环境

Ubuntu 22.04
IntelliJ IDEA 2022.1.3
JDK 17.0.3.1
MyBatis 3.5.10

需求

调整如下Db2 CFG参数：

mon_locktimeout ： HISTORY
mon_deadlock ： WITHOUT_HIST
mon_lockwait ： HISTORY
mon_lw_thresh ： 30000000

要求：若 mon_locktimeout 和 mon_deadlock 本身的设置已经高于 HISTORY 和 WITHOUT_HIST ，则无需修改这两个参数。

对于这几参数的说明，详见Db2的Knowledge Center（例如： https://www.ibm.com/docs/en/db2/11.5?topic=parameters-mon-locktimeout-monitoring-lock-timeout ）。

mon_locktimeout ：默认值是 NONE ，可选值为 NONE ， WITHOUT_HIST ， HISTORY ， HIST_AND_VALUES
mon_deadlock ：默认值是 WITHOUT_HIST ，可选值为 NONE ， WITHOUT_HIST ， HISTORY ， HIST_AND_VALUES
mon_lockwait ：默认值是 NONE ，可选值为 NONE ， WITHOUT_HIST ， HISTORY ， HIST_AND_VALUES
mon_lw_thresh ：默认值是 5000000 ，可选值为 1000 到 MAX_INT （单位是微秒）

要点

获取DB CFG设置

select name, value from table(db_get_cfg()) t1

更新DB CFG设置

call sysproc.admin_cmd((select '
	update db cfg using
	<name> <value>,
	<name> <value>
	......
	' from sysibm.sysdummy1))

可以一次性更新多个参数。

动态生成SQL语句

xxxxxx
<if test="xxx">xxxxxx</if>
xxxxxx

当 test 结果为true时，SQL语句里就会包含对应的 xxxxxx 。

打印SQL语句

为了确认 if 动态生成的SQL语句是否有误，可以在运行SQL之前，打印出SQL语句，方便检查。在 mybatis-config.xml 里添加如下配置：

    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

代码

代码结构如下：

在这里插入图片描述

完整代码如下：

MyMapper.java ：

package dao;

import org.apache.ibatis.annotations.Param;
import pojo.EventMonitorLockingDbCfg;
import java.util.List;

public interface MyMapper {
    public List<EventMonitorLockingDbCfg> doGetDbCfg();

    public void doUpdateDbCfg(@Param("p1")boolean mon_locktimeout_higher, @Param("p2")boolean mon_deadlock_higher);

    default public void updateDbCfg() {
        List<EventMonitorLockingDbCfg> list = doGetDbCfg();

        String MON_LOCKTIMEOUT = "mon_locktimeout";
        String MON_DEADLOCK = "mon_deadlock";

        boolean mon_locktimeout_higher = false;
        boolean mon_deadlock_higher = false;

        for (int i = 0; i < list.size(); i++) {
            EventMonitorLockingDbCfg e = list.get(i);
            String name = e.getName();
            String value = e.getValue();
            if (MON_LOCKTIMEOUT.equals(name)) {
                if ("HIST_AND_VALUES".equals(value)) {
                    mon_locktimeout_higher = true;
                }
            } else if (MON_DEADLOCK.equals(name)) {
                if ("HISTORY".equals(value) || "HIST_AND_VALUES".equals(value)) {
                    mon_deadlock_higher = true;
                }
            }
        }

        doUpdateDbCfg(mon_locktimeout_higher, mon_deadlock_higher);

    }
}

MyMapper.xml ：

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="dao.MyMapper">
    <select id = "doGetDbCfg" resultType="pojo.EventMonitorLockingDbCfg">
        select name, value from table(db_get_cfg()) t1
        where name in ('mon_deadlock', 'mon_locktimeout')
    </select>

    <select id="doUpdateDbCfg" statementType="CALLABLE" timeout="60">
        call sysproc.admin_cmd((select '
            update db cfg using
            <if test="!p1">mon_locktimeout HISTORY</if>
            <if test="!p2">mon_deadlock WITHOUT_HIST</if>
            mon_lockwait HISTORY
            mon_lw_thresh 30000000
            ' from sysibm.sysdummy1))
    </select>
</mapper>

EventMonitorLockingDbCfg.java ：

package pojo;

public class EventMonitorLockingDbCfg {
    private String name;
    private String value;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
}

mybatis-config.xml ：

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <environments default="db2">
        <environment id="db2">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.ibm.db2.jcc.DB2Driver"/>
                <!-- <property name="driver" value="com.mysql.jdbc.Driver"/> -->
                <property name="url" value="jdbc:db2://127.0.0.1:50000/sample"/>
                <property name="username" value="db2inst1"/>
                <property name="password" value="passw0rd"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper class="dao.MyMapper"/>
    </mappers>

</configuration>

TestMybatis.java ：

import dao.MyMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

public class TestMybatis {
    @Test
    public void test1() throws IOException {
        String resource = "mybatis-config.xml";

        InputStream inputStream = Resources.getResourceAsStream(resource);

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        SqlSession sqlSession = sqlSessionFactory.openSession(true);

        try {
            MyMapper mapper = sqlSession.getMapper(MyMapper.class);

            mapper.updateDbCfg();
        } finally {
            sqlSession.close();
        }
    }
}

pom.xml ：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>test0822</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
    </properties>


    <dependencies>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.10</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/com.ibm.db2.jcc/db2jcc -->
        <dependency>
            <groupId>com.ibm.db2.jcc</groupId>
            <artifactId>db2jcc</artifactId>
            <version>db2jcc4</version>
        </dependency>

