MAPPER.XML中怎么把查询条件抽出来

在MapReduce编程模型中，Mapper是负责处理输入数据并生成中间结果的类。在MapReduce框架中，Mapper接收一个键值对（key-value）的数据集合，然后根据特定的条件进行筛选和转换，最后将符合条件的数据输出到Reducer。

在MapReduce程序中，查询条件通常通过Mapper的输入参数或者配置文件中的配置项来指定。以下是如何在MapReduce程序中使用查询条件的步骤：

1. 定义Mapper类：首先，你需要定义一个Mapper类，该类继承自`org.apache.hadoop.mapreduce.Mapper`类。在Mapper类的构造函数中，你需要传入一个`Context`对象，这个对象用于与Reducer进行通信。同时，你还需要设置Mapper的输入参数，这些参数将在Mapper类中进行处理。

```java

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

public class MyMapper extends Mapper {

private final static IntWritable one = new IntWritable(1);

private Text word = new Text();

public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

String[] words = value.toString().split("s+");

for (String word : words) {

if (word.equalsIgnoreCase("query")) {

word.set(one);

} else {

word.set(word);

}

}

context.write(word, one);

}

}

```

2. 配置查询条件：在Mapper类的构造函数中，你可以设置输入参数，这些参数将在Mapper类中进行处理。例如，你可以在Mapper类的构造函数中传入一个字符串数组，该数组包含了所有需要查询的条件。

```java

public MyMapper(Configuration conf) {

super(conf);

this.conf = conf;

this.inputFormatClass = TextInputFormat.class;

this.outputFormatClass = IntWritableOutputFormat.class;

this.numReduceTasks = 1;

this.joinKeyType = LongWritable.class;

this.joinValueType = Text.class;

this.mapOutputKeyType = Text.class;

this.mapOutputValueType = IntWritable.class;

this.mapOutputCompressor = true;

this.mapOutputCompressorCoder = true;

this.mapOutputCompressorOutputKeyType = LongWritable.class;

this.mapOutputCompressorOutputValueType = IntWritable.class;

this.mapOutputCompressorOutputKeyCoder = true;

this.mapOutputCompressorOutputValueCoder = true;

this.mapOutputCompressorOutputKeyCompressor = true;

this.mapOutputCompressorOutputValueCompressor = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this.mapOutputCompressorOutputKeyCompressorCoder = true;

this.mapOutputCompressorOutputValueCompressorCoder = true;

this