这期内容当中小编将会给大家带来有关ApacheFlink中Flink数据流编程是怎样的，文章内容丰富且以专业的角度为大家分析和叙述，阅读完这篇文章希望大家可以有所收获。
数据源可以通过StreamExecutionEnvironment.addSource(sourceFunction)方式来创建，Flink也提供了一些内置的数据源方便使用，例如readTextFile(path) readFile()，当然，也可以写一个自定义的数据源（可以通过实现SourceFunction方法，但是无法并行执行。或者实现可以并行实现的接口ParallelSourceFunction或者继承RichParallelSourceFunction）
入门
首先做一个简单入门，建立一个DataStreamSourceApp
Scala
object DataStreamSourceApp {
def main(args: Array[String]): Unit = {
val env = StreamExecutionEnvironment.getExecutionEnvironment
socketFunction(env)
env.execute("DataStreamSourceApp")
}
def socketFunction(env: StreamExecutionEnvironment): Unit = {
val data=env.socketTextStream("192.168.152.45", 9999)
data.print()
}
}这个方法将会从socket中读取数据，因此我们需要在192.168.152.45中开启服务：
nc -lk 9999
然后运行DataStreamSourceApp，在服务器上输入：
iie4bu@swarm-manager:~$ nc -lk 9999
apache
flink
spark
在控制台中也会输出：
3> apache
4> flink
1> spark
前面的 341表示的是并行度。可以通过设置setParallelism来操作：
data.print().setParallelism(1)
Java
public class JavaDataStreamSourceApp {
public static void main(String[] args) throws Exception {
StreamExecutionEnvironment environment = StreamExecutionEnvironment.getExecutionEnvironment();
socketFunction(environment);
environment.execute("JavaDataStreamSourceApp");
}
public static void socketFunction(StreamExecutionEnvironment executionEnvironment){
DataStreamSource<String> data = executionEnvironment.socketTextStream("192.168.152.45", 9999);
data.print().setParallelism(1);
}
}自定义添加数据源方式
Scala
实现SourceFunction接口
这种方式不能并行处理。
新建一个自定义数据源
class CustomNonParallelSourceFunction extends SourceFunction[Long]{
var count=1L
var isRunning = true
override def run(ctx: SourceFunction.SourceContext[Long]): Unit = {
while (isRunning){
ctx.collect(count)
count+=1
Thread.sleep(1000)
}
}
override def cancel(): Unit = {
isRunning = false
}
}这个方法首先定义一个初始值count=1L，然后执行的run方法，方法主要是输出count，并且执行加一操作，当执行cancel方法时结束。调用方法如下：
def main(args: Array[String]): Unit = {
val env = StreamExecutionEnvironment.getExecutionEnvironment
// socketFunction(env)
nonParallelSourceFunction(env)
env.execute("DataStreamSourceApp")
}
def nonParallelSourceFunction(env: StreamExecutionEnvironment): Unit = {
val data=env.addSource(new CustomNonParallelSourceFunction())
data.print()
}输出结果就是控制台一直输出count值。
无法设置并行度，除非设置并行度是1.
val data=env.addSource(new CustomNonParallelSourceFunction()).setParallelism(3)
那么控制台报错：
Exception in thread "main" java.lang.IllegalArgumentException: Source: 1 is not a parallel source
at org.apache.flink.streaming.api.datastream.DataStreamSource.setParallelism(DataStreamSource.java:55)
at com.vincent.course05.DataStreamSourceApp$.nonParallelSourceFunction(DataStreamSourceApp.scala:16)
at com.vincent.course05.DataStreamSourceApp$.main(DataStreamSourceApp.scala:11)
at com.vincent.course05.DataStreamSourceApp.main(DataStreamSourceApp.scala)
继承ParallelSourceFunction方法
import org.apache.flink.streaming.api.functions.source.{ParallelSourceFunction, SourceFunction}
class CustomParallelSourceFunction extends ParallelSourceFunction[Long]{
var isRunning = true
var count = 1L
override def run(ctx: SourceFunction.SourceContext[Long]): Unit = {
while(isRunning){
ctx.collect(count)
count+=1
Thread.sleep(1000)
}
}
override def cancel(): Unit = {
isRunning=false
}
}方法的功能跟上面是一样的。main方法如下：
def main(args: Array[String]): Unit = {
val env = StreamExecutionEnvironment.getExecutionEnvironment
// socketFunction(env)
// nonParallelSourceFunction(env)
parallelSourceFunction(env)
env.execute("DataStreamSourceApp")
}
def parallelSourceFunction(env: StreamExecutionEnvironment): Unit = {
val data=env.addSource(new CustomParallelSourceFunction()).setParallelism(3)
data.print()
}可以设置并行度3，输出结果如下：
2> 1
1> 1
2> 1
2> 2
3> 2
3> 2
3> 3
4> 3
4> 3
继承RichParallelSourceFunction方法
class CustomRichParallelSourceFunction extends RichParallelSourceFunction[Long] {
var isRunning = true
var count = 1L
override def run(ctx: SourceFunction.SourceContext[Long]): Unit = {
while (isRunning) {
ctx.collect(count)
count += 1
Thread.sleep(1000)
}
}
override def cancel(): Unit = {
isRunning = false
}
} def main(args: Array[String]): Unit = {