    </dependencies>

    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>

</project>

运行

场景1

首先查看一下相关的Db2 CFG：

➜  ~ db2 get db cfg | grep -i "MON_LOCKTIMEOUT\|MON_DEADLOCK\|mon_lockwait\|mon_lw_thresh"
 Lock timeout events                   (MON_LOCKTIMEOUT) = NONE
 Deadlock events                          (MON_DEADLOCK) = WITHOUT_HIST
 Lock wait events                         (MON_LOCKWAIT) = NONE
 Lock wait event threshold               (MON_LW_THRESH) = 5000000

运行测试：

/home/ding/Downloads/jdk-17.0.3.1/bin/java -ea -Didea.test.cyclic.buffer.size=1048576 -javaagent:/home/ding/Downloads/idea-IU-221.5921.22/lib/idea_rt.jar=39859:/home/ding/Downloads/idea-IU-221.5921.22/bin -Dfile.encoding=UTF-8 -classpath /home/ding/Downloads/idea-IU-221.5921.22/lib/idea_rt.jar:/home/ding/Downloads/idea-IU-221.5921.22/plugins/junit/lib/junit5-rt.jar:/home/ding/Downloads/idea-IU-221.5921.22/plugins/junit/lib/junit-rt.jar:/home/ding/IdeaProjects/test0822/target/test-classes:/home/ding/IdeaProjects/test0822/target/classes:/home/ding/.m2/repository/junit/junit/4.13.2/junit-4.13.2.jar:/home/ding/.m2/repository/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar:/home/ding/.m2/repository/org/mybatis/mybatis/3.5.10/mybatis-3.5.10.jar:/home/ding/.m2/repository/com/ibm/db2/jcc/db2jcc/db2jcc4/db2jcc-db2jcc4.jar com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 TestMybatis,test1
Logging initialized using 'class org.apache.ibatis.logging.stdout.StdOutImpl' adapter.
PooledDataSource forcefully closed/removed all connections.
PooledDataSource forcefully closed/removed all connections.
PooledDataSource forcefully closed/removed all connections.
PooledDataSource forcefully closed/removed all connections.
Opening JDBC Connection
Created connection 1702143276.
==>  Preparing: select name, value from table(db_get_cfg()) t1 where name in ('mon_deadlock', 'mon_locktimeout')
==> Parameters: 
<==    Columns: NAME, VALUE
<==        Row: mon_locktimeout, NONE
<==        Row: mon_deadlock, WITHOUT_HIST
<==      Total: 2
==>  Preparing: call sysproc.admin_cmd((select ' update db cfg using mon_locktimeout HISTORY mon_deadlock WITHOUT_HIST mon_lockwait HISTORY mon_lw_thresh 30000000 ' from sysibm.sysdummy1))
==> Parameters: 
Closing JDBC Connection [com.ibm.db2.jcc.t4.b@6574a52c]
Returned connection 1702143276 to pool.

Process finished with exit code 0

再次查看DB CFG：

➜  ~ db2 get db cfg | grep -i "MON_LOCKTIMEOUT\|MON_DEADLOCK\|mon_lockwait\|mon_lw_thresh"
 Lock timeout events                   (MON_LOCKTIMEOUT) = HISTORY
 Deadlock events                          (MON_DEADLOCK) = WITHOUT_HIST
 Lock wait events                         (MON_LOCKWAIT) = HISTORY
 Lock wait event threshold               (MON_LW_THRESH) = 30000000

场景2

若原先DB CFG如下：

➜  ~ db2 get db cfg | grep -i "MON_LOCKTIMEOUT\|MON_DEADLOCK\|mon_lockwait\|mon_lw_thresh"
 Lock timeout events                   (MON_LOCKTIMEOUT) = HIST_AND_VALUES
 Deadlock events                          (MON_DEADLOCK) = HISTORY
 Lock wait events                         (MON_LOCKWAIT) = NONE
 Lock wait event threshold               (MON_LW_THRESH) = 5000000

运行测试：

......
==>  Preparing: select name, value from table(db_get_cfg()) t1 where name in ('mon_deadlock', 'mon_locktimeout')
==> Parameters: 
<==    Columns: NAME, VALUE
<==        Row: mon_locktimeout, HIST_AND_VALUES
<==        Row: mon_deadlock, HISTORY
<==      Total: 2
==>  Preparing: call sysproc.admin_cmd((select ' update db cfg using mon_lockwait HISTORY mon_lw_thresh 30000000 ' from sysibm.sysdummy1))
==> Parameters: 
......

再次查看DB CFG：

➜  ~ db2 get db cfg | grep -i "MON_LOCKTIMEOUT\|MON_DEADLOCK\|mon_lockwait\|mon_lw_thresh"
 Lock timeout events                   (MON_LOCKTIMEOUT) = HIST_AND_VALUES
 Deadlock events                          (MON_DEADLOCK) = HISTORY
 Lock wait events                         (MON_LOCKWAIT) = HISTORY
 Lock wait event threshold               (MON_LW_THRESH) = 30000000

可见， MON_LOCKTIMEOUT 和 MON_DEADLOCK 已经足够高，不需修改。

场景3

若原先DB CFG里 MON_LOCKTIMEOUT 和 MON_DEADLOCK 其中之一已经足够高，则运行测试后，只会修改另一个，不再赘述。

intellij-idea mybatis

使用Mybatis调整Db2的cfg

环境

需求

要点

获取DB CFG设置

更新DB CFG设置

动态生成SQL语句

打印SQL语句

代码

运行

场景1

场景2

场景3

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