Join关联联系案例

一、封装类：

public class Bean implements Writable {
    private String orderId;
    private String userId;
    private String name;
    private String age;
    private String userName;
    private String firstName;

    public Bean() {
    }

    public Bean(String orderId, String userId, String name, String age, String userName, String firstName) {
        this.orderId = orderId;
        this.userId = userId;
        this.name = name;
        this.age = age;
        this.userName = userName;
        this.firstName = firstName;
    }

    public String getOrderId() {
        return orderId;
    }

    public void setOrderId(String orderId) {
        this.orderId = orderId;
    }

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    @Override
    public String toString() {
        return "orderId='" + orderId + '\'' +
                ", userId='" + userId + '\'' +
                ", name='" + name + '\'' +
                ", age='" + age + '\'' +
                ", userName='" + userName + '\'' +
                ", firstName='" + firstName + '\'' ;
    }

    @Override
    public void write(DataOutput dataOutput) throws IOException {
        dataOutput.writeUTF(this.orderId);
        dataOutput.writeUTF(this.userId);
        dataOutput.writeUTF(this.name);
        dataOutput.writeUTF(this.age);
        dataOutput.writeUTF(this.userName);
        dataOutput.writeUTF(this.firstName);
    }

    @Override
    public void readFields(DataInput dataInput) throws IOException {
        this.orderId = dataInput.readUTF();
        this.userId = dataInput.readUTF();
        this.name = dataInput.readUTF();
        this.age = dataInput.readUTF();
        this.userName = dataInput.readUTF();
        this.firstName = dataInput.readUTF();
    }
}

二、Mapper类：

public class GoodsMapper extends Mapper<LongWritable,Text,Text,JoinBean> {

    private String fileName;
    JoinBean joinBean = new JoinBean();
    @Override
    protected void setup(Context context) throws IOException, InterruptedException {
         FileSplit split = (FileSplit) context.getInputSplit();
         fileName = split.getPath().getName();
    }

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

        String[] lien = value.toString().split(",");
        if (fileName.startsWith("order")){
            joinBean.setOrderId(lien[0]);
            joinBean.setUserId(lien[1]);
            joinBean.setAge("NULL");
            joinBean.setName("NULL");
            joinBean.setUserName("NULL");
            joinBean.setFistName("order");
        }
        if (fileName.startsWith("user")){
            joinBean.setOrderId("NULL");
            joinBean.setUserId(lien[0]);
            joinBean.setAge(lien[2]);
            joinBean.setName(lien[1]);
            joinBean.setUserName(lien[3]);
            joinBean.setFistName("user");
        }
        
        //以用户名为key ，把数据进行分文件组合成javabean，然后放入context中，shuffle会自动分区，排序map阶段的数据。
        context.write(new Text(joinBean.getUserId()),joinBean);
    }
}

三、Reducer类：

1.注意for循环迭代器Values的括号（引发错误：重复K，null）！

2.注意将BeanUtils.写在if比较语句的里面！简便了bean.setOrderId(value.getOrderId());

3.注意遍历链表里的Bean时，context输出的K，V要写在for括号的里面！

4.注意复制文件BeanUtils.copyProperties(joinBean1,value);

public class GoodsReducer extends Reducer<Text,JoinBean,JoinBean,NullWritable> {

    @Override
    protected void reduce(Text key, Iterable<JoinBean> values, Context context) throws IOException, InterruptedException {

        //user类集合
        List<JoinBean> joinBeans = new ArrayList<>();
        //保存orderid的对象
        JoinBean joinBean = new JoinBean();
        //区分对象是order还是user
        for (JoinBean value : values) {
            if (value.getFistName().equals("order")){
                joinBean.setOrderId(value.getOrderId());
                joinBean.setUserId(value.getUserId());
            }
            if (value.getFistName().equals("user")){
                JoinBean joinBean1 = new JoinBean();
                try {
                    BeanUtils.copyProperties(joinBean1,value);
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                } catch (InvocationTargetException e) {
                    e.printStackTrace();
                }
                joinBeans.add(joinBean1);
            }
        }

        for (JoinBean bean : joinBeans) {
            bean.setOrderId(joinBean.getOrderId());
            context.write(bean,NullWritable.get());
        }
    }
}

四、测试类：

1.创建Configuration环境

2.创建Job添加conf环境

3.设置整个job所用的那些类在哪个Jar包

4.设置job使用的mapper和reducer的类

5.设置mapper的输出数据KV类型

6.指定reducer的输出数据KV类型

7.指定要处理的输入数据存放路径

8.指定要处理的输出数据存放路径

9.将job提交给集群运行