需求：socket發(fā)送過來的數(shù)據(jù)，把String類型轉(zhuǎn)成對象，然后把Java對象保存到Mysql數(shù)據(jù)庫中。

創(chuàng)建數(shù)據(jù)庫和表

create database imooc_flink; create table student( id int(11) NOT NULL AUTO_INCREMENT, name varchar(25), age int(10), primary key(id) )

導(dǎo)入mysql依賴：

<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.15</version></dependency>

創(chuàng)建POJO Student

package com.vincent.course05;public class Student {private int id;private String name;private int age;@Overridepublic String toString() {return "Student{" +"id=" + id +", name='" + name + '\'' +", age=" + age +'}';}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;} }

然后創(chuàng)建連接，SinkToMySQL.java

package com.vincent.course05;import org.apache.flink.configuration.Configuration; import org.apache.flink.streaming.api.functions.sink.RichSinkFunction;import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement;public class SinkToMySQL extends RichSinkFunction<Student> {PreparedStatement ps;private Connection connection;/*** open() 方法中建立連接，這樣不用每次 invoke 的時候都要建立連接和釋放連接** @param parameters* @throws Exception*/@Overridepublic void open(Configuration parameters) throws Exception {super.open(parameters);connection = getConnection();String sql = "insert into student(id, name, age) values(?, ?, ?);";ps = this.connection.prepareStatement(sql);}@Overridepublic void close() throws Exception {super.close();//關(guān)閉連接和釋放資源if (connection != null) {connection.close();}if (ps != null) {ps.close();}}/*** 每條數(shù)據(jù)的插入都要調(diào)用一次 invoke() 方法** @param value* @param context* @throws Exception*/@Overridepublic void invoke(Student value, Context context) throws Exception {//組裝數(shù)據(jù)，執(zhí)行插入操作ps.setInt(1, value.getId());ps.setString(2, value.getName());ps.setInt(3, value.getAge());ps.executeUpdate();}private static Connection getConnection() {Connection con = null;try {Class.forName("com.mysql.cj.jdbc.Driver");con = DriverManager.getConnection("jdbc:mysql://192.168.152.45:3306/imooc_flink?useUnicode=true&characterEncoding=UTF-8", "root", "123456");} catch (Exception e) {e.printStackTrace();System.out.println("-----------mysql get connection has exception , msg = " + e.getMessage());}return con;} }

main方法：

public static void main(String[] args) throws Exception {StreamExecutionEnvironment environment = StreamExecutionEnvironment.getExecutionEnvironment();DataStreamSource<String> source = environment.socketTextStream("192.168.152.45", 9999);SingleOutputStreamOperator<Student> studentStream = source.map(new MapFunction<String, Student>() {@Overridepublic Student map(String value) throws Exception {String[] splits = value.split(",");Student student = new Student();student.setId(Integer.parseInt(splits[0]));student.setName(splits[1]);student.setAge(Integer.parseInt(splits[2]));return student;}});studentStream.addSink(new SinkToMySQL());environment.execute("JavaCustomSinkToMysql");}

從socket中獲取數(shù)據(jù)，數(shù)據(jù)格式使用逗號分割，在控制臺中輸入：

nc -lk 9999 1,tom,23

檢查數(shù)據(jù)庫，數(shù)據(jù)庫中多了一條數(shù)據(jù)

mysql> select * from student; +----+------+------+ | id | name | age | +----+------+------+ | 1 | tom | 23 | +----+------+------+ 1 row in set (0.00 sec)

這樣就很方便的使用自定義的sink，寫入到MySQL中去。

總結(jié)：

第一步：繼承RichSinkFunction<T> T就是想要寫入的對象類型

第二步：重寫方法 open/close生命周期方法，invoke每條記錄執(zhí)行一次

默認(rèn)情況下open方法的并行度不是1，跟具體的電腦有關(guān)系。

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