怎么创建运行上述程序的Hadoop Job程序,具体完整的且能够跑通的代码是什么?
时间: 2024-09-19 20:09:29 浏览: 39
Hadoop提交Job执行MR程序代码.zip
创建并运行Hadoop MapReduce程序涉及几个关键步骤,这里以Java编写为例,因为Hadoop通常用Java作为主要开发语言:
1. **创建`JobConf`对象**: 这是Hadoop Job的基本配置,包含了map/reduce任务的相关信息。
```java
Configuration conf = new Configuration();
Job job = Job.getInstance(conf, "exampleJob");
```
2. **定义Mapper和Reducer**: 创建`Mapper`和`Reducer`类,它们是Hadoop MapReduce的核心逻辑。假设我们有一个简单的mapper和reducer:
```java
// Mapper.java
public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
// ... 实现你的map逻辑 ...
}
// Reducer.java
public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
// ... 实现你的reduce逻辑 ...
}
```
3. **设置Mapper和Reducer**: 将你的Mapper和Reducer类添加到job配置中:
```java
job.setMapperClass(Mapper.class);
job.setReducerClass(Reducer.class);
```
4. **设置输入和输出路径**: 指定你的数据源和结果保存位置。
```java
FileInputFormat.addInputPath(job, new Path("inputDirectory"));
FileOutputFormat.setOutputPath(job, new Path("outputDirectory"));
```
5. **提交作业**:
```java
boolean success = job.waitForCompletion(true);
if (success) {
System.out.println("Job completed successfully!");
} else {
System.err.println("Job failed.");
}
```
完整代码示例可能看起来像这样(简化版):
```java
// 前面部分已经列出
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
Job job = Job.getInstance(conf, "exampleJob");
// ... Mapper and Reducer classes ...
job.setJarByClass(MyJobDriver.class); // 如果有自定义JAR包
job.setMapperClass(Mapper.class);
job.setReducerClass(Reducer.class);
// ... set input/output paths ...
boolean result = job.waitForCompletion(true);
if (result) {
System.out.println("Job succeeded.");
} else {
System.exit(-1);
}
}
```
请注意,这只是一个基本框架,实际应用中可能还需要处理文件分片(split)、序列化/反序列化以及错误处理等细节。
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