flink 进程中 Java 反射的 java.lang.NoSuchMethodError 异常-6ren

flink 进程中 Java 反射的 java.lang.NoSuchMethodError 异常

转载作者：行者123 更新时间：2023-11-30 06:16:43

我正在尝试使用 google Reflection Library 扩展 flink 流程的业务逻辑。我在运行时遇到了这个异常。有人尝试过同样的问题吗？我怀疑 Maven 冲突，但我不知道。我粘贴了异常和 pom 文件。

pom 文件:

    <?xml version="1.0" encoding="UTF-8"?>
<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>it.almaviva.wtf.mms</groupId>
    <artifactId>mms-integretedmobilitystatusevent-flink-process</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <name>Passing Event Process</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <flink.version>1.4.0</flink.version>
        <!--<slf4j.version>1.7.7</slf4j.version>-->
        <log4j.version>1.2.17</log4j.version>
        <scala.binary.version>2.11</scala.binary.version>
        <junit.version>4.12</junit.version>
        <cassandra.version>3.2.0</cassandra.version>
        <flink.connector.elastic.version>1.4.0</flink.connector.elastic.version>
        <thyco.compiler.version>0.21.0</thyco.compiler.version>
        <jackson.version>2.9.4</jackson.version>
        <cassandra.unit.version>3.3.0.2</cassandra.unit.version>
    </properties>

    <repositories>
        <repository>
            <id>apache.snapshots</id>
            <name>Apache Development Snapshot Repository</name>
            <url>https://repository.apache.org/content/repositories/snapshots/</url>
            <releases>
                <enabled>false</enabled>
            </releases>
            <snapshots>
            </snapshots>
        </repository>
    </repositories>

    <!-- Execute "mvn clean package -Pbuild-jar" to build a jar file out of
              this project! How to use the Flink Quickstart pom: a) Adding new dependencies:
              You can add dependencies to the list below. Please check if the maven-shade-plugin
              below is filtering out your dependency and remove the exclude from there.
              b) Build a jar for running on the cluster: There are two options for creating
              a jar from this project b.1) "mvn clean package" -> this will create a fat
              jar which contains all dependencies necessary for running the jar created
              by this pom in a cluster. The "maven-shade-plugin" excludes everything that
              is provided on a running Flink cluster. b.2) "mvn clean package -Pbuild-jar"
              -> This will also create a fat-jar, but with much nicer dependency exclusion
              handling. This approach is preferred and leads to much cleaner jar files. -->

    <dependencies>
        <!-- Apache Flink dependencies -->
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-core</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-java</artifactId>
            <version>${flink.version}</version>
        </dependency>

        <!-- This dependency is required to actually execute jobs. It is currently pulled in by
flink-streaming-java, but we explicitly depend on it to safeguard against future changes. -->
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-clients_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-java_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-connector-kafka-0.10_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>

        <!-- explicitly add a standard loggin framework, as Flink does not have
                      a hard dependency on one specific framework by default -->

        <!-- https://mvnrepository.com/artifact/ch.qos.logback/logback-classic -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>${log4j.version}</version>
        </dependency>
        <!-- TEST PURPOSE -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>${junit.version}</version>
        </dependency>
        <dependency>
            <groupId>org.cassandraunit</groupId>
            <artifactId>cassandra-unit-shaded</artifactId>
            <version>3.3.0.2</version>
        </dependency>

        <!-- DATASTAX -->

        <dependency>
            <groupId>com.datastax.cassandra</groupId>
            <artifactId>cassandra-driver-extras</artifactId>
            <version>${cassandra.version}</version>
            <exclusions>
                <exclusion>
                    <groupId>io.netty</groupId>
                    <artifactId>*</artifactId>
                </exclusion>
                <exclusion>
                    <artifactId>netty-handler</artifactId>
                    <groupId>io.netty</groupId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>com.datastax.cassandra</groupId>
            <artifactId>cassandra-driver-mapping</artifactId>
            <version>${cassandra.version}</version>
            <exclusions>
                <exclusion>
                    <groupId>io.netty</groupId>
                    <artifactId>*</artifactId>
                </exclusion>
            </exclusions>
        </dependency>


        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-connector-elasticsearch5_2.11</artifactId>
            <version>${flink.connector.elastic.version}</version>
            <scope>compile</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.elasticsearch/elasticsearch-core -->
        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>transport</artifactId>
            <version>5.1.2</version>
        </dependency>

        <dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>5.1.2</version>
        </dependency>

        <dependency>
            <groupId>com.carrotsearch</groupId>
            <artifactId>hppc</artifactId>
            <version>0.7.0</version>
        </dependency>


