实现功能
实现基于springmvc+mybatis框架动态切换不同的数据源。
基础框架springmvc4+mybatis3
实现原理
主要利用了spring aop以及spring的AbstractRoutingDataSource类。
AbstractRoutingDataSource
通过观察源码，可以抽取该类中几个重要元素
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;
}
通过解读源码，可以知道，targetDataSources用来初始化预存的数据源，defaultTargetDataSource则是默认数据源，当determineTargetDataSource获取不到用户定义的数据源时，使用该默认数据源。在determineTargetDataSource中通过determineCurrentLookupKey来获取自定义数据源的KEY，这也正是我们要复写的方法。
如果每次方法调用都去手动切换数据源，一方面代码耦合度高，另一方面可维护性可扩展性差，因此我们利用spring aop编写pointcut去执行动态切换。
具体配置
spring配置文件(部分)
<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="${jdbc.master.c3p0.preferred_test_query}" />
</bean>
<bean id="mysqlDataSource2" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close">
<property name="driverClass" value="${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>
<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>
<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>
......
<aop:aspectj-autoproxy/>
<bean id="dataSourceAspect" class="com.test.aspect.DataSourceAspect"></bean>
......
jdbc配置文件如下
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
自定义注解类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()
}
数据源控制类DynamicDataSource、DynamicDataSourceHolder
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
public class DynamicDataSource extends AbstractRoutingDataSource {
@Override
protected Object
determineCurrentLookupKey() {
return DynamicDataSourceHolder.getDataSourceType();
}
}
public class DynamicDataSourceHolder {
private static final ThreadLocal<String> contextHolder =
new ThreadLocal();
public static void setDataSourceType(String dataSourceType) {
contextHolder.
set(dataSourceType);
}
public static String
getDataSourceType() {
return (String) contextHolder.
get();
}
public static void clearDataSourceType() {
contextHolder.remove();
}
}
切面类DataSourceAspect ，用于控制切换，切入点为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()
}
}
测试用的service，用于查询权限
编写一个测试用例
/**
*
* <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);
}
}
这里controller和mybatis的配置代码就不给出了，具体业务系统自己编写，测试数据中1库有数据，2库为空，最后测试效果如下：
