官方並沒有提MessagePack和google pb的對比，實際上從空間和時間兩個方面對比，pb均要優於MessagePack，但pb相對MessagePack 的缺點是支持的語言種類比較少，需要編寫專門的 .proto文件，使用上沒有MessagePack方便。
二、MessagePack的主要概念
2.1 type system
類型體系是MessagePack的基礎，也是MessagePack在序列化后比json占用空間小的關鍵。當前包含的type有如下幾類：
-
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.
-
這個類型體系將我們在代碼開發中用到的數據格式進行了映射，並且通過Extension這個類型給使用者留出了自由擴充的空間，但由於表示形式的限制，當前Extension最多有127個。
每一種類型能夠表示的范圍可以查看MessagePack規范中的Limitation部分和Extension types部分。
2.2 formats
在MessagePack中一個value的組成格式是這樣的：類型[長度][data]。下面列出幾個示例，詳細完整的描述請看附錄中的MessagePack規范。
2.2.1常量型
比如對於null、true、false這三個值，在MessagePack會被固定的映射為如下的值。
|
format name
|
first byte (in binary)
|
first byte (in hex)
|
|
nil
|
11000000
|
0xc0
|
|
false
|
11000010
|
0xc2
|
|
true
|
11000011
|
0xc3
|
2.2.2 int型（包含有符號整數和無符號整數）
示例如下
-
0xcc表示當前的值的類型是無符號整數並且長度不超過8個bit，具體的值內容需要通過后續8個bit位的內容來計算
-
0xcd表示當前的值的類型是無符號整數並且長度不超過16個bit，具體的值內容需要通過后續16個bit位的內容來計算
-
0xd0表示當前的值的類型是有符號整數並且長度不超過8個bit，具體的值內容需要通過后續8個bit位的內容來計算
-
0xd1表示當前的值的類型是有符號整數並且長度不超過16個bit，具體的值內容需要通過后續16個bit位的內容來計算
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表示當前的值的類型是字符串並且長度不超過(2^8)-1個bytes ，具體的長度需要通過后續8個bit位的內容來計算，字符串的具體內容是后續長度的byte所表示的內容
-
0xda表示當前的值的類型是字符串並且長度不超過(2^16)-1個bytes ，具體的長度需要通過后續16個bit位的內容來計算，字符串的具體內容是后續長度的byte所表示的內容
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 數組
-
0xdc表示當前的值的類型是數組並且長度不超過(2^16)-1個元素 ，具體的長度需要通過后續16個bit位（兩個byte）的內容來計算，計算出來的值就是數組元素的個數
-
0xdd表示當前的值的類型是數組並且長度不超過(2^32)-1個元素 ，具體的長度需要通過后續32個bit位（4個byte）的內容來計算，計算出來的值就是數組元素的個數
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 小結
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、為什么MessagePack比json序列化使用的字節流更少
3.1 直觀對比
可以通過下圖的兩張圖簡單進行下對比，第一張圖是同一個數據類型的內容用json和messagepack序列化的結果。
從第二張圖可以明顯看到messagepack要比json占用的空間更少。
3.2 序列化結果只有value且value進行了專屬映射
這張圖是MessagePack官網上的，用來進行json和MessagePack序列化結果的對比，實際情況是否確實如此呢？
我本地使用的msgpack-0.6.12版本。
代碼如下：
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 { //初始化一個對象 MyMessage src = new MyMessage(); src.compact = true; src.schema=0; //利用MessagePack進行序列化 MessagePack msgpack = new MessagePack(); // Serialize byte[] bytes = msgpack.write(src); System.out.println("msgpack result length:"+bytes.length); //利用json進行序列化 String jsonResult = JSONObject.toJSON(src).toString(); System.out.println("json result length:"+jsonResult.getBytes().length); } }
運行結果如下：
json result length:27
msgpack result length:3
json序列化的結果是27，和官網圖片中的結果相同。但MessagePack的序列化結果是3，要比官網中的數字小很多。
按照上面圖片的解釋應當是：
-
第一個byte是82，表示序列化后的結果有兩個元素
-
第二個byte是c3，表示第一個元素的值是true
-
第三個byte是00，表示第二個元素的值是0
為了驗證我們的推測，我們可以在MyMessage類中再添加一個boolean類型的屬性，但不給這個屬性賦值，按照java的規范，這個屬性的值就是false，按照MessagePack的規范，就會被轉為一個byte的c2，這樣msgpack序列化后的長度值就是4. 而json序列化的增加值要增加不少，是屬性名稱的長度+5（false的長度）+4（要增加兩個雙引號，一個逗號，一個冒號），如果屬性名稱長度是4，則一共會增加13個byte，總長度就是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 { //初始化一個對象 MyMessage src = new MyMessage(); src.compact = true; src.schema=0; //利用json進行序列化 String jsonResult = JSONObject.toJSON(src).toString(); System.out.println("json result length:"+jsonResult.getBytes().length); //利用MessagePack進行序列化 MessagePack msgpack = new MessagePack(); // Serialize byte[] bytes = msgpack.write(src); System.out.println("msgpack result length:"+bytes.length); } }
上面代碼的執行的結果也符合猜測：
json result length:40
msgpack result length:4
從這個數字上看，MessagePack明顯優於json，特別是在屬性多的情況下差距會更大。即使json中把key去掉，序列化后的結果也要比MessagePack占用的空間大。
3.2 序列化對象的屬性順序不能變動
3.1分析了MessagePack序列化的結果中只包含了value，而不包含key。因而在進行反序列化需要保證類中屬性的順序必須保證完全一致，否則就會出錯：
如果兩個屬性的類型一致，可以反序列化，但是值發生錯亂。
如果兩個屬性的類型不一致，會拋出類型不匹配異常。
3.2.1 順序不同，類型相同
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 { //初始化一個對象 MyMessage src = new MyMessage(); src.compact = true; src.link = false; //利用MessagePack進行序列化 MessagePack msgpack = new MessagePack(); // Serialize byte[] bytes = msgpack.write(src); //利用MessagePack進行反序列化 MyMessage2 dst = msgpack.read(bytes, MyMessage2.class); System.out.println("msgpack 原始數據:" + src); System.out.println("msgpack 反序列化:" + dst); } }
上述代碼的執行結果如下：
msgpack 原始數據:link:false;compact:true msgpack 反序列化:link:true;compact:false
3.2.1 順序不同，類型不同
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 { //初始化一個對象 MyMessage src = new MyMessage(); src.compact = true; src.link = "www.baidu.com"; //利用MessagePack進行序列化 MessagePack msgpack = new MessagePack(); // Serialize byte[] bytes = msgpack.write(src); //利用MessagePack進行反序列化 MyMessage2 dst = msgpack.read(bytes, MyMessage2.class); System.out.println("msgpack 原始數據:" + src); System.out.println("msgpack 反序列化:" + dst); } }
執行結果：
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)