Hadoop-共同好友（共同关注）案例

￡神魔★判官ぃ 2022-10-19 04:28 197阅读 0赞

## 共同好友案例 ##

以下是博客的好友列表数据,冒号前是一个用户,冒号后是该用户的所有好友(数据中  
的好友关系是单向的)，求出哪些人两两之间有共同好友,及他俩的共同好友都有谁?

数据如下：

A:B,C,D,F,E,O
    B:A,C,E,K
    C:F,A,D,I
    D:A,E,F,L
    E:B,C,D,M,L
    F:A,B,C,D,E,O,M
    G:A,C,D,E,F
    H:A,C,D,E,O
    I:A,O
    J:B,O
    K:A,C,D
    L:D,E,F
    M:E,F,G
    O:A,H,I,J

第一次先找出A、B、…是谁的好友

Mapper

public class SameFriendsFirstMapper extends Mapper<LongWritable, Text, Text, Text> { 
    
        Text k = new Text();
        Text v = new Text();
    
        @Override
        protected void map (LongWritable key, Text value, Context context) throws IOException, InterruptedException { 
    
            // A:B,C,D,F,E,O
            // A的好友有B,C,D,F,E,O
            // 找出X是谁的好友
            // 输出如<B,A>
            String line = value.toString();
            String[] fields = line.split(":");
            v.set(fields[0]);
    
            if (fields.length > 1) { 
                String[] keyFields = fields[1].split(",");
                for (String keyField : keyFields) { 
                    k.set(keyField);
    
                    context.write(k, v);
                }
            }
        }
    }

Reducer

public class SameFriendsFirstReducer extends Reducer<Text, Text, Text, NullWritable> { 
    
        Text k = new Text();
    
        @Override
        protected void reduce (Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException { 
    
            List<String> list = new ArrayList<>();
            for (Text value : values) { 
                list.add(value.toString());
            }
    
            k.set(key.toString() + ":" + String.join(",", list));
    
            context.write(k, NullWritable.get());
        }
    }

第一次运行结果如下：

A:I,K,C,B,G,F,H,O,D
    B:A,F,J,E
    C:A,E,B,H,F,G,K
    D:G,C,K,A,L,F,E,H
    E:G,M,L,H,A,F,B,D
    F:L,M,D,C,G,A
    G:M
    H:O
    I:O,C
    J:O
    K:B
    L:D,E
    M:E,F
    O:A,H,I,J,F

Mapper

public class SameFriendsSecondMapper extends Mapper<LongWritable, Text, Text, Text> { 
    
        Text k = new Text();
        Text v = new Text();
    
        @Override
        protected void map (LongWritable key, Text value, Context context) throws IOException, InterruptedException { 
    
            // A:I,K,C,B,G,F,H,O,D
            // A是I,K,C,B,G,F,H,O,D的好友
            // 输出如<I-K, A>
            String line = value.toString();
            String[] fields = line.split(":");
    
            v.set(fields[0]);
    
            if (fields.length > 1) { 
                String[] keyPreFields = fields[1].split(",");
                for (int i = 0; i < keyPreFields.length - 1; i++) { 
                    String first = keyPreFields[i];
                    for (int j = i + 1; j < keyPreFields.length; j++) { 
                        String second = keyPreFields[j];
    
                        // 防止出现A-D和D-A的情况
                        if (first.compareToIgnoreCase(second) < 0) { 
                            k.set(first + "-" + second);
                        } else { 
                            k.set(second + "-" + first);
                        }
                        context.write(k, v);
                    }
                }
            }
        }
    }

Reducer

public class SameFriendsSecondReducer extends Reducer<Text, Text, Text, Text> { 
    
        Text v = new Text();
    
        @Override
        protected void reduce (Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException { 
    
            List<String> list = new ArrayList<>();
            for (Text value : values) { 
                list.add(value.toString());
            }
    
            v.set(String.join(" ", list));
    
            context.write(key, v);
        }
    }

第二次运行结果：

A-B	C E
    A-C	D F
    A-D	F E
    A-E	B D C
    A-F	C B O D E
    A-G	F D E C
    A-H	D O E C
    A-I	O
    A-J	O B
    A-K	D C
    A-L	E D F
    A-M	F E
    B-C	A
    B-D	E A
    B-E	C
    B-F	E A C
    B-G	C A E
    B-H	E C A
    B-I	A
    B-K	C A
    B-L	E
    B-M	E
    B-O	A
    C-D	F A
    C-E	D
    C-F	D A
    C-G	D F A
    C-H	A D
    C-I	A
    C-K	D A
    C-L	D F
    C-M	F
    C-O	I A
    D-E	L
    D-F	A E
    D-G	E A F
    D-H	E A
    D-I	A
    D-K	A
    D-L	E F
    D-M	E F
    D-O	A
    E-F	B M D C
    E-G	D C
    E-H	D C
    E-J	B
    E-K	D C
    E-L	D
    F-G	C D A E
    F-H	A E O C D
    F-I	O A
    F-J	O B
    F-K	A C D
    F-L	E D
    F-M	E
    F-O	A
    G-H	A D E C
    G-I	A
    G-K	C A D
    G-L	F D E
    G-M	F E
    G-O	A
    H-I	A O
    H-J	O
    H-K	A D C
    H-L	D E
    H-M	E
    H-O	A
    I-J	O
    I-K	A
    I-O	A
    K-L	D
    K-O	A
    L-M	F E