Wener Notes

常见问题

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标签：FAQmusl

Java FAQ

javac 乱码

强制使用 UTF-8

bash
javac -J-Dfile.encoding=UTF-8

环境变量

  • JAVA_TOOL_OPTIONS
    • java, javac, jar 会用
    • 例如 -agentlib:hprof
    • JVMTI 定义
  • _JAVA_OPTIONS
    • 类似 JAVA_TOOL_OPTIONS，但优先级更高
    • 针对 Hotspot
  • JAVA_OPTS
    • 由其他工具使用
    • java 不用
  • JDK_JAVA_OPTIONS
    • jdk9+
    • 类似 JAVA_TOOL_OPTIONS，但只有 java 会用
    • java
  • JAVA_HOME

Property

ini
file.encoding=UTF-8
user.language=en
user.country=US
user.variant=
java.io.tmpdir=
javax.net.ssl.keyStore=
javax.net.ssl.keyStorePassword=
javax.net.ssl.keyStoreType=
javax.net.ssl.trustStore=
javax.net.ssl.trustStorePassword=
javax.net.ssl.trustStoreType=
com.sun.management.jmxremote=

选择 JUL 类逻辑

graph TD

    Start[选择JUL类] --> KVorV[KV or Value only?]
    KVorV --Value--> Duplicate[是否允许重复?]
    Duplicate --Yes--> Sync[是否线程同步?]
    Duplicate--No-->Ordered[是否有序?]
    Ordered--No-->HasSet
    Ordered--Yes-->ByInsertOrValue[插入排序还是值排序?]
    ByInsertOrValue--Insert-->LinkedHashSet
    ByInsertOrValue--Value-->TreeSet
    Sync--Yes-->LIFO[LIFO堆栈操作?]
    LIFO--Yes-->Stack
    LIFO--No-->Vector
    Sync --No--> RandomAccess[随机访问?]
    RandomAccess--Yes-->ArrayList
    RandomAccess --No--> SeqAccess[顺序访问?]
    SeqAccess --Yes--> LinkedList
    SeqAccess --No--> Queue[队列操作?]
    Queue --No--> ArrayList
    Queue --Yes--> FastQueue[快速队列?]
    FastQueue --No--> LinkedList
    FastQueue --Yes--> ArrayDeque

    KVorV--KV-->EntryOrdered[有序?]
    EntryOrdered--Yes-->EntryOrderedBy[顺序基于?]
    EntryOrderedBy--Insert-->LinkedHashMap
    EntryOrderedBy--Key-->KVSync[线程同步?]
    KVSync--Yes-->HashTable
    KVSync--No-->TreeMap
    EntryOrdered--No-->Cache[作为缓存/Value构建成本高?]
    Cache--Yes-->WeakHashMap
    Cache--No-->Equals[equals/==?]
    Equals--equals-->HashMap
    Equals--==-->IdentityHashMap

Why is generic of a return type erased when there is an unchecked conversion of a method parameter in Java 8?

Proxy performance

stackoverflow.com/q/1856242/1870054

deploy

  • -Dspring.profiles.active=development
  • SPRING_PROFILES_ACTIVE

A fatal error has been detected by the Java Runtime Environment

text
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00000000000207f6, pid=1, tid=0x00007f9256df8b38
#
# JRE version: OpenJDK Runtime Environment (8.0_345-b01) (build 1.8.0_345-b01)
# Java VM: OpenJDK 64-Bit Server VM (25.345-b01 mixed mode linux-amd64 compressed oops)
# Derivative: IcedTea 3.24.0
# Distribution: Custom build (Tue Nov  8 21:00:08 UTC 2022)
# Problematic frame:
# C  0x00000000000207f6
  • netty musl
    • -Dio.micrometer.shaded.io.netty.transport.noNative=true
    • -Dio.grpc.netty.shaded.io.netty.transport.noNative=true
    • -Dorg.apache.rocketmq.shaded.io.grpc.netty.shaded.io.netty.transport.noNative=true
    • Netty 4.1.77.Final+ 避免 segfaulting
bash
apk add gcompat
export LD_PRELOAD=/lib/libgcompat.so.0