val env = StreamExecutionEnvironment.getExecutionEnvironment
// socketFunction(env)
// nonParallelSourceFunction(env)
// parallelSourceFunction(env)
richParallelSourceFunction(env)
env.execute("DataStreamSourceApp")
}
def richParallelSourceFunction(env: StreamExecutionEnvironment): Unit = {
val data = env.addSource(new CustomRichParallelSourceFunction()).setParallelism(3)
data.print()
}Java
实现SourceFunction接口
import org.apache.flink.streaming.api.functions.source.SourceFunction;
public class JavaCustomNonParallelSourceFunction implements SourceFunction<Long> {
boolean isRunning = true;
long count = 1;
@Override
public void run(SourceFunction.SourceContext ctx) throws Exception {
while (isRunning) {
ctx.collect(count);
count+=1;
Thread.sleep(1000);
}
}
@Override
public void cancel() {
isRunning=false;
}
} public static void main(String[] args) throws Exception {
StreamExecutionEnvironment environment = StreamExecutionEnvironment.getExecutionEnvironment();
// socketFunction(environment);
nonParallelSourceFunction(environment);
environment.execute("JavaDataStreamSourceApp");
}
public static void nonParallelSourceFunction(StreamExecutionEnvironment executionEnvironment){
DataStreamSource data = executionEnvironment.addSource(new JavaCustomNonParallelSourceFunction());
data.print().setParallelism(1);
}当设置并行度时：
DataStreamSource data = executionEnvironment.addSource(new JavaCustomNonParallelSourceFunction()).setParallelism(2);
那么报错异常：
Exception in thread "main" java.lang.IllegalArgumentException: Source: 1 is not a parallel source
at org.apache.flink.streaming.api.datastream.DataStreamSource.setParallelism(DataStreamSource.java:55)
at com.vincent.course05.JavaDataStreamSourceApp.nonParallelSourceFunction(JavaDataStreamSourceApp.java:16)
at com.vincent.course05.JavaDataStreamSourceApp.main(JavaDataStreamSourceApp.java:10)
实现ParallelSourceFunction接口
import org.apache.flink.streaming.api.functions.source.ParallelSourceFunction;
public class JavaCustomParallelSourceFunction implements ParallelSourceFunction<Long> {
boolean isRunning = true;
long count = 1;
@Override
public void run(SourceContext ctx) throws Exception {
while (isRunning) {
ctx.collect(count);
count+=1;
Thread.sleep(1000);
}
}
@Override
public void cancel() {
isRunning=false;
}
} public static void main(String[] args) throws Exception {
StreamExecutionEnvironment environment = StreamExecutionEnvironment.getExecutionEnvironment();
// socketFunction(environment);
// nonParallelSourceFunction(environment);
parallelSourceFunction(environment);
environment.execute("JavaDataStreamSourceApp");
}
public static void parallelSourceFunction(StreamExecutionEnvironment executionEnvironment){
DataStreamSource data = executionEnvironment.addSource(new JavaCustomParallelSourceFunction()).setParallelism(2);
data.print().setParallelism(1);
}可以设置并行度，输出结果：
1
1
2
2
3
3
4
4
5
5
继承抽象类RichParallelSourceFunction
public class JavaCustomRichParallelSourceFunction extends RichParallelSourceFunction<Long> {
boolean isRunning = true;
long count = 1;
@Override
public void run(SourceContext ctx) throws Exception {
while (isRunning) {
ctx.collect(count);
count+=1;
Thread.sleep(1000);
}
}
@Override
public void cancel() {
isRunning=false;
}
} public static void main(String[] args) throws Exception {
StreamExecutionEnvironment environment = StreamExecutionEnvironment.getExecutionEnvironment();
// socketFunction(environment);
// nonParallelSourceFunction(environment);
// parallelSourceFunction(environment);
richpParallelSourceFunction(environment);
environment.execute("JavaDataStreamSourceApp");
}
public static void richpParallelSourceFunction(StreamExecutionEnvironment executionEnvironment){
DataStreamSource data = executionEnvironment.addSource(new JavaCustomRichParallelSourceFunction()).setParallelism(2);
data.print().setParallelism(1);
}输出结果：
1
1
2
2
3
3
4
4
5
5
6
6
SourceFunction ParallelSourceFunction RichParallelSourceFunction类之间的关系
上述就是小编为大家分享的ApacheFlink中Flink数据流编程是怎样的了，如果刚好有类似的疑惑，不妨参照上述分析进行理解。如果想知道更多相关知识，欢迎关注天达云行业资讯频道。