開發小知識-mybatis-plus自動填充與讀寫分離

時間 2020-10-27

標籤 java mysql spring sql 數據庫 apache 網絡 session mybatis app 欄目 MyBatis 简体版

原文原文鏈接

mybatis-plus 自動填充

說明

咱們在設計表結構的時候,每每會額外添多以下幾個字段java

create_time【表字段】-- createTime【實體字段】：建立時間mysql

update_time【表字段】-- updateTime【實體字段】：更新時間spring

create_by【表字段】-- createBy 【實體字段】: 建立人sql

update_by【表字段】--updateBy 【實體字段】：更新人數據庫

del_flag【表字段】-- delFlag【實體字段】 : 邏輯刪除標識【0:未刪除、1:已刪除】apache

在編寫實體類【與數據映射】的時候，不能總在每一個類上都編寫上述幾個屬性，顯得有些冗餘，因而咱們將這幾個屬性提取出來網絡

並在對應的屬性上標註mybatis-plus的填充註解，那麼全部繼承BaseEntity的類將會擁有createTime,updateTime屬性，繼承DefaultEntity的類將會擁有createTime、updateTime、createBy、updateBy、delFlag屬性。session

至於爲何會設計兩個類，是由於有些中間表可能不須要用到createBy、updateBy、delFlag屬性，只須要createTime,updateTime屬性。mybatis

依賴引入

<dependencies>
        <!--mybatis-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.2</version>
        </dependency>
             <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
        </dependency>
    </dependencies>

公用實體類定義

package com.cloud.pango.common.core.entity;

import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.annotation.TableField;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.ToString;

import java.util.Date;

@Data
@ToString
@EqualsAndHashCode
public class BaseEntity{

    @TableField(fill = FieldFill.INSERT)//插入時填充
    private Date createTime;

    @TableField(fill = FieldFill.INSERT_UPDATE)//插入貨更新時填充
    private Date updateTime;
}

package com.cloud.pango.common.core.entity;

import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableLogic;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.ToString;

@Data
@ToString
@EqualsAndHashCode
public class DefaultEntity extends BaseEntity{

    @TableField(fill = FieldFill.INSERT) //插入時填充
    private String createBy;

    @TableField(fill = FieldFill.INSERT_UPDATE)//插入或更新時填充
    private String updateBy;

    @TableField(fill = FieldFill.INSERT) //插入時填充
    @TableLogic//邏輯刪除
    private Integer delFlag;
}

自動填充處理

package com.cloud.pango.common.mybatis;
import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.beans.factory.annotation.Autowired;
import java.util.Date;

@Slf4j
public class EntityMetaObjectHanlder implements MetaObjectHandler {

    private final static String CREATE_TIME = "createTime";

    private final static String UPDATE_TIME = "updateTime";

    private final static String CREATE_BY = "createBy";

    private final static String UPDATE_BY = "updateBy";

    private final static String DEL_FLAG = "delFlag";

    @Autowired
    private MetaObjectOperator metaObjectOperator;

    private void setMeta(MetaObject metaObject,String field,Object defaultValue){
        if(metaObject.hasGetter(field)){
            Object value = metaObject.getValue(field);
            if(null != value){
                this.setFieldValByName(field,value,metaObject);
            }else {
                this.setFieldValByName(field,defaultValue,metaObject);
            }
        }
    }

    private void setCreateTime(MetaObject metaObject){
        setMeta(metaObject,CREATE_TIME,new Date());
    }

    private void setUpdateTime(MetaObject metaObject){
        setMeta(metaObject,UPDATE_TIME,new Date());
    }

    private void setCreateBy(MetaObject metaObject){
        Object createBy = metaObjectOperator.getCreateBy();
        if(null == createBy){
            return ;
        }
        setMeta(metaObject,CREATE_BY,createBy);
    }

    private void setUpdateBy(MetaObject metaObject){
        Object updateBy = metaObjectOperator.getUpdateBy();
        if(null == updateBy){
            return ;
        }
        setMeta(metaObject,UPDATE_BY,updateBy);
    }

    private void setDelFlag(MetaObject metaObject){
        setMeta(metaObject,DEL_FLAG,0);
    }

    @Override
    public void insertFill(MetaObject metaObject) {
        String name = metaObject.getOriginalObject().getClass().getName();
        if(log.isDebugEnabled()){
            log.debug("{} 自動裝配 createTime、updateTime、createBy、updateBy、delFlag",name);
        }
        setCreateTime(metaObject);
        setUpdateTime(metaObject);
        setCreateBy(metaObject);
        setUpdateBy(metaObject);
        setDelFlag(metaObject);
    }

    @Override
    public void updateFill(MetaObject metaObject) {
        String name = metaObject.getOriginalObject().getClass().getName();
        if(log.isDebugEnabled()){
            log.debug("{} 自動裝配 updateTime、updateBy",name);
        }
        setUpdateTime(metaObject);
        setUpdateBy(metaObject);
    }
}