Unable to get pid of LinuxThreads manager thread

alpine docker 里 java 8 为 pid 1 时出现。

bash
curl -O https://arthas.aliyun.com/arthas-boot.jar
pid=1
touch /proc/${pid}/cwd/.attach_pid${pid} && kill -SIGQUIT ${pid} && sleep 2 && ls /proc/${pid}/root/tmp/.java_pid${pid}
java -jar arthas-boot.jar 1
bash
# musl 无法判断线程模型
getconf GNU_LIBPTHREAD_VERSION

# https://github.com/jattach/jattach
apk add jattach
jattach 1 properties

Java Proxy

  • properties
    • socksProxyHost
    • socksProxyPort=1080
    • socksNonProxyHosts
    • java.net.socks.username
    • java.net.socks.password
    • http.proxyHost
    • http.proxyPort
    • http.nonProxyHosts
      • e.g. localhost|host.mydomain.com
    • ftp.proxHost
    • ftp.proxyPort
    • ftp.nonProxyHosts
  • Datagrip 支持 ?socksProxyHost=&socksProxyPort=
bash
JAVA_FLAGS=-Dhttp.proxyHost=127.0.0.1 -Dhttp.proxyPort=8087
java %JAVA_FLAGS%
java
// proxySet 似乎是无效的
if (needsProxy()) {
    System.getProperties().put("proxySet", "true");
    System.getProperties().put("proxyHost", getProxyHost());
    System.getProperties().put("proxyPort", getProxyPort());
} else {
    System.getProperties().put("proxySet", "false");
    System.getProperties().put("proxyHost", "");
    System.getProperties().put("proxyPort", "");
}

gradle

ini
systemProp.http.proxyHost=127.0.0.1
systemProp.http.proxyPort=8080

Virtual Thread

Spring Boot Tomcat

  • 性能更好
java
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.embedded.tomcat.TomcatProtocolHandlerCustomizer;
import org.springframework.context.annotation.Bean;

import java.util.concurrent.Executors;

@SpringBootApplication
@Slf4j
public class VirtualthreadApplication {

    public static void main(String[] args) {
        SpringApplication.run(VirtualthreadApplication.class, args);
    }

    @Bean
    public TomcatProtocolHandlerCustomizer<?> protocolHandlerVirtualThreadExecutorCustomizer() {
        return protocolHandler -> {
            log.info("Configuring " + protocolHandler + " to use VirtualThreadPerTaskExecutor");
            protocolHandler.setExecutor(Executors.newVirtualThreadPerTaskExecutor());
        };
    }
}

String value length exceeds the maximum allowed (20000000, from StreamReadConstraints.getMaxStringLength())

  • jackson
  • string 字段不能超过 20MB 限制
  • 2.15 之前是 5MB

关联信息

反向链接、本文链接的其他页面和外部资料。

反向链接

  • arthas
    笔记 · Unable to get pid of LinuxThreads manager thread · unable to get pid of linuxthreads manager thread

    alibaba/arthas · IDEA 插件 · https://plugins.jetbrains.com/plugin/13581-arthas-idea · OGNL 语法 · https://arthas.aliyun.com/doc/dashboard.html

References

GitHub8 条
其他外链8 条
最近更新commit 8c45b83Edit

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Java FAQjavac 乱码环境变量Property选择 JUL 类逻辑Why is generic of a return type erased when there is an unchecked conversion of a method parameter in Java 8?Proxy performancedeployA fatal error has been detected by the Java Runtime EnvironmentUnable to get pid of LinuxThreads manager threadJava ProxyVirtual ThreadString value length exceeds the maximum allowed (20000000, from StreamReadConstraints.getMaxStringLength())