        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-scala_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-scala_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-cep_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-statebackend-rocksdb_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-connector-cassandra_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.6.1</version>
        </dependency>
        <dependency>
            <groupId>io.flinkspector</groupId>
            <artifactId>flinkspector-datastream_2.11</artifactId>
            <version>0.8.1</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.reflections</groupId>
            <artifactId>reflections</artifactId>
            <version>0.9.11</version>
            <exclusions>
                <exclusion>
                    <artifactId>guava</artifactId>
                    <groupId>com.google.guava</groupId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <profiles>
        <profile>
            <!-- Profile for packaging correct JAR files -->
            <id>build-jar</id>

            <activation>
                <activeByDefault>false</activeByDefault>
            </activation>

            <dependencies>
                <dependency>
                    <groupId>org.apache.flink</groupId>
                    <artifactId>flink-core</artifactId>
                    <version>${flink.version}</version>
                    <scope>provided</scope>
                </dependency>
                <dependency>
                    <groupId>org.apache.flink</groupId>
                    <artifactId>flink-java</artifactId>
                    <version>${flink.version}</version>
                    <scope>provided</scope>
                </dependency>
                <dependency>
                    <groupId>org.apache.flink</groupId>
                    <artifactId>flink-clients_${scala.binary.version}</artifactId>
                    <version>${flink.version}</version>
                    <scope>provided</scope>
                </dependency>
                <dependency>
                    <groupId>org.apache.flink</groupId>
                    <artifactId>flink-streaming-java_${scala.binary.version}</artifactId>
                    <version>${flink.version}</version>
                    <scope>provided</scope>
                </dependency>
                <dependency>
                    <groupId>log4j</groupId>
                    <artifactId>log4j</artifactId>
                    <version>${log4j.version}</version>
                    <scope>provided</scope>
                </dependency>
                <!-- DTO -->
                <dependency>
                    <groupId>com.fasterxml.jackson.core</groupId>
                    <artifactId>jackson-databind</artifactId>
                    <version>${jackson.version}</version>
                </dependency>
                <!-- APACHE CASSANDRA -->
                <dependency>
                    <groupId>com.datastax.cassandra</groupId>
                    <artifactId>cassandra-driver-extras</artifactId>
                    <version>${cassandra.version}</version>
                    <exclusions>
                        <exclusion>
                            <groupId>io.netty</groupId>
                            <artifactId>*</artifactId>
                        </exclusion>
                    </exclusions>
                </dependency>
                <dependency>
                    <groupId>com.datastax.cassandra</groupId>
                    <artifactId>cassandra-driver-mapping</artifactId>
                    <version>${cassandra.version}</version>
                    <exclusions>
                        <exclusion>
                            <groupId>io.netty</groupId>
                            <artifactId>*</artifactId>
                        </exclusion>
                    </exclusions>
                </dependency>
                <dependency>
                    <groupId>org.reflections</groupId>
                    <artifactId>reflections</artifactId>
                    <version>0.9.11</version>
                </dependency>

            </dependencies>

            <build>
                <plugins>
                    <!-- disable the exclusion rules -->
                    <plugin>
                        <groupId>org.apache.maven.plugins</groupId>
                        <artifactId>maven-shade-plugin</artifactId>
                        <version>2.4.1</version>
                        <executions>
                            <execution>
                                <phase>package</phase>
                                <goals>
                                    <goal>shade</goal>
                                </goals>
                                <configuration>
                                    <artifactSet>
                                        <excludes combine.self="override"/>
                                    </artifactSet>
                                </configuration>
                            </execution>
                        </executions>
                    </plugin>
                </plugins>
            </build>
        </profile>
    </profiles>

    <build>
        <plugins>
            <!-- We use the maven-shade plugin to create a fat jar that contains all
          dependencies except flink and it's transitive dependencies. The resulting
          fat-jar can be executed on a cluster. Change the value of Program-Class if
          your program entry point changes. -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.1.0</version>
                <executions>
                    <!-- Run shade goal on package phase -->
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <artifactSet>
                                <excludes>
                                    <!-- This list contains all dependencies of flink-dist Everything
                      else will be packaged into the fat-jar -->
                                    <exclude>org.apache.flink:flink-annotations</exclude>
                                    <exclude>org.apache.flink:flink-shaded-hadoop1_2.10</exclude>
                                    <exclude>org.apache.flink:flink-shaded-hadoop2</exclude>
                                    <exclude>org.apache.flink:flink-shaded-curator-recipes</exclude>
                                    <exclude>org.apache.flink:flink-core</exclude>
                                    <exclude>org.apache.flink:flink-java</exclude>
                                    <!--                                                                    <exclude>org.apache.flink:flink-scala_2.10</exclude> -->
                                    <exclude>org.apache.flink:flink-runtime_2.10</exclude>
                                    <exclude>org.apache.flink:flink-optimizer_2.10</exclude>
                                    <exclude>org.apache.flink:flink-clients_2.10</exclude>
                                    <exclude>org.apache.flink:flink-avro_2.10</exclude>
                                    <exclude>org.apache.flink:flink-examples-batch_2.10</exclude>
                                    <exclude>org.apache.flink:flink-examples-streaming_2.10</exclude>
                                    <exclude>org.apache.flink:flink-streaming-java_2.10</exclude>

