小编Ian*_*Ian的帖子

有时在处理Java流()时,我发现自己需要使用非终端forEach()来触发副作用,但不会终止处理.

我怀疑我可以使用类似.map(item - > f(item))的方法执行此操作,其中方法f执行副作用并将项目返回到流,但它似乎有点笨拙.

有没有一种标准的处理方式？

我有一个AspectJ跟踪例程设置为使用以下切入点记录方法进入和退出条件:

public aspect Trace {       
    pointcut anyMethodExecuted():       execution (* biz.ianw.lanchecker.*.*(..)) && !within(Trace) && !within( is(AnonymousType) );
    pointcut anyConstructorExecuted():  execution (biz.ianw.lanchecker.*.new(..)) && !within(Trace); 

在我的sendEmail类中,我有一个方法,它调用setDebugOut方法将调试输出重定向到LogOutputStream:

final private static  Logger log = LoggerFactory.getLogger(MailMail.class);
...
LogOutputStream losStdOut = new LogOutputStream() {             
    @Override
    protected void processLine(String line, int level) {
        log.debug(line);
    }
};    

public void sendPlainHtmlMessage(...) {  
    Session session = javaMailSender.getSession();
    PrintStream printStreamLOS = new PrintStream(losStdOut);
    session.setDebugOut(printStreamLOS);
    ...

这很好,除了Trace类切入点截取调用匿名内部类,产生输出:

20:14:18.908 TRACE [biz.ianw.lanchecker.Trace] - Enters method: Logger biz.ianw.lanchecker.MailMail.access$0()
20:14:18.909 TRACE [biz.ianw.lanchecker.Trace] - Exits method: Logger biz.ianw.lanchecker.MailMail.access$0(). …

我正试图在Eclipse下开始使用JMH.我可以从命令行构建一个jar来执行,但是我也希望能够在Eclipse中直接运行它以便于开发.

目前我正在:

java.lang.RuntimeException: ERROR: Unable to find the resource: /META-INF/BenchmarkList

我正在使用来自http://nitschinger.at/Using-JMH-for-Java-Microbenchmarking/的简单入门案例:

public class MyBenchmark {

    @Benchmark
    public void testMethod() {
        // This is a demo/sample template for building your JMH benchmarks. Edit as needed.
        // Put your benchmark code here.
    }

    public static void main(String... args) throws Exception {
          Options opts = new OptionsBuilder()
              .include(".*")
              .warmupIterations(10)
              .measurementIterations(10)
//            .jvmArgs("-server")
              .forks(1)
//            .outputFormat(OutputFormatType.TextReport)
              .build();

          new Runner(opts).run();
        }    
}

我按照JMH文档中的规定生成了POM,并添加了JMH中指定的exec-maven-plugin 无法找到资源:/ META-INF/BenchmarkList:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.sample</groupId> …

我试图从我的 Maven 构建中排除一个资源文件。我复制了 my-jar-with-dependencies.xml 并添加了一个部分。这正确地排除了命名文件被复制到 jar 的 /src/main/resources但文件仍然与其他资源一起被复制到 jar 的顶级目录。

<assembly xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.3" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.3 http://maven.apache.org/xsd/assembly-1.1.3.xsd">
  <!-- TODO: a jarjar format would be better -->
  <id>my-jar-with-dependencies</id>
  <formats>
    <format>jar</format>
  </formats>

  <fileSets>
    <fileSet>
      <directory>${project.basedir}</directory>
      <outputDirectory></outputDirectory>
      <useDefaultExcludes>true</useDefaultExcludes>
      <excludes>
        <exclude>**/lanchecker.properties</exclude>  <!-- this removes it from jar/src/main/resources but *NOT* from jar/ -->
      </excludes>
    </fileSet>
  </fileSets>

  <includeBaseDirectory>false</includeBaseDirectory>
  <dependencySets>
    <dependencySet>
      <outputDirectory>/</outputDirectory>
      <useProjectArtifact>true</useProjectArtifact>
      <unpack>true</unpack>
      <scope>runtime</scope>
    </dependencySet>
  </dependencySets>
</assembly>

我可以阻止 maven-assembly-plugin 执行该复制操作，但仍然可以在开发中访问该文件吗？

更新：

依赖项，根据要求：

  <dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.2.1.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>xml-apis</groupId>
        <artifactId>xml-apis</artifactId>
        <version>1.4.01</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId> …

刚开始在Spring Boot启动时遇到IllegalAccessError.

