springboot多數據源讀寫分離和主庫數據源service層事務控制

讀寫分離若是撇開框架無非就是實現多個數據源，主庫用寫的數據源，從庫用讀的數據源。

由於想研究數據庫讀寫分離和分庫分表的設計，因此就本身搭建了一套springboot+druid+mybatis+aop 實現一主多從的設計。
第一步：首先須要自定義數據源的配置項，springboot默認解析的是帶前綴spring.datasource.下面的配置項，爲了避免衝突，就直接定義datasource.當成咱們的前綴，
@ConfigurationProperties(prefix = 「datasource.write」)能夠用來加載指定前綴的配置項，很是方便
由於使用druid，因此須要生成datasource的時候須要指定類型。java

DataSourceBuilder.create().type(dataSourceType).build()

readSize是用來定義從庫的大小，有多少從庫就要配置多少個從庫datasource
第二步：從庫的負載均衡，主要是MyAbstractRoutingDataSource這個類
第三步，從寫springboot-mybatis架包的MybatisAutoConfiguration類的建立SqlSessionFactory方法，將裏面的數據源換成咱們自定義的AbstractRoutingDataSource
第四步驟。自定義事務MyDataSourceTransactionManagerAutoConfigurationmysql

完整代碼和單元測試：
github:https://github.com/ggj2010/javabase.gitgit

主要的架包github

<!-- jdbc driver begin-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <!--mybatis springboot-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>
        <!-- jdbc driver end-->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
        </dependency>

自定義數據源配置項：spring

#多數據源 1主2從
datasource:
 #從庫數量
  readSize: 2
   # 使用druid數據源
  type: com.alibaba.druid.pool.DruidDataSource
#主庫
  write:
    url: jdbc:mysql://localhost:3306/master?useUnicode=true&characterEncoding=utf-8
    username: root
    password: root
    driver-class-name: com.mysql.jdbc.Driver
    filters: stat
    maxActive: 20
    initialSize: 1
    maxWait: 60000
    minIdle: 1
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQueryTimeout: 900000
    validationQuery: SELECT SYSDATE() from dual
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true
    maxOpenPreparedStatements: 20
  read1:
    url: jdbc:mysql://localhost:3306/slave1?useUnicode=true&characterEncoding=utf-8
    username: root
    password: root
    driver-class-name: com.mysql.jdbc.Driver
    filters: stat
    maxActive: 20
    initialSize: 1
    maxWait: 60000
    minIdle: 1
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQueryTimeout: 900000
    validationQuery: SELECT SYSDATE() from dual
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true
    maxOpenPreparedStatements: 20
  read2:
    url: jdbc:mysql://localhost:3306/slave2?useUnicode=true&characterEncoding=utf-8
    username: root
    password: root
    driver-class-name: com.mysql.jdbc.Driver
    filters: stat
    maxActive: 20
    initialSize: 1
    maxWait: 60000
    minIdle: 1
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQueryTimeout: 900000
    validationQuery: SELECT SYSDATE() from dual
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true
    maxOpenPreparedStatements: 20

解析配置項：sql

@Configuration
@Slf4j
public class DataSourceConfiguration {

    @Value("${datasource.type}")
    private Class<? extends DataSource> dataSourceType;

    @Bean(name = "writeDataSource")
    @Primary
    @ConfigurationProperties(prefix = "datasource.write")
    public DataSource writeDataSource() {
        log.info("-------------------- writeDataSource init ---------------------");
        return DataSourceBuilder.create().type(dataSourceType).build();
    }

    /**
     * 有多少個從庫就要配置多少個
     * @return
     */
    @Bean(name = "readDataSource1")
    @ConfigurationProperties(prefix = "datasource.read1")
    public DataSource readDataSourceOne() {
        log.info("-------------------- readDataSourceOne init ---------------------");
        return DataSourceBuilder.create().type(dataSourceType).build();
    }

    @Bean(name = "readDataSource2")
    @ConfigurationProperties(prefix = "datasource.read2")
    public DataSource readDataSourceTwo() {
        log.info("-------------------- readDataSourceTwo init ---------------------");
        return DataSourceBuilder.create().type(dataSourceType).build();
    }
}

