Vert.x MySQLClient体验-白红宇

文章背景

消除回调地狱

先查询学生(包含学校的Id)，然后使用学校的ID，去学校表查询学校的详细信息

1. DbVerticle.java

import com.xiaoniu.db.entity.User;import com.xiaoniu.db.utils.Utils;import io.vertx.core.AbstractVerticle;import io.vertx.core.Future;import io.vertx.core.json.JsonArray;import io.vertx.core.json.JsonObject;import io.vertx.ext.asyncsql.MySQLClient;import io.vertx.ext.sql.SQLClient;import io.vertx.ext.sql.SQLConnection;import io.vertx.ext.sql.SQLRowStream;import java.util.ArrayList;import java.util.List;/** * Created by sweet on 2017/9/13. */public class DbVerticle extends AbstractVerticle {  private String sql = "SELECT id, name FROM t_school WHERE id IN (";  private SQLClient sqlClient;  public static void main(String[] args) {    Runner.runExample(DbVerticle.class);  }  @Override  public void start(Future
    
      startFuture) throws Exception {    JsonObject c = new JsonObject();    c.put("username", "root").put("password", "main")      .put("host","127.0.0.1").put("database", "sqldemo2");    sqlClient = MySQLClient.createShared(vertx, c);    Future
     
       sqlConnectionFuture = Future.future();    sqlClient.getConnection(sqlConnectionFuture);    sqlConnectionFuture.setHandler(connection -> {      if (connection.succeeded()) {        SQLConnection conn = connection.result();        Future
      
        streamFuture1 = Future.future();        Future
       
        
         > streamFuture2 = Future.future();        Future
         
          
           > future = Future.future(); conn.queryStream("SELECT id, name, t_school_id FROM t_user", streamFuture1); streamFuture1.compose(sqlRowStream -> { List
           
             users = new ArrayList<>(); sqlRowStream.handler(jsonArray -> { System.out.println(jsonArray); users.add(new User(jsonArray)); }); System.out.println("user size: " + users.size()); streamFuture2.complete(users); }, streamFuture2).compose(users -> { List
            
              list = new ArrayList<>(); JsonArray collect = users.parallelStream() .map(User::getSchoolId) .collect(JsonArray::new, JsonArray::add, JsonArray::addAll); String sql2 = sql += Utils.placeholder("?", collect.size(), ", ") + ")"; conn.queryStreamWithParams(sql2, collect, schoolResult -> { if (schoolResult.failed()){ schoolResult.cause().printStackTrace(); return; } schoolResult.result().handler(jsonArray1 -> { if (jsonArray1 != null && jsonArray1.size() > 0) list.add(jsonArray1); }); future.complete(list); }); }, future); future.setHandler(list -> { conn.close(); // 关闭流 if (list.failed()) { list.cause().printStackTrace(); return; } System.out.println("-----"); list.result().forEach(System.out::println); }); } else { connection.cause().printStackTrace(); System.err.println(connection.cause().getMessage()); } }); startFuture.complete(); }}复制代码

2. Utils.java

public class Utils {  public static void main(String[] args) {    System.out.println(placeholder("?", 5, ","));  }    private Utils(){}  /**   * 生成占位符   * (?, 5, ",")   * ?,?,?,?,?   * @param symbol ？   * @param count  出现个数   * @param delimiter 分割符   * @return   */  public static String placeholder(String symbol, Integer count, String delimiter) {    String[] s = new String[count];    for (int i = 0; i < count; i++) {      s[i] = symbol;    }    return String.join(delimiter, s);  }}复制代码

3. User.java

public class User {  private String id;  private String name;  private String schoolId;  public User() {  }  public User(String id, String name) {    this.id = id;    this.name = name;  }  public User(JsonArray jsonArray) {    this.id = jsonArray.getString(0);    this.name = jsonArray.getString(1);    this.schoolId = jsonArray.getString(2);  }  @Override  public String toString() {    return "User{" +            "id='" + id + '\'' +            ", name='" + name + '\'' +            ", schoolId='" + schoolId + '\'' +            '}';  }// ....}复制代码

4. pom.xml


            
                 
      
       io.vertx
                  
      
       vertx-core
                  
      
       3.4.2
              
             
                 
      
       io.vertx
                  
      
       vertx-mysql-postgresql-client
                  
      
       3.4.2
              
             
                 
      
       org.slf4j
                  
      
       slf4j-api
                  
      
       1.7.25
              
             
                 
      
       org.apache.logging.log4j
                  
      
       slf4j-impl
                  
      
       RELEASE
              
         
    复制代码

5. Runner.java

这个文件是官方提供的方便在 IDE中运行的类，https://github.com/vert-x3/vertx-examples/blob/master/core-examples/src/main/java/io/vertx/example/util/Runner.java。