【20200215】SpringBoot Flink - 《乐谷技术学习笔记（可公开）》

使用spring boot整合flink可以快速的构建起整个应用，将关注点重点放在业务逻辑的实现上。在整合的过程中遇到许多问题，最大的问题是flink流无法访问spring容器中的类，从而导致空指针异常，解决思路是在流中进行spring bean的初始化以获得ApplicationContext，进而使用其getBean方法获取类实例。
软件版本:Spring Boot 2.1.6+Flink1.6.1+JDK1.8
程序主体：

@SpringBootApplication
public class HadesTmsApplication implements CommandLineRunner {
    public static void main(String[] args) {
        SpringApplication application = new SpringApplication(HadesTmsApplication.class);
        application.setBannerMode(Banner.Mode.OFF);
        application.run(args);
    }
    @Override
    public void run(String... args) {
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
FlinkKafkaConsumer010 kafkaConsumer = new FlinkKafkaConsumer010<>("topic-name"), new SimpleStringSchema(), getProperties());
DataStream<String> dataStream = env.addSource(kafkaConsumer);
// 此处省略处理逻辑
dataStream.addSink(new MySink());
    }
private Properties getProperties() {
        Properties properties = new Properties();
        properties.setProperty("bootstrap.servers", bootstrap_servers);
        properties.setProperty("zookeeper.connect", zookeeper_connect);
        properties.setProperty("group.id", group_id);
        properties.setProperty("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        properties.setProperty("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        return properties;
    }
}

说明一下：因为是非web项目，所以实现CommandLineRunner接口，重写run方法。在里面编写流处理逻辑。
如果在MySink中需要使用spring容器中的类，而MySink是一个普通的类，那么是无法访问到的。会引发空指针异常。可能有人想到了ApplicationContextAware这个接口，实现这个接口获取ApplicationContext，也即是：

@Component
public class ApplicationContextUtil implements ApplicationContextAware, Serializable {
    private static final long serialVersionUID = -6454872090519042646L;
    private static ApplicationContext applicationContext = null;
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        if (ApplicationContextUtil.applicationContext == null) {
            ApplicationContextUtil.applicationContext = applicationContext;
        }
    }
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }
    //通过name获取 Bean.
    public static Object getBean(String name) {
        return getApplicationContext().getBean(name);
    }
    //通过class获取Bean.
    public static <T> T getBean(Class<T> clazz) {
        return getApplicationContext().getBean(clazz);
    }
    //通过name,以及Clazz返回指定的Bean
    public static <T> T getBean(String name, Class<T> clazz) {
        return getApplicationContext().getBean(name, clazz);
    }
}

这种做法实际上在flink流处理中也是不可行的，在我之前的flink文章中 Flink读写系列之-读mysql并写入mysql 其中读和写阶段有一个open方法，这个方法专门用于进行初始化的，那么我们可以在这里进行spring bean的初始化。那么MySink改造后即为：

@EnableAutoConfiguration
@MapperScan(basePackages = {"com.xxx.bigdata.xxx.mapper"})
public class SimpleSink extends RichSinkFunction<String> {
    TeacherInfoMapper teacherInfoMapper;
    @Override
    public void open(Configuration parameters) throws Exception {
        super.open(parameters);
        SpringApplication application = new SpringApplication(SimpleSink.class);
        application.setBannerMode(Banner.Mode.OFF);
        ApplicationContext context = application.run(new String[]{});
        teacherInfoMapper = context.getBean(TeacherInfoMapper.class);
    }
    @Override
    public void close() throws Exception {
        super.close();
    }
    @Override
    public void invoke(String value, Context context) throws Exception {
        List<TeacherInfo> teacherInfoList = teacherInfoMapper.selectByPage(0, 100);
        teacherInfoList.stream().forEach(teacherInfo -> System.out.println("teacherinfo:" + teacherInfo.getTeacherId() + "," + teacherInfo.getTimeBit() + "," + teacherInfo.getWeek()));
    }
}