                                    <!-- Also exclude very big transitive dependencies of Flink WARNING:
                      You have to remove these excludes if your code relies on other versions of
                      these dependencies. -->
                                    <exclude>org.scala-lang:scala-library</exclude>
                                    <exclude>org.scala-lang:scala-compiler</exclude>
                                    <exclude>org.scala-lang:scala-reflect</exclude>
                                    <exclude>com.typesafe.akka:akka-actor_*</exclude>
                                    <exclude>com.typesafe.akka:akka-remote_*</exclude>
                                    <!--<exclude>io.netty:netty-all</exclude>-->
                                    <exclude>io.netty:netty</exclude>
                                    <exclude>commons-fileupload:commons-fileupload</exclude>
                                    <exclude>org.apache.avro:avro</exclude>
                                    <exclude>commons-collections:commons-collections</exclude>
                                    <exclude>org.codehaus.jackson:jackson-core-asl</exclude>
                                    <exclude>org.codehaus.jackson:jackson-mapper-asl</exclude>
                                    <exclude>com.thoughtworks.paranamer:paranamer</exclude>
                                    <exclude>org.xerial.snappy:snappy-java</exclude>
                                    <exclude>org.apache.commons:commons-compress</exclude>
                                    <exclude>org.tukaani:xz</exclude>
                                    <exclude>com.esotericsoftware.kryo:kryo</exclude>
                                    <exclude>com.esotericsoftware.minlog:minlog</exclude>
                                    <exclude>org.objenesis:objenesis</exclude>
                                    <exclude>com.twitter:chill_*</exclude>
                                    <exclude>com.twitter:chill-java</exclude>
                                    <exclude>commons-lang:commons-lang</exclude>
                                    <exclude>junit:junit</exclude>
                                    <exclude>org.apache.commons:commons-lang3</exclude>
                                    <exclude>log4j:log4j</exclude>
                                    <exclude>org.apache.commons:commons-math</exclude>
                                    <exclude>org.apache.sling:org.apache.sling.commons.json</exclude>
                                    <exclude>commons-logging:commons-logging</exclude>
                                    <exclude>commons-codec:commons-codec</exclude>
                                    <exclude>stax:stax-api</exclude>
                                    <exclude>com.typesafe:config</exclude>
                                    <exclude>org.uncommons.maths:uncommons-maths</exclude>
                                    <exclude>com.github.scopt:scopt_*</exclude>
                                    <exclude>commons-io:commons-io</exclude>
                                    <exclude>commons-cli:commons-cli</exclude>
                                </excludes>
                            </artifactSet>
                            <filters>
                                <filter>
                                    <artifact>org.apache.flink:*</artifact>
                                    <excludes>
                                        <!-- exclude shaded google but include shaded curator -->
                                        <exclude>org/apache/flink/shaded/com/**</exclude>
                                        <exclude>web-docs/**</exclude>
                                    </excludes>
                                </filter>
                                <filter>
                                    <!-- Do not copy the signatures in the META-INF folder. Otherwise,
                      this might cause SecurityExceptions when using the JAR. -->
                                    <artifact>*:*</artifact>
                                    <excludes>
                                        <exclude>META-INF/*.SF</exclude>
                                        <exclude>META-INF/*.DSA</exclude>
                                        <exclude>META-INF/*.RSA</exclude>
                                    </excludes>
                                </filter>
                            </filters>
                            <!-- If you want to use ./bin/flink run <quickstart jar> uncomment
                  the following lines. This will add a Main-Class entry to the manifest file -->
                            <transformers>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>it.almaviva.wtf.mms.integratemobilitystatusevent.PassingEventProcess
                                    </mainClass>
                                </transformer>
                            </transformers>
                            <createDependencyReducedPom>false</createDependencyReducedPom>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <compilerId>jdt</compilerId>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.eclipse.tycho</groupId>
                        <artifactId>tycho-compiler-jdt</artifactId>
                        <version>0.21.0</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>