重寫SqlSessionFactory數據庫

@Configuration
@AutoConfigureAfter({ DataSourceConfiguration.class })
@Slf4j
public class MybatisConfiguration extends MybatisAutoConfiguration {
    @Value("${datasource.readSize}")
    private String dataSourceSize;

    @Bean
    public SqlSessionFactory sqlSessionFactorys() throws Exception {
        log.info("-------------------- 重載父類 sqlSessionFactory init ---------------------");
        return super.sqlSessionFactory(roundRobinDataSouceProxy());
    }

    /**
     * 有多少個數據源就要配置多少個bean
     * @return
     */
    @Bean
    public AbstractRoutingDataSource roundRobinDataSouceProxy() {
        int size = Integer.parseInt(dataSourceSize);
        MyAbstractRoutingDataSource proxy = new MyAbstractRoutingDataSource(size);
        Map<Object, Object> targetDataSources = new HashMap<Object, Object>();
        DataSource writeDataSource = SpringContextHolder.getBean("writeDataSource");
        // 寫
        targetDataSources.put(DataSourceType.write.getType(), SpringContextHolder.getBean("writeDataSource"));

        for (int i = 0; i < size; i++) {
            targetDataSources.put(i, SpringContextHolder.getBean("readDataSource" + (i + 1)));
        }
        proxy.setDefaultTargetDataSource(writeDataSource);
        proxy.setTargetDataSources(targetDataSources);
        return proxy;
    }

}

本地線程全局變量springboot

public class DataSourceContextHolder {
    private static final ThreadLocal<String> local = new ThreadLocal<String>();

    public static ThreadLocal<String> getLocal() {
        return local;
    }

    /**
     * 讀多是多個庫
     */
    public static void read() {
        local.set(DataSourceType.read.getType());
    }

    /**
     * 寫只有一個庫
     */
    public static void write() {
        local.set(DataSourceType.write.getType());
    }

    public static String getJdbcType() {
        return local.get();
    }
}

多數據源切換mybatis

public class MyAbstractRoutingDataSource extends AbstractRoutingDataSource {
    private final int dataSourceNumber;
    private AtomicInteger count = new AtomicInteger(0);

    public MyAbstractRoutingDataSource(int dataSourceNumber) {
        this.dataSourceNumber = dataSourceNumber;
    }

    @Override
    protected Object determineCurrentLookupKey() {
        String typeKey = DataSourceContextHolder.getJdbcType();
        if (typeKey.equals(DataSourceType.write.getType()))
            return DataSourceType.write.getType();
        // 讀 簡單負載均衡
        int number = count.getAndAdd(1);
        int lookupKey = number % dataSourceNumber;
        return new Integer(lookupKey);
    }
}

enum類型負載均衡

public enum DataSourceType {
    read("read", "從庫"), write("write", "主庫");
    @Getter
    private String type;
    @Getter
    private String name;

    DataSourceType(String type, String name) {
        this.type = type;
        this.name = name;
    }
}

aop攔截設置本地線程變量

@Aspect
@Component
@Slf4j
public class DataSourceAop {

    @Before("execution(* com.ggj.encrypt.modules.*.dao..*.find*(..)) or execution(* com.ggj.encrypt.modules.*.dao..*.get*(..))")
    public void setReadDataSourceType() {
        DataSourceContextHolder.read();
        log.info("dataSource切換到：Read");
    }

    @Before("execution(* com.ggj.encrypt.modules.*.dao..*.insert*(..)) or execution(* com.ggj.encrypt.modules.*.dao..*.update*(..))")
    public void setWriteDataSourceType() {
        DataSourceContextHolder.write();
        log.info("dataSource切換到：write");
    }
}

自定義事務

@Configuration
@EnableTransactionManagement
@Slf4j
public class MyDataSourceTransactionManagerAutoConfiguration extends DataSourceTransactionManagerAutoConfiguration {
    /**
     * 自定義事務
     * MyBatis自動參與到spring事務管理中，無需額外配置，只要org.mybatis.spring.SqlSessionFactoryBean引用的數據源與DataSourceTransactionManager引用的數據源一致便可，不然事務管理會不起做用。
     * @return
     */
    @Bean(name = "transactionManager")
    public DataSourceTransactionManager transactionManagers() {
        log.info("-------------------- transactionManager init ---------------------");
        return new DataSourceTransactionManager(SpringContextHolder.getBean("roundRobinDataSouceProxy"));
    }
}