在invoke中就可以访问spring容器中的Mapper方法了。
pom如下：

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.xxx.bigdata</groupId>
    <artifactId>flink-project</artifactId>
    <version>1.0.0</version>
    <name>flink-project</name>
    <packaging>jar</packaging>
    <description>My project for Spring Boot</description>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <flink.version>1.6.1</flink.version>
        <skipTests>true</skipTests>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>ch.qos.logback</groupId>
                    <artifactId>logback-classic</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-java</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-java_2.11</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-connector-kafka-0.10_2.11</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>com.cloudera</groupId>
            <artifactId>ImpalaJDBC41</artifactId>
            <version>2.6.4</version>
        </dependency>
        <dependency>
            <groupId>com.zaxxer</groupId>
            <artifactId>HikariCP</artifactId>
            <version>3.2.0</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.1</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.47</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <sourceDirectory>src/main/java</sourceDirectory>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>true</filtering>
                <includes>
                    <include>application.properties</include>
                    <include>application-${package.environment}.properties</include>
                </includes>
            </resource>
        </resources>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <skip>true</skip>
                    <mainClass>com.miaoke.bigdata.tms.HadesTmsApplication</mainClass>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <!--mybatis plugin to generate mapping file and class-->
            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.5</version>
                <configuration>
                    <configurationFile>${basedir}/src/main/resources/generatorConfig.xml</configurationFile>
                    <overwrite>true</overwrite>
                    <verbose>true</verbose>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>com.cloudera</groupId>
                        <artifactId>ImpalaJDBC41</artifactId>
                        <version>2.6.4</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>
    <profiles>
        <!--开发环境-->
        <profile>
            <id>dev</id>
            <properties>
                <package.environment>dev</package.environment>
            </properties>
            <!--默认环境-->
            <activation>
                <activeByDefault>true</activeByDefault>
            </activation>
        </profile>
        <!--预发布环境-->
        <profile>
            <id>pre</id>
            <properties>
                <package.environment>pre</package.environment>
            </properties>
        </profile>
        <!--生产环境-->
        <profile>
            <id>pro</id>
            <properties>
                <package.environment>pro</package.environment>
            </properties>
        </profile>
    </profiles>
</project>

项目打包使用了默认的spring boot插件，配置了skip为true，如果不配置此项，打包后会多一个BOOT-INF目录，运行时会引起ClassNotFoundException等各种异常，比如KafkaStreming问题，甚至需要反转flink的类加载机制，由child-first变为parent-first(修改flink配置文件)等等。
遇到的问题：
1. java.lang.NoSuchMethodError: com.google.gson.GsonBuilder.setLenient()Lcom/google/gson/GsonBuilder
【20200215】SpringBoot Flink - 图1 GsonBuilder类来自gson-xxx.jar包，而我在自己的项目中执行mvn dependency:tree并没有发现依赖这个包。莫非在flink运行时会使用自己lib库下的gson包，转而去flink的lib库下，发现flink-dist_2.11-1.6.1.jar里包含了gson-xxx包，但是打开这个包一看类中没有setLenient方法，于是在服务器上建立一个commlib，把gson-2.8.0.jar（包含setLenient方法）放进去，然后使用flink run提交时，指定classpath即可。
2.日志冲突
Caused by: java.lang.IllegalArgumentException: LoggerFactory is not a Logback LoggerContext but Logback is on the classpath. Either remove Logback or the competing implementation (class org.slf4j.impl.Log4jLoggerFactory loaded from file:/opt/flink-1.6.1/lib/slf4j-log4j12-1.7.7.jar). If you are using WebLogic you will need to add ‘org.slf4j’ to prefer-application-packages in WEB-INF/weblogic.xml: org.slf4j.impl.Log4jLoggerFactory
排除springboot中的日志即可：

<dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter</artifactId>
       <exclusions>
             <exclusion>
                 <groupId>ch.qos.logback</groupId>
                 <artifactId>logback-classic</artifactId>
             </exclusion>
       </exclusions>
</dependency>

3.flink run提交作业到yarn上时，如果需要指定classpath，则需要指定到确定的jar包，指定目录不可行。那么假如所有依赖包已经放置在目录中，拼接的shell可以这么写：

lib_classpath="";
for jar in `ls /home/hadoop/lib`
do
  jar_suffix=${jar##*.}
  if [ "$jar_suffix" = "jar" ]
  then
    jar_path=" --classpath file:///home/hadoop/lib/$jar "
    lib_classpath=${lib_classpath}${jar_path}
  else
    echo "the jar file $jar it not legal jar file,skip appendig"
  fi
done

拼接后的lib_classpath值如下效果：

--classpath file:///home/hadoop/lib/accessors-smart-1.2.jar  --classpath file:///home/hadoop/lib/akka-actor_2.11-2.4.20.jar

注意：如果jar包放本地文件系统，那么需要每台机器都放一份。