        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.7.0</version>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                        <compilerId>jdt</compilerId>
                    </configuration>
                    <dependencies>
                        <dependency>
                            <groupId>org.eclipse.tycho</groupId>
                            <artifactId>tycho-compiler-jdt</artifactId>
                            <version>0.21.0</version>
                        </dependency>
                    </dependencies>
                </plugin>

                <plugin>
                    <groupId>org.eclipse.m2e</groupId>
                    <artifactId>lifecycle-mapping</artifactId>
                    <version>1.0.0</version>
                    <configuration>
                        <lifecycleMappingMetadata>
                            <pluginExecutions>
                                <pluginExecution>
                                    <pluginExecutionFilter>
                                        <groupId>org.apache.maven.plugins</groupId>
                                        <artifactId>maven-assembly-plugin</artifactId>
                                        <versionRange>[2.4,)</versionRange>
                                        <goals>
                                            <goal>single</goal>
                                        </goals>
                                    </pluginExecutionFilter>
                                    <action>
                                        <ignore/>
                                    </action>
                                </pluginExecution>
                                <pluginExecution>
                                    <pluginExecutionFilter>
                                        <groupId>org.apache.maven.plugins</groupId>
                                        <artifactId>maven-compiler-plugin</artifactId>
                                        <versionRange>[3.1,)</versionRange>
                                        <goals>
                                            <goal>testCompile</goal>
                                            <goal>compile</goal>
                                        </goals>
                                    </pluginExecutionFilter>
                                    <action>
                                        <ignore/>
                                    </action>
                                </pluginExecution>
                            </pluginExecutions>
                        </lifecycleMappingMetadata>
                    </configuration>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

错误:

22:24:56.552 [main] INFO org.reflections.Reflections - Reflections took 370 ms to scan 1 urls, producing 16 keys and 52 values Exception in thread "main" java.lang.NoSuchMethodError: com.google.common.collect.Sets$SetView.iterator()Lcom/google/common/collect/UnmodifiableIterator; at org.reflections.Reflections.expandSuperTypes(Reflections.java:380) at org.reflections.Reflections.(Reflections.java:126) at org.reflections.Reflections.(Reflections.java:168) at org.reflections.Reflections.(Reflections.java:141) at it.almaviva.wtf.mms.integratemobilitystatusevent.PassingEventProcess.preferredCustomLogicMethod(PassingEventProcess.java:213) at it.almaviva.wtf.mms.integratemobilitystatusevent.PassingEventProcess.main(PassingEventProcess.java:81)

最佳答案

我很确定这不是 Flink 相关的问题。有问题的方法SetsView#iterator由反射调用 0.9.11 来自Guava 20.0 ，您在 pom 中将其排除，而 cassandra-driver-extras 则拉入 Guava 19(即 doesn't have this method )。您可以通过执行来检查:

mvn dependency:tree

您必须以某种方式解决 cassandra 和反射依赖项之间的冲突。您可以尝试将 guava 版本强制为 20.0，删除 cassandra-driver-extras 依赖项或查找没有 guava 依赖项的 cassandra-driver-extras 版本(Flink 正在遮蔽它的 Guava 依赖项，因此 Flink 的用户不必处理此问题)。

关于flink 进程中 Java 反射的 java.lang.NoSuchMethodError 异常，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/49038848/