Exception in thread "main" java.lang.IllegalAccessError: tried to access method org.springframework.core.convert.support.DefaultConversionService.addCollectionConverters(Lorg/springframework/core/convert/converter/ConverterRegistry;)V from class org.springframework.boot.bind.RelaxedConversionService
    at org.springframework.boot.bind.RelaxedConversionService.<init>(RelaxedConversionService.java:52)
    at org.springframework.boot.bind.RelaxedDataBinder.modifyProperties(RelaxedDataBinder.java:148)
    at org.springframework.boot.bind.RelaxedDataBinder.doBind(RelaxedDataBinder.java:128)
    at org.springframework.validation.DataBinder.bind(DataBinder.java:715)
    at org.springframework.boot.bind.PropertiesConfigurationFactory.doBindPropertiesToTarget(PropertiesConfigurationFactory.java:269)
    at org.springframework.boot.bind.PropertiesConfigurationFactory.bindPropertiesToTarget(PropertiesConfigurationFactory.java:241)
    at org.springframework.boot.context.config.ConfigFileApplicationListener.bindToSpringApplication(ConfigFileApplicationListener.java:230)
    at org.springframework.boot.context.config.ConfigFileApplicationListener.postProcessEnvironment(ConfigFileApplicationListener.java:181)
    at org.springframework.boot.context.config.ConfigFileApplicationListener.onApplicationEnvironmentPreparedEvent(ConfigFileApplicationListener.java:166)
    at org.springframework.boot.context.config.ConfigFileApplicationListener.onApplicationEvent(ConfigFileApplicationListener.java:152)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:163)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:136)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:119)
    at org.springframework.boot.context.event.EventPublishingRunListener.publishEvent(EventPublishingRunListener.java:111)
    at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:65)
    at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:54)
    at org.springframework.boot.SpringApplication.doRun(SpringApplication.java:325)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:305)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1124)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1113)
    at biz.ianw.LanCheckerReloader.Application.main(Application.java:23)

这似乎与升级到1.3.0.RELEASE时弹簧启动的问题相似,但我没有覆盖我的Spring版本:

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.3.1.RELEASE</version>
</parent>

<dependencies>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.jsoup</groupId>
        <artifactId>jsoup</artifactId>
        <version>1.8.3</version>
    </dependency> …

我正在尝试编写一个简单的实用程序函数来从Map获取值,如果找不到它来创建一个新的值类并将其放在地图中.

看起来虽然很难在运行时获得地图的关键和值的类,但我能想出的最好的东西是以下几行中可怕的东西.

有没有更好的办法？

private Object getOrCreate( Map<Object, Object> map, Object key, Class<?> mapValueClass ) {
    Object value = map.get( key );      

    if (value == null) {                     
        Constructor<?> con = mapValueClass.getConstructor( key.getClass() );
        value = con.newInstance( key );  
        map.put( key, value );               
    }

    return value;
}

我正在研究一个方面方面,需要知道它从哪里调用.目前我正在使用

new Throwable().getStackTrace();

访问此信息,但每个方面需要几百微秒才能运行.

我看过SecurityManager,但似乎只能得到我的类名.

还有其他我错过的选择吗？

更新

JMH基准测试结果在我对@ apangin答案的评论中提到:

Benchmark                       Mode  Cnt      Score    Error  Units
MyBenchmark.javalangaccess13i   avgt  100   2025.865 ±  8.133  ns/op
MyBenchmark.javalangaccess2i    avgt  100   2648.598 ± 24.369  ns/op  
MyBenchmark.throwable1          avgt  100  12706.978 ± 84.651  ns/op

基准代码:

@Benchmark
public StackTraceElement[] throwable1() {
    return new Throwable().getStackTrace();
}

@SuppressWarnings("restriction")
@Benchmark
public static StackTraceElement javalangaccess2i() {
    Exception e = new Exception();
    return sun.misc.SharedSecrets.getJavaLangAccess().getStackTraceElement(e, 2);
}

@SuppressWarnings("restriction")
@Benchmark
public static StackTraceElement javalangaccess13i() {
    Exception e = new Exception();
    return sun.misc.SharedSecrets.getJavaLangAccess().getStackTraceElement(e, 13);
}

在戴尔XPS13 9343(i5-5200U …