數據庫讀寫分離

在分佈式縱橫的年代，人們千方百計提升應用程序的性能，將數據庫拆分爲讀寫分離模式【主從複製】是一項提供性能的一種方案。app

固然這種方案只針對對數據一致性沒那麼高要求的程序【弱一致性】。由於在主數據庫同步給從數據庫時候有可能會出現一些額外狀況，如網絡緣由等，致使主從數據庫數據不一致。

本案例採用動態數據源及mybatis-plus來實現讀寫分離

引入依賴

<dependencies>
        <!--mybatis-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.2</version>
        </dependency>
             <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
        </dependency>
      <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>dynamic-datasource-spring-boot-starter</artifactId>
            <version>3.1.1</version>
        </dependency>
    </dependencies>

配置application.yml文件

配置名爲master的主數據庫【用於寫操做】及名爲slave的從數據庫【讀操做】

spring:
  datasource:
    dynamic:
      druid: # 全局druid參數，絕大部分值和默認保持一致。(現已支持的參數以下,不清楚含義不要亂設置)
        # 鏈接池的配置信息
        # 初始化大小，最小，最大
        initial-size: 5
        min-idle: 5
        maxActive: 20
        # 配置獲取鏈接等待超時的時間
        maxWait: 60000
        # 配置間隔多久才進行一次檢測，檢測須要關閉的空閒鏈接，單位是毫秒
        timeBetweenEvictionRunsMillis: 60000
        # 配置一個鏈接在池中最小生存的時間，單位是毫秒
        minEvictableIdleTimeMillis: 300000
        validationQuery: SELECT 1 FROM DUAL
        testWhileIdle: true
        testOnBorrow: false
        testOnReturn: false
        # 打開PSCache，而且指定每一個鏈接上PSCache的大小
        poolPreparedStatements: true
        maxPoolPreparedStatementPerConnectionSize: 20
        # 配置監控統計攔截的filters，去掉後監控界面sql沒法統計，'wall'用於防火牆
        filters: stat,wall,slf4j
        # 經過connectProperties屬性來打開mergeSql功能；慢SQL記錄
        connectionProperties: druid.stat.mergeSql\=true;druid.stat.slowSqlMillis\=5000
      datasource:
        master:
          url: ${MYSQL_URL:jdbc:mysql://localhost:3306/master?characterEncoding=UTF-8&useUnicode=true&useSSL=false}
          username: ${MYSQL_USER:root}
          password: ${MYSQL_PASS:123456}
          driver-class-name: com.mysql.cj.jdbc.Driver
        slave:
          url: ${MYSQL_URL:jdbc:mysql://localhost:3306/slave?characterEncoding=UTF-8&useUnicode=true&useSSL=false}
          username: ${MYSQL_USER:root}
          password: ${MYSQL_PASS:123456}
          driver-class-name: com.mysql.cj.jdbc.Driver

程序使用讀寫分離

顯式使用

只需在對應的方法上加上@DS註解並指明對應的數據源便可

package com.cloud.pango.uc.service.impl;

import com.baomidou.dynamic.datasource.annotation.DS;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.cloud.pango.uc.demo.DemoEntity;
import com.cloud.pango.uc.mapper.DemoMapper;
import com.cloud.pango.uc.service.DemoService;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
public class DemoServiceImpl extends ServiceImpl<DemoMapper, DemoEntity> implements DemoService {

  @DS("master")//標明使用master數據源
  @Override
  public Boolean insert(DemoEntity demo) {
      save(demo);
      return true;
  }

  @DS("slave")//標明使用slave數據源
  @Override
  public DemoEntity findById(String id){
      DemoEntity demo = getById(id);
      return demo;
  }

}

隱式使用

在未使用註解時，使用mybatis-plus攔截器，將讀請求轉移到slave數據源處理，將寫請求轉移到master數據源處理

package com.cloud.pango.uc.common;

import com.baomidou.dynamic.datasource.toolkit.DynamicDataSourceContextHolder;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.transaction.support.TransactionSynchronizationManager;

import java.util.Properties;

@Intercepts({
        @Signature(type = Executor.class, method = "update", args = {
                MappedStatement.class, Object.class }),
        @Signature(type = Executor.class, method = "query", args = {
                MappedStatement.class, Object.class, RowBounds.class,
                ResultHandler.class }) })
@Slf4j
@Component
public class DynamicInterceptor implements Interceptor {

    private static final String MASTER = "master";

    private static final String SLAVE = "slave";

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        boolean synchronizationActive = TransactionSynchronizationManager.isSynchronizationActive();
        if(!synchronizationActive) {
            Object[] objects = invocation.getArgs();
            MappedStatement ms = (MappedStatement) objects[0];
            String currentDataSource = DynamicDataSourceContextHolder.peek();
            if(StringUtils.isEmpty(currentDataSource)){
                if(ms.getSqlCommandType().equals(SqlCommandType.SELECT)) {
                    DynamicDataSourceContextHolder.push(SLAVE);
                }else{
                    DynamicDataSourceContextHolder.push(MASTER);
                }
                Object proceed = invocation.proceed();
                DynamicDataSourceContextHolder.clear();
                return proceed;
            }
        }
        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) {
        if (target instanceof Executor) {
            return Plugin.wrap(target, this);
        } else {
            return target;
        }
    }

    @Override
    public void setProperties(Properties properties) {
    }
}