轻量级ORM框架---JOOQ

当今企业级开发中，几乎都会用到orm框架，有全自动的orm框架hibernate，也有半自动的orm框架mybatis，还有springboot推荐使用的jpa，作者本人个偏向于mybatis框架（写原生sql真的很爽啊！！！），但是在高并发的场景下，不推荐在sql语句中使用关联查询，更倾向于单张表表冗余查询，在代码中使用stream操作，当然这是题外话。前几天逛论坛意外发现一篇标题为《抛弃mybatis，拥抱jooq》的文章，jooq是什么？随后撸了一遍官网：jooq官网链接

在learn模块中，我们可以看到介绍，入门学习只需要7步骤：

Getting started with the tutorial
Your simplest entry point is probably to get the tutorial running. It shows how to use jOOQ and its code generator with a simple MySQL database
Preparation: Download jOOQ and your SQL driver
Step 1: Create a SQL database and a table
Step 2: Generate classes
Step 3: Write a main class and establish a MySQL connection
Step 4: Write a query using jOOQ's DSL
Step 5: Iterate over results
Step 6: Explore!

好吧，一步步来实现吧！！！

step1：Download jOOQ and your SQL driver

准备所需要的jar包。这里使用的是免费的版本

  org.jooq
  jooq
  3.12.3


  org.jooq
  jooq-meta
  3.12.3


  org.jooq
  jooq-codegen
  3.12.3

jooq模块是jooq的核心jar包。
jooq-meta模块是jooq的元数据包，里面提供了不同类型数据库的元数据。
jooq-codegen模块是自动生成代码所需要的包，可以指定生成的目标代码的包名以及存放位置等信息。

既然要链接数据库，当然少不了sql的driver包

            mysql
            mysql-connector-java
            5.1.26
        

step2：Create a SQL database and a table

创建数据库，以及新建一张表

CREATE DATABASE `library`;

USE `library`;

CREATE TABLE `author` (
  `id` int NOT NULL,
  `first_name` varchar(255) DEFAULT NULL,
  `last_name` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
);

step3：Code generation

在resource文件中，我们创建library.xml文件

    
    
        com.mysql.jdbc.Driver
        jdbc:mysql://localhost:3306/library
        root
        19950617
    

    
        
        org.jooq.codegen.JavaGenerator

        
            
            org.jooq.meta.mysql.MySQLDatabase

            
            library
            .*
            
        

        
            
            test.generated

            
            /Users/fengyue/IdeaProjects/jooq/src/main/java
        
    

注：
com.mysql.jdbc.Driver 是 mysql-connector-java 5中的，
com.mysql.cj.jdbc.Driver 是 mysql-connector-java 6中的
官网使用的是com.mysql.cj.jdbc.Driver，这个根据driver包的版本确定。

官网说将jooq，jooq-meta，jooq-codegen，mysql-connector-java这4个jar包跟library.xml存放与同一目录下。执行命令：

windows：

java -classpath jooq-3.12.3.jar;^
jooq-meta-3.12.3.jar;^
jooq-codegen-3.12.3.jar;^
mysql-connector-java-5.1.18-bin.jar;. ^
org.jooq.codegen.GenerationTool library.xml

Mac/liunx

java -classpath jooq-3.12.3.jar:\
jooq-meta-3.12.3.jar:\
jooq-codegen-3.12.3.jar:\
mysql-connector-java-5.1.18-bin.jar:. \
org.jooq.codegen.GenerationTool library.xml

