应为BEGIN_OBJECT，但第1行第6列为STRING

Question

我的java代码

public class Recipe {
public static class TokenizerMapper  extends Mapper<Object, Text, Text, IntWritable>{
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
Gson gson = new Gson();
public void map(Object key, Text value, Context context ) throws IOException, InterruptedException {
Roo roo=gson.fromJson(value.toString(), Roo.class);
if (roo.manner_of_death != null) {
word.set(roo.manner_of_death);
} else  {
word.set("none");
}
context.write(word, one);
}
}
public static class IntSumReducer
extends Reducer<Text,IntWritable,Text,IntWritable> {
private IntWritable result = new IntWritable();
public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum);
context.write(key, result);
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length != 2) {
System.err.println("Usage: recipe <in> <out>");
System.exit(2);
}
@SuppressWarnings("deprecation")
Job job = new Job(conf, "Recipe");
job.setJarByClass(Recipe.class);
job.setMapperClass(TokenizerMapper.class);
job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(IntSumReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
// FileInputFormat.addInputPath(job, new Path("hdfs://127.0.0.1:9000/in"));
// FileOutputFormat.setOutputPath(job, new Path("hdfs://127.0.0.1:9000/out"));
System.exit(job.waitForCompletion(true) ? 0 : 1);
// job.submit();
}
}
class Id
{
public String oid;
}
class Roo
{
public Id _id ;
public String resident_status;
public String month_of_death;
public String sex;
public String marital_status; 
public String manner_of_death;
public String autopsy;
public String race;
}

我的JSON

{
"_id" : ObjectId("5bfc49155fa79a44dca1f9b9"),
"resident_status" : "1",
"month_of_death" : "06",
"sex" : "M",
"marital_status" : "M",
"manner_of_death" : "7",
"autopsy" : "N",
"race" : "02"
}
{                                                    
"_id" : ObjectId("5bfc49155fa79a44dca1f56c"),    
"resident_status" : "1",                         
"month_of_death" : "03",                         
"sex" : "F",                                     
"marital_status" : "D",                          
"manner_of_death" : "7",                         
"autopsy" : "N",                                 
"race" : "01"                                    
}                                                    

除id 外，所有字段均为字符串

我的错误

18/11/26 18:02:55 INFO mapreduce。作业：任务Id:attempt_154189350698_0010_m_0000000_0，状态：失败错误：com.google.gson.JsonSyntaxException：java.io.EOFException：第1行第3列输入结束网址：com.google.gson.gson.fromJson(gson.java:813(

26年11月18日18:02:55信息地图缩减。作业：任务Id:attempt_154189350698_0010_m_ 000001_0，状态：失败错误：com.google.gson.JsonSyntaxException：java.lang.IllegalStateException：应为BEGIN_OBJECT，但在第1行为STRING

Answer 1

当你这样做时，

class Id
{
public String oid;
}
class Roo
{
public Id _id ;

你告诉Gson，它正试图解析这种类型的对象

{                                                    
"_id" : {
"oid" : "5bfc49155fa79a44dca1f56c"
}, 
...
}

这不是你所拥有的，而且你也没有有效的JSON，因为ObjectId周围没有引号。

---

第二个问题-MapReduce默认读取单行数据，如果您的输入文件只有两行这样的数据，那也没问题，但JSON仍然应该是有效的

{ "_id" : ... }
{ "_id" : ... }