{"id":25939354,"url":"https://github.com/hellyguo/inmemclassloaddemo","last_synced_at":"2025-10-25T15:36:11.368Z","repository":{"id":262183471,"uuid":"886461474","full_name":"hellyguo/InMemClassLoadDemo","owner":"hellyguo","description":"demo for loading classes in memory","archived":false,"fork":false,"pushed_at":"2024-12-07T06:13:35.000Z","size":61,"stargazers_count":0,"open_issues_count":0,"forks_count":0,"subscribers_count":0,"default_branch":"main","last_synced_at":"2024-12-07T07:18:58.105Z","etag":null,"topics":["classloading","demo","jdk11","jdk17","jdk8"],"latest_commit_sha":null,"homepage":"","language":"Java","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"mit","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/hellyguo.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":"LICENSE","code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null}},"created_at":"2024-11-11T02:35:26.000Z","updated_at":"2024-12-07T06:13:33.000Z","dependencies_parsed_at":null,"dependency_job_id":"d5df0e0f-1e9f-4a15-9e55-299ff93ccc2a","html_url":"https://github.com/hellyguo/InMemClassLoadDemo","commit_stats":null,"previous_names":["hellyguo/inmemclassloaddemo"],"tags_count":0,"template":false,"template_full_name":null,"repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/hellyguo%2FInMemClassLoadDemo","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/hellyguo%2FInMemClassLoadDemo/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/hellyguo%2FInMemClassLoadDemo/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/hellyguo%2FInMemClassLoadDemo/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/hellyguo","download_url":"https://codeload.github.com/hellyguo/InMemClassLoadDemo/tar.gz/refs/heads/main","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":241780477,"owners_count":20019061,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["classloading","demo","jdk11","jdk17","jdk8"],"created_at":"2025-03-04T04:16:47.468Z","updated_at":"2025-10-25T15:36:06.334Z","avatar_url":"https://github.com/hellyguo.png","language":"Java","funding_links":[],"categories":[],"sub_categories":[],"readme":"# Demo: Loading classes in memory\n\n[中文版](README_cn.md)\n\n## jdk8\n\n### use `ClassLoader#defineClass`\n\n1. define a class loader, extends `URLClassLoader`\n2. define a new public method, call `defineClass` indirectly\n\n```java\n    public Class\u003c?\u003e loadClassFromBytes(String className, byte[] bytes) {\n        return this.defineClass(className, bytes, 0, bytes.length);\n    }\n```\n\n### use `Unsafe#defineAnonymousClass`\n\n\u003e need to use `sun.misc.Unsafe`, which is not recommended\n\n```java\n    public Class\u003c?\u003e loadClass(String className, byte[] classBytes) {\n        return UNSAFE.defineAnonymousClass(SimTarget.class, classBytes, EMPTY_OBJECTS);\n    }\n```\n\n## jdk11\n\n### use `ClassLoader#defineClass`\n\nsame as `jdk8`\n\n### use `Unsafe#defineAnonymousClass`\n\n\u003e need to use jvm argument: `--add-exports java.base/jdk.internal.misc=\u003cmodule\u003e`\n\n```java\n    public Class\u003c?\u003e loadClass(String className, byte[] classBytes) {\n        return UNSAFE.defineAnonymousClass(AnonClassHolder.class, classBytes, EMPTY_OBJECTS);\n    }\n```\n\n## jdk17\n\n### use `ClassLoader#defineClass`\n\nsame as `jdk8`\n\n### use `MethodLookup#defineHiddenClass`\n\n\u003e need to let the hidden class and the holder class in the same package!\n\n```java\n    public static Class\u003c?\u003e loadClass(String className, byte[] classBytes) {\n        if (!className.startsWith(PACKAGE_NAME)) {\n            throw new RuntimeException(\"not same package, should failed\");\n        }\n        try {\n            MethodHandles.Lookup lookup = MethodHandles.lookup();\n            return lookup.defineHiddenClass(classBytes, true,\n                                            MethodHandles.Lookup.ClassOption.NESTMATE,\n                                            MethodHandles.Lookup.ClassOption.STRONG)\n                         .lookupClass();\n        } catch (IllegalAccessException e) {\n            throw new RuntimeException(e);\n        }\n    }\n```\n\n## HowTo\n\n1. (`optional`) cd `demo-inmem-base`\n2. (`optional`) compile\n    \n    ```shell\n    mvn package -Dmaven.test.skip=true\n    # or\n    mvnd package -Dmaven.test.skip=true\n    ```\n    \n3. (`optional`) call `class2bytes.sh`, generate the Java file, which is hold bytes.\n4. test in `demo-inmem-jdk8`/`demo-inmem-jdk11`/`demo-inmem-jdk17`\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fhellyguo%2Finmemclassloaddemo","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fhellyguo%2Finmemclassloaddemo","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fhellyguo%2Finmemclassloaddemo/lists"}