Spring Boot GraalVM Native镜像约50MB是否正常？有何优化方案？

我尝试使用GraalVM将一个仅包含主文件的空Spring Boot应用编译为Native镜像，执行gradle nativeCompile后生成的镜像大小约为50MB。查看构建日志（如下所示），请问该大小是否符合预期？是否存在遗漏的优化手段？

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    [1/8] Initializing...                                                                                    (4.9s @ 0.24GB)
     Java version: 17.0.7+8-LTS, vendor version: Oracle GraalVM 17.0.7+8.1
     Graal compiler: optimization level: 2, target machine: x86-64-v3, PGO: ML-inferred
     C compiler: cl.exe (microsoft, x64, 19.36.32534)
     Garbage collector: Serial GC (max heap size: 80% of RAM)
     1 user-specific feature(s)
     - org.springframework.aot.nativex.feature.PreComputeFieldFeature
    Field org.apache.commons.logging.LogAdapter#log4jSpiPresent set to true at build time
    Field org.apache.commons.logging.LogAdapter#log4jSlf4jProviderPresent set to true at build time
    Field org.apache.commons.logging.LogAdapter#slf4jSpiPresent set to true at build time
    Field org.apache.commons.logging.LogAdapter#slf4jApiPresent set to true at build time
    Field org.springframework.cglib.core.AbstractClassGenerator#imageCode set to true at build time
    Field org.springframework.boot.logging.java.JavaLoggingSystem$Factory#PRESENT set to true at build time
    Field org.springframework.core.NativeDetector#imageCode set to true at build time
    Field org.springframework.boot.logging.log4j2.Log4J2LoggingSystem$Factory#PRESENT set to false at build time
    Field org.springframework.boot.logging.logback.LogbackLoggingSystem$Factory#PRESENT set to true at build time
    Field org.springframework.core.KotlinDetector#kotlinPresent set to true at build time
    Field org.springframework.core.KotlinDetector#kotlinReflectPresent set to true at build time
    Field org.springframework.format.support.DefaultFormattingConversionService#jsr354Present set to false at build time
    Field org.springframework.boot.logging.logback.LogbackLoggingSystemProperties#JBOSS_LOGGING_PRESENT set to false at build time
    Field org.springframework.context.event.ApplicationListenerMethodAdapter#reactiveStreamsPresent set to false at build time
    [2/8] Performing analysis...  [*****]                                                                   (12.9s @ 1.21GB)
      11,346 (88.27%) of 12,854 types reachable
      17,177 (67.40%) of 25,485 fields reachable
      58,937 (61.80%) of 95,367 methods reachable
       3,583 types,   134 fields, and 1,826 methods registered for reflection
          78 types,    74 fields, and    62 methods registered for JNI access
           5 native libraries: crypt32, ncrypt, psapi, version, winhttp
    [3/8] Building universe...                                                                               (1.9s @ 1.87GB)
    [4/8] Parsing methods...      [**]                                                                       (4.4s @ 1.35GB)
    [5/8] Inlining methods...     [***]                                                                      (0.5s @ 2.52GB)
    [6/8] Compiling methods...    [*****]                                                                   (28.5s @ 4.55GB)
    [7/8] Layouting methods...    [**]                                                                       (3.2s @ 2.09GB)
    [8/8] Creating image...       [**]                                                                       (3.2s @ 2.62GB)
      32.11MB (59.34%) for code area:    31,614 compilation units
      21.57MB (39.87%) for image heap:  311,575 objects and 33 resources
     440.91kB ( 0.80%) for other data
      54.12MB in total
    ------------------------------------------------------------------------------------------------------------------------
    Top 10 origins of code area:                                Top 10 object types in image heap:
      10.81MB java.base                                            6.62MB byte[] for code metadata
       5.09MB kotlin-reflect-1.8.21.jar                            3.15MB byte[] for java.lang.String
       3.44MB java.xml                                             2.24MB java.lang.String
       3.25MB svm.jar (Native Image)                               2.02MB java.lang.Class
       2.05MB spring-core-6.0.9.jar                                1.88MB byte[] for general heap data
       1.45MB spring-boot-3.1.0.jar                              673.03kB byte[] for reflection metadata
     857.06kB spring-beans-6.0.9.jar                             531.84kB com.oracle.svm.core.hub.DynamicHubCompanion
     754.30kB logback-core-1.4.7.jar                             487.22kB java.util.HashMap$Node
     623.80kB spring-expression-6.0.9.jar                        397.81kB java.util.concurrent.ConcurrentHashMap$Node
     391.42kB kotlin-stdlib-1.8.21.jar                           320.75kB c.o.svm.core.hub.DynamicHub$ReflectionMetadata
       3.23MB for 46 more packages                                 2.94MB for 2231 more object types

是否符合预期 #

这个54MB左右的镜像大小属于正常现象。从日志的资源占比可以看出：

• Java基础库（java.base）占10.81MB，这是Native镜像的基础开销，无法完全移除
• Kotlin相关依赖（kotlin-reflect、kotlin-stdlib）合计占近5.5MB，若为纯Java开发，这部分属于可移除的额外开销
• Spring核心组件（spring-core、spring-boot等）合计约4.3MB，是Spring Boot Native的必要基础依赖
• 日志框架（logback）等组件也占据了部分体积

空Spring Boot Native镜像的常规大小区间在40-60MB，你的结果完全处于合理范围。

可尝试的优化手段 #

• 移除Kotlin相关依赖：如果应用是纯Java开发，检查build.gradle中是否引入了Kotlin插件或kotlin-reflect等依赖，移除后可减少约5MB镜像体积
• 替换轻量日志框架：将logback替换为slf4j-simple，能缩减约700KB的日志组件开销
• 启用激进优化级别：构建时添加参数-PnativeOptimizationLevel=3，对应GraalVM的O3优化级别，可进一步压缩代码体积，但会增加构建时间
• 切换Epsilon GC：若应用为无状态短生命周期服务，可通过--gc=epsilon参数替换默认的Serial GC，减少GC相关代码开销
• 裁剪Java基础库：通过Gradle插件配置--initialize-at-build-time，手动指定无需运行时初始化的类；若应用不使用XML解析，可添加--exclude-config=java.xml移除该模块，减少基础库体积
• 系统级压缩镜像：构建完成后使用upx等工具压缩镜像（注意：该操作可能影响启动速度，需测试验证）

内容的提问来源于stack exchange，提问作者Mehdi