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

<dependency><groupId>org.jooq</groupId><artifactId>jooq</artifactId><version>3.12.3</version>
</dependency>
<dependency><groupId>org.jooq</groupId><artifactId>jooq-meta</artifactId><version>3.12.3</version>
</dependency>
<dependency><groupId>org.jooq</groupId><artifactId>jooq-codegen</artifactId><version>3.12.3</version>
</dependency>

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

<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.26</version></dependency>

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

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<configuration xmlns="http://www.jooq.org/xsd/jooq-codegen-3.12.0.xsd"><!-- 数据库连接配置 --><jdbc><driver>com.mysql.jdbc.Driver</driver><url>jdbc:mysql://localhost:3306/library</url><user>root</user><password>19950617</password></jdbc><generator><!--jooq是基于java的，这里代表自动生成代码de1ed风格，有-org.jooq.codegen.JavaGenerator-org.jooq.codegen.ScalaGenerator默认是java风格--><name>org.jooq.codegen.JavaGenerator</name><database><!--指定数据库类型，有mysql，h2，postgres，sqlite...但是不支持oracle--><name>org.jooq.meta.mysql.MySQLDatabase</name><!--指定连接的数据库--><inputSchema>library</inputSchema><includes>.*</includes><excludes></excludes></database><target><!--  自动生成代码存放的目标包名--><packageName>test.generated</packageName><!--  自动生成代码存放的路径--><directory>/Users/fengyue/IdeaProjects/jooq/src/main/java</directory></target></generator>
</configuration>

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/Publisherat 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.Publisherat 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…

<dependency><groupId>org.reactivestreams</groupId><artifactId>reactive-streams</artifactId><version>1.0.2</version>
</dependency>

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, internallytry (Connection conn = DriverManager.getConnection(url, userName, password)) {// ...} // For the sake of this tutorial, let's keep exception handling simplecatch (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<Record> 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, internallytry (Connection conn = DriverManager.getConnection(url, userName, password)) {DSLContext create = DSL.using(conn, SQLDialect.MYSQL);Result<Record> 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 simplecatch (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！