flink DataStream Operator算子操作举例

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提示：flink流程序中常用的算子举例

一、DataStream Operator

1. Map

Map 算子的输入流是 DataStream，经过 Map 算子后返回的数据格式是 SingleOutputStreamOperator 类型，获取一个元素并生成一个元素，举个例子：

SingleOutputStreamOperator<Employee> map = employeeStream.map(new MapFunction<Employee, Employee>() {
   
    @Override
    public Employee map(Employee employee) throws Exception {
   
        employee.salary = employee.salary + 5000;
        return employee;
    }
});
map.print();

每个Employee对象的salary 值加5000后出来

2.FlatMap

FlatMap 算子的输入流是 DataStream，经过 FlatMap 算子后返回的数据格式是 SingleOutputStreamOperator 类型，获取一个元素并生成零个、一个或多个元素，举个例子：

SingleOutputStreamOperator<Employee> flatMap = employeeStream.flatMap(new FlatMapFunction<Employee, Employee>() {
   
    @Override
    public void flatMap(Employee employee, Collector<Employee> out) throws Exception {
   
        if (employee.salary >= 40000) {
   
            out.collect(employee);
        }
    }
});
flatMap.print();

每个Employee对象的salary 值大于40000的出来

3.Filter

对每个元素都进行判断，返回为 true 的元素，如果为 false 则丢弃数据，上面的代码也可以用filter来做：

SingleOutputStreamOperator<Employee> filter = employeeStream.filter(new FilterFunction<Employee>() {
   
    @Override
    public boolean filter(Employee employee) throws Exception {
   
        if (employee.salary >= 40000) {
   
            return true;
        }
        return false;
    }
});
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