文章推荐： java - JAX-RS @CookieParam 值从一个请求更改为另一个请求

文章推荐： java - 如何迭代存储为 Object 类型的 Java 集合？

文章推荐： java - 在 Flink 中广播 HashMap

文章推荐： Java: Wicket 口无法找到组件

java - Java 方法如何检索属于该特定方法的方法对象？ ( java )
我正在编写一个具有以下签名的 Java 方法。 void Logger(Method method, Object[] args); 如果一个方法(例如 ABC() )调用此方法 Logger，它应该
java - (Java) Java 找不到我的图像文件
我是 Java 新手。我的问题是我的 Java 程序找不到我试图用作的图像文件一个 JButton。 (目前这段代码什么也没做，因为我只是得到了想要的外观第一的)。这是我的主课代码: packag
java - java Java 有手动垃圾回收吗？
好的，今天我在接受采访，我已经编写 Java 代码多年了。采访中说“Java 垃圾收集是一个棘手的问题，我有几个 friend 一直在努力弄清楚。你在这方面做得怎么样？”。她是想骗我吗？还是我的一生都
java - Java 之谜 - Java
我的 friend 给了我一个谜语让我解开。它是这样的: There are 100 people. Each one of them, in his turn, does the following
java - Java 字节码是否兼容不同版本的 Java？
如果我将使用 Java 5 代码的应用程序编译成字节码，生成的 .class 文件是否能够在 Java 1.4 下运行？如果后者可以工作并且我正在尝试在我的 Java 1.4 应用程序中使用 Jav
java - Java 缺少无符号原始类型是 Java 平台的特征还是 Java 语言的特征？
有关于why Java doesn't support unsigned types的问题以及一些关于处理无符号类型的问题。我做了一些搜索，似乎 Scala 也不支持无符号数据类型。限制是Java和S
java - Java 7 的 Java 字节码可以在其他版本的 Java 中工作吗
我只是想知道在一个 java 版本中生成的字节码是否可以在其他 java 版本上运行最佳答案通常，字节码无需修改即可在较新版本的 Java 上运行。它不会在旧版本上运行，除非您使用特殊参数 (
java -cp 。 test.java 与 java test.java
我有一个关于在命令提示符下执行 java 程序的基本问题。在某些机器上我们需要指定 -cp 。 (类路径)同时执行java程序 (test为java文件名与.class文件存在于同一目录下) jav
java - 使用 Java (Java EE/Java SE) 的数据库应用程序设计模式
我已经阅读 StackOverflow 有一段时间了，现在我才鼓起勇气提出问题。我今年 20 岁，目前在我的家乡(罗马尼亚克卢日-纳波卡)就读 IT 大学。足以介绍:D。基本上，我有一家提供簿记应用
java - Java 中的解析可在 Java 中访问
我有 public JSONObject parseXML(String xml) { JSONObject jsonObject = XML.toJSONObject(xml); r
java - Java 中的解释性语言以及对 Java 方法的调用
我已经在 Java 中实现了带有动态类型的简单解释语言。不幸的是我遇到了以下问题。测试时如下代码: def main() { def ks = Map[[1, 2]].keySet()
java - java 序数 - Java I 类
一直提示输入 1 到 10 的数字 - 结果应将 st、rd、th 和 nd 添加到数字中。编写一个程序，提示用户输入 1 到 10 之间的任意整数，然后以序数形式显示该整数并附加后缀。 public
java - 如何从 Java 执行 Java？
我有这个 DownloadFile.java 并按预期下载该文件: import java.io.*; import java.net.URL; public class DownloadFile {
java - 延迟不适用于 java gui(java)
我想在 GUI 上添加延迟。我放置了 2 个 for 循环，然后重新绘制了一个标签，但这 2 个 for 循环一个接一个地执行，并且标签被重新绘制到最后一个。我能做什么？ for(int i=0;
java - Java 类中的硬编码 Java 列表
我正在对对象 Student 的列表项进行一些测试，但是我更喜欢在 java 类对象中创建硬编码列表，然后从那里提取数据，而不是连接到数据库并在结果集中选择记录。然而，自从我这样做以来已经很长时间了，
java - java 幕后对象创建(java 对象实例化)
我知道对象创建分为三个部分: 声明实例化初始化 classA{} classB extends classA{} classA obj = new classB(1,1); 实例化它必须使用
java - 车辆跟踪系统[java/Java EE]
我有兴趣使用 GPRS 构建车辆跟踪系统。但是，我有一些问题要问以前做过此操作的人: GPRS 是最好的技术吗？人们意识到任何问题吗？我计划使用 Java/Java EE - 有更好的技术吗？如果
java - 逆数组(Java)//逆数组(Java)
我可以通过递归方法反转数组，例如:数组={1,2,3,4,5} 数组结果={5,4,3,2,1}但我的结果是相同的数组，我不知道为什么，请帮助我。 public class Recursion { p
java - Java/Java EE 的构建和集成环境
有这样的标准方式吗？包括 Java源代码-测试代码- Ant 或 Maven联合单元持续集成(可能是巡航控制)ClearCase 版本控制工具部署到应用服务器最后我希望有一个自动构建和集成环境。
java - 我将如何从 java 程序打印文本？ ( java )
我什至不知道这是否可能，我非常怀疑它是否可能，但如果可以，您能告诉我怎么做吗？我只是想知道如何从打印机打印一些文本。有什么想法吗？最佳答案这里有更简单的事情。 import javax.swin

行者123

个人简介

我是一名优秀的程序员,十分优秀！

作者热门文章

滴滴打车优惠券免费领取

全站热门文章

首页

博学

6Ren·AI

商城

flink 进程中 Java 反射的 java.lang.NoSuchMethodError 异常