基于JRebel开发的MySQL Explain插件

mysql--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.47</version> <scope>runtime</scope> </dependency> 执行SQL时，经过跟踪代码执行路径，最终会到达这个方法：com.mysql.jdbc.PreparedStatement#executeInternal

/**
 * Actually execute the prepared statement. This is here so server-side
 * PreparedStatements can re-use most of the code from this class.
 * 
 * @param maxRowsToRetrieve the max number of rows to return
 * @param sendPacket SQL语句packet
 * @param createStreamingResultSet should a ‘streaming‘ result set be created?
 * @param queryIsSelectOnly is this query doing a SELECT?
 */
protected ResultSetInternalMethods executeInternal(int maxRowsToRetrieve, Buffer sendPacket, boolean createStreamingResultSet, boolean queryIsSelectOnly,
        Field[] metadataFromCache, boolean isBatch) throws SQLException {}

其中，参数sendPacket就是最终要执行的完整sql语句。我们需要在这个方法中加入explain sql逻辑。

实现

我们所写的插件应该是通用的，不能侵入现有代码。不限于以下两种实现方式：

• javaagent            -- 相对复杂一点，但是很通用，无特殊依赖
• jrebel自定义插件   -- 需要安装jrebel插件，idea和eclipse均支持

回看标题，本篇仅讲解基于jrebel平台来实现这么一个神奇的插件。关于jrebel自定义插件开发，请参阅官方文档：Custom JRebel plugins   实现过程还是非常轻松的，一起来吧！

1. 新建一个maven项目

pom依赖如下：

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <sdk.version>7.0.0</sdk.version>
</properties>
    
<repositories>
    <repository>
        <id>zt-public</id>
        <url>https://repos.zeroturnaround.com/nexus/content/groups/zt-public</url>
    </repository>
</repositories>

<dependencies>
    <dependency>
        <groupId>org.zeroturnaround</groupId>
        <artifactId>jr-sdk</artifactId>
        <version>${sdk.version}</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>org.zeroturnaround</groupId>
        <artifactId>jr-utils</artifactId>
        <version>${sdk.version}</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.47</version>
        <scope>provided</scope>
    </dependency>
</dependencies>

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2. 编写jrebel CBP

继承org.zeroturnaround.javarebel.integration.support.JavassistClassBytecodeProcessor

package com.example.plugin.mysql.cbp;

public class MySQLExplainCBP extends JavassistClassBytecodeProcessor {

    @Override
    public void process(ClassPool cp, ClassLoader cl, CtClass ctClass) throws Exception {
        LoggerFactory.getInstance().echo("MySQLExplainCBP...");
        // 自定义处理类所在包
        cp.importPackage("com.example.plugin.mysql.explain");

         // 找到方法：com.mysql.jdbc.PreparedStatement#executeInternal
        // 在该方法第一行之前插入自定义逻辑
        CtMethod m = ctClass.getDeclaredMethod("executeInternal");
        m.insertBefore(
                "MySQLExplain.explainSql(this.connection, sendPacket);"
        );
    }
}

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3. 自定义explain逻辑

查看MySQL执行计划

package com.example.plugin.mysql.explain;

public final class MySQLExplain {
    private static final Logger logger = LoggerFactory.getInstance();

    /**
     * 调用者：MySQLExplainCBP#process
     */
    public static void explainSql(com.mysql.jdbc.MySQLConnection conn, com.mysql.jdbc.Buffer sendPacket) {
        byte[] bytes = new byte[sendPacket.getPosition()];
        System.arraycopy(sendPacket.getByteBuffer(), 0, bytes, 0, bytes.length);

        String sql = new String(bytes, 5, bytes.length - 5);
        // 前置检查，检查是否执行计划
        if (!processBefore(sql)) {
            return;
        }

        try {
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery("EXPLAIN " + sql);

            List<ExplainResultVo> explainResultList = new ArrayList<>();
            while (rs.next()) {
                ExplainResultVo explainResultVo = new ExplainResultVo();
                explainResultVo.setId(rs.getString("id"));
                explainResultVo.setSelectType(rs.getString("select_type"));
                explainResultVo.setTable(rs.getString("table"));
                explainResultVo.setPartitions(rs.getString("partitions"));
                explainResultVo.setType(rs.getString("type"));
                explainResultVo.setPossibleKeys(rs.getString("possible_keys"));
                explainResultVo.setKey(rs.getString("key"));
                explainResultVo.setKeyLen(rs.getString("key_len"));
                explainResultVo.setRef(rs.getString("ref"));
                explainResultVo.setRows(rs.getString("rows"));
                explainResultVo.setFiltered(rs.getString("filtered"));
                explainResultVo.setExtra(rs.getString("Extra"));

                explainResultList.add(explainResultVo);
            }

            rs.close();

            // 打印结果
            analyzeResult(sql, explainResultList);
        } catch (Exception se) {
            logger.errorEcho("EXPLAIN SQL异常", se);
        }
    }

    /**
     * 前置检查，检查是否执行计划，自定添加逻辑
     */
    private static boolean processBefore(String sql) {
        return true;
    }

    /**
     * 分析结果，打印执行计划，可自定添加过滤条件
     */
    private static void analyzeResult(String sql, List<ExplainResultVo> explainResultList) {
        ExplainHelper.printExplainResult(sql, explainResultList, showSQL);
    }
}

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4. 编写jrebel插件入口类

实现接口：org.zeroturnaround.javarebel.Plugin，需在pom中配置该类

package com.example.plugin.mysql;

/**
 * 插件注册，需在pom中配置该类
 */
public class MySQLExplainPlugin implements Plugin {
    private static final Logger logger = LoggerFactory.getInstance();

    @Override
    public void preinit() {
        Integration integration = IntegrationFactory.getInstance();
        ClassLoader cl = getClass().getClassLoader();

        logger.echo("MySQL执行计划插件启用, 配置详情: \n" + Config.getMySQLConfTable());
        integration.addIntegrationProcessor(
                cl,
                "com.mysql.jdbc.PreparedStatement",
                new MySQLExplainCBP());
    }

    // 指定依赖条件，依赖存在时才启用本插件
    @Override
    public boolean checkDependencies(ClassLoader cl, ClassResourceSource crs) {
        return crs.getClassResource("com.mysql.jdbc.PreparedStatement") != null;
    }

    @Override
    public String getId() {
        return "mysql-explain-jr-plugin";
    }

    // 省略其余方法，默认返回null即可
}

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5. 在pom中指定插件入口类 

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.6.1</version>
            <configuration>
                <source>8</source>
                <target>8</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <version>3.0.2</version>
            <configuration>
                <archive>
                    <manifestEntries>
                        <JavaRebel-Plugin>com.example.plugin.mysql.MySQLExplainPlugin</JavaRebel-Plugin>
                    </manifestEntries>
                </archive>
            </configuration>
        </plugin>
    </plugins>
</build>

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6. 打包

mvn clean package -Dmaven.test.skip=true

7. 使用该插件

项目需要使用jrebel启动，并且指定该插件所在路径，通过jvm参数指定

-Drebel.plugins=/your/path/mysql-explain-jr-plugin.jar

若生效，控制台会输出“MySQLExplainCBP...”等字样。

8 演示效果

此处加了一些自定义逻辑

• 启动时输出MySQL执行计划配置：

• 执行计划打印示例：

总结

基本实现了功能，可以结合idea插件达到更加便捷友好的使用体验！

项目地址

暂无，稍后补充

参考

Custom JRebel plugins