實現功能

實現基於springmvc+mybatis框架動態切換不同的資料來源。

基礎框架springmvc4+mybatis3

實現原理

主要利用了spring aop以及spring的AbstractRoutingDataSource類。

AbstractRoutingDataSource

通過觀察原始碼，可以抽取該類中幾個重要元素

properties:

    private Map<Object, Object> targetDataSources;

    private Object defaultTargetDataSource;
 

functions:

@Override
    public void afterPropertiesSet() {
        if (this.targetDataSources == null) {
            throw new IllegalArgumentException("Property 'targetDataSources' is required");
        }
        this.resolvedDataSources = new HashMap<Object, DataSource>(this.targetDataSources.size());
        for
 
 (Map.Entry<Object, Object> entry : this.targetDataSources.entrySet()) {
            Object lookupKey = resolveSpecifiedLookupKey(entry.getKey());
            DataSource dataSource = resolveSpecifiedDataSource(entry.getValue());
            this.resolvedDataSources.put(lookupKey, dataSource);
        }
        if
 
 (this.defaultTargetDataSource != null) {
            this.resolvedDefaultDataSource = resolveSpecifiedDataSource(this.defaultTargetDataSource);
        }
    }
public Connec

tion getConnection() throws SQLException {
        return determineTargetDataSource().getConnection();
    }

protected DataSource determineTargetDataSource() {
        Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
        Object lookupKey = determineCurrentLookupKey();
        DataSource dataSource = this.resolvedDataSources.get(lookupKey);
        if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
            dataSource = this.resolvedDefaultDataSource;
        }
        if (dataSource == null) {
            throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
        }
        return dataSource;
    }

通過解讀原始碼，可以知道，targetDataSources用來初始化預存的資料來源，defaultTargetDataSource則是預設資料來源，當determineTargetDataSource獲取不到使用者定義的資料來源時，使用該預設資料來源。在determineTargetDataSource中通過determineCurrentLookupKey來獲取自定義資料來源的KEY，這也正是我們要複寫的方法。

如果每次方法呼叫都去手動切換資料來源，一方面程式碼耦合度高，另一方面可維護性可擴充套件性差，因此我們利用spring aop編寫pointcut去執行動態切換。

具體配置

spring配置檔案(部分)

<!-- 主資料來源 1-->
    <bean id="mysqlDataSource1" class="com.mchange.v2.c3p0.ComboPooledDataSource"
        destroy-method="close">
        <property name="driverClass" value="${jdbc.master.driverClassName}" />
        <property name="jdbcUrl" value="${jdbc.master.url}" />
        <property name="user" value="${jdbc.master.username}" />
        <property name="password" value="${jdbc.master.password}" />
        <property name="initialPoolSize" value="${jdbc.master.c3p0.initialPoolSize}" />
        <property name="minPoolSize" value="${jdbc.master.c3p0.min_size}" />
        <property name="maxPoolSize" value="${jdbc.master.c3p0.max_size}" />
        <property name="maxIdleTime" value="${jdbc.master.c3p0.max_idle_time}" />
        <property name="acquireIncrement" value="${jdbc.master.c3p0.acquire_increment}" />
        <property name="maxStatements" value="${jdbc.master.c3p0.max_statements}" />
        <property name="idleConnectionTestPeriod" value="${jdbc.master.c3p0.idle_connection_test_period}" />
        <property name="checkoutTimeout" value="${jdbc.master.c3p0.checkout_timeout}" />
        <property name="testConnectionOnCheckin" value="${jdbc.master.c3p0.test_connection_on_checkin}" />
        <property name="automaticTestTable" value="${jdbc.master.c3p0.automatic_test_table}" />
        <property name="preferredTestQuery" value="${jdbc.master.c3p0.preferred_test_query}" />
    </bean>


    <!-- 從資料來源 2-->
    <bean id="mysqlDataSource2" class="com.mchange.v2.c3p0.ComboPooledDataSource"
        destroy-method="close">
        <property name="driverClass" value="${jdbc.slave.driverClassName}" />
        <property name="jdbcUrl" value="${jdbc.slave.url}" />
        <property name="user" value="${jdbc.slave.username}" />
        <property name="password" value="${jdbc.slave.password}" />
        <property name="initialPoolSize" value="${jdbc.slave.c3p0.initialPoolSize}" />
        <property name="minPoolSize" value="${jdbc.slave.c3p0.min_size}" />
        <property name="maxPoolSize" value="${jdbc.slave.c3p0.max_size}" />
        <property name="maxIdleTime" value="${jdbc.slave.c3p0.max_idle_time}" />
        <property name="acquireIncrement" value="${jdbc.slave.c3p0.acquire_increment}" />
        <property name="maxStatements" value="${jdbc.slave.c3p0.max_statements}" />
        <property name="idleConnectionTestPeriod" value="${jdbc.slave.c3p0.idle_connection_test_period}" />
        <property name="checkoutTimeout" value="${jdbc.slave.c3p0.checkout_timeout}" />
        <property name="testConnectionOnCheckin" value="${jdbc.slave.c3p0.test_connection_on_checkin}" />
        <property name="automaticTestTable" value="${jdbc.slave.c3p0.automatic_test_table}" />
        <property name="preferredTestQuery" value="${jdbc.slave.c3p0.preferred_test_query}" />
    </bean>

    <!-- 多資料來源配置 -->
    <bean id="dataSource" class="com.test.tools.DynamicDataSource">  
        <property name="targetDataSources">  
            <map key-type="java.lang.String">  
                <entry value-ref="mysqlDataSource1" key="mysqlDataSource1"></entry>  
                <entry value-ref="mysqlDataSource2" key="mysqlDataSource2"></entry>  
            </map>  
        </property>  
        <property name="defaultTargetDataSource" ref="mysqlDataSource1"></property>  
    </bean>

    <!-- sessionfactory1 -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean" lazy-init="false" >
        <property name="configLocation" value="classpath:/mybatis/mybatis-config.xml" />
        <property name="mapperLocations" value="classpath*:/mybatis/mappers/*.xml" />
        <property name="dataSource" ref="dataSource" />
    </bean>

    <bean name="mapperConf" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="annotationClass" value="org.springframework.stereotype.Repository" />
        <property name="basePackage" value="com.**.dao" />
    </bean>

......