运行之后会发现，还缺少一个jar。

Exception in thread "main" java.lang.NoClassDefFoundError: org/reactivestreams/Publisher
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        at org.jooq.impl.DSL.using(DSL.java:601)
        at org.jooq.meta.mysql.MySQLDatabase.create0(MySQLDatabase.java:530)
        at org.jooq.meta.AbstractDatabase.create(AbstractDatabase.java:260)
        at org.jooq.meta.AbstractDatabase.create(AbstractDatabase.java:249)
        at org.jooq.meta.AbstractDatabase.setConnection(AbstractDatabase.java:239)
        at org.jooq.codegen.GenerationTool.run0(GenerationTool.java:501)
        at org.jooq.codegen.GenerationTool.run(GenerationTool.java:221)
        at org.jooq.codegen.GenerationTool.generate(GenerationTool.java:216)
        at org.jooq.codegen.GenerationTool.main(GenerationTool.java:188)
Caused by: java.lang.ClassNotFoundException: org.reactivestreams.Publisher
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 21 more

好吧，我也不懂为什么，我也不敢问啊，缺什么补什么吧…

    org.reactivestreams
    reactive-streams
    1.0.2

下载reactive-streams包，放在同级目录中执行命令：
java -classpath reactive-streams-1.0.2.jar:jooq-3.12.3.jar:jooq-meta-3.12.3.jar:jooq-codegen-3.12.3.jar:mysql-connector-java-5.1.26.jar:. org.jooq.codegen.GenerationTool library.xml
会自动生成该目录结构：

好吧，代码生成好了。进入下一步…

Step 4: Connect to your database

// For convenience, always static import your generated tables and jOOQ functions to decrease verbosity:
import static test.generated.Tables.*;
import static org.jooq.impl.DSL.*;

import java.sql.*;

public class Main {
    public static void main(String[] args) {
        String userName = "root";
        String password = "";
        String url = "jdbc:mysql://localhost:3306/library";

        // Connection is the only JDBC resource that we need
        // PreparedStatement and ResultSet are handled by jOOQ, internally
        try (Connection conn = DriverManager.getConnection(url, userName, password)) {
            // ...
        } 

        // For the sake of this tutorial, let's keep exception handling simple
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

这里主要是获取数据库connection。

Step 5: Querying

简单介绍如何使用jooq查询数据，当然还有更多的api等待解锁：

DSLContext create = DSL.using(conn, SQLDialect.MYSQL);
Result result = create.select().from(AUTHOR).fetch();

Step 6: Iterating

for (Record r : result) {
    Integer id = r.getValue(AUTHOR.ID);
    String firstName = r.getValue(AUTHOR.FIRST_NAME);
    String lastName = r.getValue(AUTHOR.LAST_NAME);

    System.out.println("ID: " + id + " first name: " + firstName + " last name: " + lastName);
}

完整代码:

package test;

// For convenience, always static import your generated tables and
// jOOQ functions to decrease verbosity:
import static test.generated.Tables.*;
import static org.jooq.impl.DSL.*;

import java.sql.*;

import org.jooq.*;
import org.jooq.impl.*;

public class Main {

    /**
     * @param args
     */
    public static void main(String[] args) {
        String userName = "root";
        String password = "";
        String url = "jdbc:mysql://localhost:3306/library";

        // Connection is the only JDBC resource that we need
        // PreparedStatement and ResultSet are handled by jOOQ, internally
        try (Connection conn = DriverManager.getConnection(url, userName, password)) {
            DSLContext create = DSL.using(conn, SQLDialect.MYSQL);
            Result result = create.select().from(AUTHOR).fetch();

            for (Record r : result) {
                Integer id = r.getValue(AUTHOR.ID);
                String firstName = r.getValue(AUTHOR.FIRST_NAME);
                String lastName = r.getValue(AUTHOR.LAST_NAME);

                System.out.println("ID: " + id + " first name: " + firstName + " last name: " + lastName);
            }
        } 

        // For the sake of this tutorial, let's keep exception handling simple
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Step 7: Explore!

最后贴了一些参考文档，使用手册的地址：
http://www.jooq.org/learn
http://www.jooq.org/javadoc/latest/
https://groups.google.com/forum/#!forum/jooq-user
http://ikaisays.com/2011/11/01/getting-started-with-jooq-a-tutorial/

下次介绍springboot整合jooq…结束！