2022年J2SE序列化教程:入门与实践

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"本教程介绍了2022年J2SE中序列化功能在Java编程中的应用。序列化是Java语言中的一种核心特性,用于将对象的状态转换为可存储或传输的形式,以便于跨平台或长期存储后恢复对象的完整状态。在Java中,序列化主要通过`java.io.Serializable`接口和`ObjectOutputStream`与`ObjectInputStream`类来实现。 首先,一个类想要被序列化,必须实现`Serializable`接口。这并不需要提供任何具体的方法实现,而是声明了类支持序列化操作。例如,`Serial`类就是这样一个实现了`Serializable`的示例,包含三个成员变量:`companyId`、`companyAddr`和`companyFlag`。 在`main`方法中,我们创建了一个`Serial`对象`serial1`,并为其赋予初始值。接着,我们通过`FileInputStream`和`FileOutputStream`进行文件操作,创建`ObjectInputStream`和`ObjectOutputStream`实例。利用`ObjectOutputStream`的`writeObject()`方法,我们将`serial1`对象序列化写入文件。然后,关闭流并重新打开文件,用`ObjectInputStream`的`readObject()`方法从文件中读取序列化的数据,并将读取的对象赋值给`Serial`类型的新对象。 序列化和反序列化过程的关键在于它们允许程序在内存之间、网络通信以及持久化存储之间共享和恢复对象状态,这对于构建可扩展的应用和分布式系统至关重要。在实际开发中,序列化还常用于持久化用户会话、保存配置信息、数据库备份等场景。需要注意的是,为了保证跨版本的兼容性和安全性,序列化时需要谨慎处理可能存在的敏感信息,比如密码或私钥等。 本教程通过一个简单的例子展示了Java 2022年中的序列化机制,包括如何声明序列化支持、如何进行对象的序列化与反序列化,以及序列化在实际应用中的应用场景和注意事项。学习和掌握序列化是Java开发者必备的技能之一,有助于提高程序的稳定性和可维护性。"

java.lang.UnsupportedOperationException at java.util.AbstractList.add(AbstractList.java:148) at java.util.AbstractList.add(AbstractList.java:108) at org.apache.commons.collections.CollectionUtils.addAll(CollectionUtils.java:688) at com.bosssoft.hr.train.j2se.util.UtilsDemo.method2(UtilsDemo.java:60) at Test1.testUtilsDemo2(Test1.java:56) 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.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63) at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329) at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293) at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) at org.junit.runners.ParentRunner.run(ParentRunner.java:413) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38) at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:232) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:55)

2023-07-14 上传

java.lang.IllegalArgumentException: Parameter 'directory' is not a directory at org.apache.commons.io.FileUtils.listFiles(FileUtils.java:293) at org.apache.commons.io.FileUtils.listFiles(FileUtils.java:378) at com.bosssoft.hr.train.j2se.util.UtilsDemo.method4(UtilsDemo.java:133) at Test1.testUtilsDemo4(Test1.java:66) 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.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63) at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329) at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293) at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) at org.junit.runners.ParentRunner.run(ParentRunner.java:413) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38) at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:232) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:55)源码如下:public void method4(){ // 获取目录中的所有文件和子目录 Collection<File> files = FileUtils.listFiles(new File("com/bosssoft/hr/train/j2se/util"), new String[]{"*.java"},true); // 遍历文件和子目录 if (files != null) { for (File file : files) { if (file.isDirectory()) { log.info("Directory: " + file.getName()); } else { log.info("File: " + file.getName()); } } } }

2023-07-14 上传

java.lang.ExceptionInInitializerError at com.example.demo.MyBatisExampleDemoTest.test1(MyBatisExampleDemoTest.java:23) 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.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63) at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329) at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293) at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) at org.junit.runners.ParentRunner.run(ParentRunner.java:413) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38) at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:232) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:55) Caused by: org.apache.ibatis.exceptions.PersistenceException: ### Error building SqlSession. ### The error may exist in SQL Mapper Configuration ### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.datasource.DataSourceException: Unknown DataSource property: serverTimezone at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30) at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:52) at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:36) at com.bosssoft.hr.train.j2se.mybatis.utils.MyBatisUtils.<clinit>(MyBatisUtils.java:27) ... 28 more Caused by: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.datasource.DataSourceException: Unknown DataSource property: serverTimezone at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:122) at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:99) at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:50) ... 30 more Caused by: org.apache.ibatis.datasource.DataSourceException: Unknown DataSource property: serverTimezone at org.apache.ibatis.datasource.unpooled.UnpooledDataSourceFactory.setProperties(UnpooledDataSourceFactory.java:55) at org.apache.ibatis.builder.xml.XMLConfigBuilder.dataSourceElement(XMLConfigBuilder.java:329) at org.apache.ibatis.builder.xml.XMLConfigBuilder.environmentsElement(XMLConfigBuilder.java:283) at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:117) ... 32 more

2023-07-15 上传