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);}@Overridepublic void start(Future<Void> 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<SQLConnection> sqlConnectionFuture = Future.future();sqlClient.getConnection(sqlConnectionFuture);sqlConnectionFuture.setHandler(connection -> {if (connection.succeeded()) {SQLConnection conn = connection.result();Future<SQLRowStream> streamFuture1 = Future.future();Future<List<User>> streamFuture2 = Future.future();Future<List<JsonArray>> future = Future.future();conn.queryStream("SELECT id, name, t_school_id FROM t_user", streamFuture1);streamFuture1.compose(sqlRowStream -> {List<User> 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<JsonArray> 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();}
}
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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);}
}
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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);}@Overridepublic String toString() {return "User{" +"id='" + id + '\'' +", name='" + name + '\'' +", schoolId='" + schoolId + '\'' +'}';}
// ....
}
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4. pom.xml

    <dependencies><dependency><groupId>io.vertx</groupId><artifactId>vertx-core</artifactId><version>3.4.2</version></dependency><dependency><groupId>io.vertx</groupId><artifactId>vertx-mysql-postgresql-client</artifactId><version>3.4.2</version></dependency><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-api</artifactId><version>1.7.25</version></dependency><dependency><groupId>org.apache.logging.log4j</groupId><artifactId>slf4j-impl</artifactId><version>RELEASE</version></dependency></dependencies>
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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。