 <!--使用aspectj建立aop  -->
   <aop:aspectj-autoproxy/>
   <bean id="dataSourceAspect" class="com.test.aspect.DataSourceAspect"></bean>

  ......

jdbc配置檔案如下

jdbc.master.driverClassName=com.mysql.jdbc.Driver
jdbc.master.url=jdbc:mysql://127.0.0.1:3360/test2?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
jdbc.master.username=root
jdbc.master.password=Landi12345
jdbc.master.c3p0.acquire_increment=2
jdbc.master.c3p0.initialPoolSize=2
jdbc.master.c3p0.min_size=2
jdbc.master.c3p0.max_size=10
jdbc.master.c3p0.max_idle_time=180
jdbc.master.c3p0.max_statements=0
jdbc.master.c3p0.idle_connection_test_period=180
jdbc.master.c3p0.checkout_timeout=30000
jdbc.master.c3p0.test_connection_on_checkin=true
jdbc.master.c3p0.automatic_test_table=c3p0_test
jdbc.master.c3p0.preferred_test_query=select * from "c3p0_test"


jdbc.slave.driverClassName=com.mysql.jdbc.Driver
jdbc.slave.url=jdbc:mysql://127.0.0.1:3306/test2?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
jdbc.slave.username=root
jdbc.slave.password=Landi123456
jdbc.slave.c3p0.acquire_increment=2
jdbc.slave.c3p0.initialPoolSize=2
jdbc.slave.c3p0.min_size=2
jdbc.slave.c3p0.max_size=10
jdbc.slave.c3p0.max_idle_time=180
jdbc.slave.c3p0.max_statements=0
jdbc.slave.c3p0.idle_connection_test_period=180
jdbc.slave.c3p0.checkout_timeout=30000
jdbc.slave.c3p0.test_connection_on_checkin=true
jdbc.slave.c3p0.automatic_test_table=c3p0_test
jdbc.slave.c3p0.preferred_test_query=select * from "c3p0_test"


jdbc.transation_timeout=1800

自定義註解類DataSource

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.TYPE,ElementType.METHOD})  
@Retention(RetentionPolicy.RUNTIME)  
public @interface DataSource {  
    String value();  
}  

資料來源控制類DynamicDataSource、DynamicDataSourceHolder

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

public class DynamicDataSource extends AbstractRoutingDataSource {    
    @Override  
    protected Object determineCurrentLookupKey() {  
        return DynamicDataSourceHolder.getDataSourceType();  
    }  

} 

public class DynamicDataSourceHolder {
    // 執行緒區域性變數（多執行緒併發設計，為了執行緒安全）
    private static final ThreadLocal<String> contextHolder = new ThreadLocal();  

    // 設定資料來源型別  
    public static void setDataSourceType(String dataSourceType) {  
        contextHolder.set(dataSourceType);  
    }  

    // 獲取資料來源型別  
    public static String getDataSourceType() {  
        return (String) contextHolder.get();  
    }  

    // 清除資料來源型別  
    public static void clearDataSourceType() {  
        contextHolder.remove();  
    }

}

切面類DataSourceAspect ，用於控制切換，切入點為service

import org.apache.log4j.Logger;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;

import com.test.tools.DynamicDataSourceHolder;
import com.test.utils.DataSource;

@Aspect
public class DataSourceAspect {
    private final static Logger log = Logger.getLogger(DataSourceAspect.class);


    @Before("execution(* com.test.service..*.*(..))&&@annotation(ds)")
    public void changeDataSource(JoinPoint point, DataSource ds) throws Throwable {
        String key = ds.value();
        if(key!=null && !key.trim().equals("")){
            DynamicDataSourceHolder.setDataSourceType(key);
        }
    }

    @After("execution(* com.test.service..*.*(..))&&@annotation(ds)")
    public void restoreDataSource(JoinPoint point, DataSource ds) {
        DynamicDataSourceHolder.clearDataSourceType();
    }
}

測試用的service，用於查詢許可權

編寫一個測試用例

/**
 * 
 * <br>
 * <b>功能：</b>SysAuthoService<br>
 */
@Service("sysauthoService")
public class  SysAuthoServiceImpl  extends BaseServiceImpl implements SysAuthoService {
  private final static Logger log= Logger.getLogger(SysAuthoServiceImpl.class);


    @Resource
    private SysAuthoDao dao;


    public SysAuthoDao getDao() {
        return dao;
    }

    @DataSource(value="mysqlDataSource1")
    @Override
    public List<ListBean> readWebList(SysAutho queryObj) {
        return dao.readWebList(queryObj);
    }

    @DataSource(value="mysqlDataSource2")
    @Override
    public List<ListBean> readWebList2(SysAutho queryObj) {
        return dao.readWebList2(queryObj);
    }

}

這裡controller和mybatis的配置程式碼就不給出了，具體業務系統自己編寫，測試資料中1庫有資料，2庫為空，最後測試效果如下：