香奈儿网站建设目标,推荐营销型网站建设,搭建电商系统,网站安全和信息化建设文章目录 java中try-with-resources自动关闭io流0 简要说明try-with-resources java中try-with-resources自动关闭io流
0 简要说明
在传统的输入输出流处理中#xff0c;我们一般使用的结构如下所示#xff0c;使用try - catch - finally结构捕获相关异常#xff0c;最后不… 文章目录 java中try-with-resources自动关闭io流0 简要说明try-with-resources java中try-with-resources自动关闭io流
0 简要说明
在传统的输入输出流处理中我们一般使用的结构如下所示使用try - catch - finally结构捕获相关异常最后不管是否有异常我们都将流进行关闭处理 try {//业务代码} catch (SQLException e) {// 异常数据回滚try {connection.rollback();} catch (SQLException ex) {log.error(ERROR_MSG, e);throw new IllegalArgumentException(e);}log.error(ERROR_MSG, e);throw new IllegalArgumentException(e);} finally {if (Objects.nonNull(preparedStatement)) {try {preparedStatement.close();} catch (SQLException e) {log.error(ERROR_MSG, e);throw new IllegalArgumentException(e);}}if (Objects.nonNull(connection)) {try {connection.close();} catch (SQLException e) {log.error(ERROR_MSG, e);throw new IllegalArgumentException(e);}}}try-with-resources
在jdk1.7之后推荐使用try() {} catch(IOException e){}的方式来处理io流它可以自动关闭流。如下所示是一个简单的按行读取文件内容的示例Testpublic void readFileContent() {File file new File(d://DumpStacks.log);try (BufferedReader reader new BufferedReader(new FileReader(file))) {String line;while ((line reader.readLine()) ! null) {log.info(line : 【{}】 , line);}} catch (IOException e) {log.error(error msg : 【{}】, e);throw new RuntimeException(e);}}抛异常情况 java.lang.RuntimeException: java.io.FileNotFoundException: d:\DumpStacks.log (系统找不到指定的文件。) at com.geekmice.springbootselfexercise.NoDaoTest.readFileContent(NoDaoTest.java:347)
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:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)Caused by: java.io.FileNotFoundException: d:\DumpStacks.log (系统找不到指定的文件。) at java.io.FileInputStream.open0(Native Method) at java.io.FileInputStream.open(FileInputStream.java:195) at java.io.FileInputStream.(FileInputStream.java:138) at java.io.FileReader.(FileReader.java:72) at com.geekmice.springbootselfexercise.NoDaoTest.readFileContent(NoDaoTest.java:340)
反编译之后可以看到自动关闭流操作
打开target找到对应字节码文件 Testpublic void readFileContent() {File file new File(d://DumpStascks.log);try {BufferedReader reader new BufferedReader(new FileReader(file));Throwable var3 null;try {String line;try {while((line reader.readLine()) ! null) {log.info(line : 【{}】, line);}} catch (Throwable var13) {var3 var13;throw var13;}} finally {if (reader ! null) {if (var3 ! null) {try {reader.close();} catch (Throwable var12) {var3.addSuppressed(var12);}} else {reader.close();}}}} catch (IOException var15) {log.error(error msg : 【{}】, var15);throw new RuntimeException(var15);}}当使用了try(){}代码块之后代码执行完毕就可以进行流的自动关闭比传统的方式简洁了不少。 try()这部分可以有多个语句语句之间分号隔开也可以同时包含输入流和输出流。最后执行完毕统一关闭。
