扩展Myabatis Pagehelper支持多数据源的分页插件

http://git.oschina.net/free/Mybatis_PageHelper/blob/master/wikis/Important.markdown

结合spring使用mybatis pagehelper只能配置一个bean，当一个项目使用多种数据库时就比较纠结了，下面是我参考spring支持多数据源的思想封装一个支持多数据源的PageHelper。

实现一个mybatis插件，参考mybatis pagehelper，实现根据不同的数据源切换使用不同的pagehelper。

@SuppressWarnings({"rawtypes", "unchecked"})
@Intercepts(@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}))
public class CustomPageHelper implements Interceptor {

private PageHelper mysqlPageHelper = new PageHelper();

private PageHelper oraclePageHelper = new PageHelper();

private PageHelper postgresqlPageHelper = new PageHelper();

private Map<Object, PageHelper> targetPageHelper = new HashMap<>();

private PageHelper defaultPageHelper;

@Override
public Object intercept(Invocation invocation) throws Throwable {
return determinePageHelper().intercept(invocation);
}

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

@Override
public void setProperties(Properties properties) {
targetPageHelper.put(Dialect.mysql.name(), mysqlPageHelper);
targetPageHelper.put(Dialect.oracle.name(), oraclePageHelper);
targetPageHelper.put(Dialect.postgresql.name(), postgresqlPageHelper);
//数据库方言
String dialect = properties.getProperty("dialect");
if(Dialect.oracle.equals(Dialect.valueOf(dialect.toLowerCase()))) {
defaultPageHelper = oraclePageHelper;
} else if(Dialect.postgresql.equals(Dialect.valueOf(dialect.toLowerCase()))) {
defaultPageHelper = postgresqlPageHelper;
} else {
defaultPageHelper = mysqlPageHelper;
}

properties.put("dialect", Dialect.mysql.name());
mysqlPageHelper.setProperties(properties);

properties.put("dialect", Dialect.oracle.name());
oraclePageHelper.setProperties(properties);

properties.put("dialect", Dialect.postgresql.name());
postgresqlPageHelper.setProperties(properties);

properties.put("dialect", dialect);
}

private PageHelper determinePageHelper() {
String pageType = PageHelperHolder.getPagerType();
PageHelper pageHelper = targetPageHelper.get(pageType);
if (pageHelper != null) {
return pageHelper;
} else {
return defaultPageHelper;
}
}
}

<!-- Oracle配置数据源-->
<bean id="oracleDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close">
<property name="driverClass" value="${oracle.jdbc.driver}"/>
<property name="jdbcUrl" value="${oracle.jdbc.url}"/>
<property name="user" value="${oracle.jdbc.user}"/>
<property name="password" value="${oracle.jdbc.password}"/>
<property name="minPoolSize" value="${oracle.jdbc.minPoolSize}"/>
<property name="maxPoolSize" value="${oracle.jdbc.maxPoolSize}"/>
<property name="initialPoolSize" value="${oracle.jdbc.initialPoolSize}"/>
<property name="maxIdleTime" value="${oracle.jdbc.maxIdleTime}"/>
<property name="acquireIncrement" value="${oracle.jdbc.acquireIncrement}"/>
<property name="acquireRetryAttempts" value="${oracle.jdbc.acquireRetryAttempts}"/>
<property name="acquireRetryDelay" value="${oracle.jdbc.acquireRetryDelay}"/>
<property name="testConnectionOnCheckin" value="${oracle.jdbc.testConnectionOnCheckin}"/>
<property name="automaticTestTable" value="${oracle.jdbc.automaticTestTable}"/>
<property name="idleConnectionTestPeriod" value="${oracle.jdbc.idleConnectionTestPeriod}"/>
<property name="checkoutTimeout" value="${oracle.jdbc.checkoutTimeout}"/>
</bean>

<!-- Mysql配置数据源-->
<bean id="mysqlDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close">
<property name="driverClass" value="${mysql.jdbc.driver}"/>
<property name="jdbcUrl" value="${mysql.jdbc.url}"/>
<property name="user" value="${mysql.jdbc.user}"/>
<property name="password" value="${mysql.jdbc.password}"/>
<property name="minPoolSize" value="${mysql.jdbc.minPoolSize}"/>
<property name="maxPoolSize" value="${mysql.jdbc.maxPoolSize}"/>
<property name="initialPoolSize" value="${mysql.jdbc.initialPoolSize}"/>
<property name="maxIdleTime" value="${mysql.jdbc.maxIdleTime}"/>
<property name="acquireIncrement" value="${mysql.jdbc.acquireIncrement}"/>
<property name="acquireRetryAttempts" value="${mysql.jdbc.acquireRetryAttempts}"/>
<property name="acquireRetryDelay" value="${mysql.jdbc.acquireRetryDelay}"/>
<property name="testConnectionOnCheckin" value="${mysql.jdbc.testConnectionOnCheckin}"/>
<property name="automaticTestTable" value="${mysql.jdbc.automaticTestTable}"/>
<property name="idleConnectionTestPeriod" value="${mysql.jdbc.idleConnectionTestPeriod}"/>
<property name="checkoutTimeout" value="${mysql.jdbc.checkoutTimeout}"/>
</bean>

<bean id="pgDataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
<!-- 基本属性 url、user、password -->
<property name="driverClassName" value="${pg.db.drivername}"/>
<property name="url" value="${pg.db.url}" />
<property name="username" value="${pg.db.username}" />
<property name="password" value="${pg.db.password}" />
<property name="dbType" value="postgresql" />

<!-- 配置初始化大小、最小、最大 -->
<property name="initialSize" value="1" />
<property name="minIdle" value="1" />
<property name="maxActive" value="50" />

<!-- 配置获取连接等待超时的时间 -->
<property name="maxWait" value="60000" />

<!-- 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒 -->
<property name="timeBetweenEvictionRunsMillis" value="60000" />

<!-- 配置一个连接在池中最小生存的时间，单位是毫秒 -->
<property name="minEvictableIdleTimeMillis" value="300000" />

<property name="validationQuery" value="SELECT 1" />
<property name="testWhileIdle" value="true" />
<property name="testOnBorrow" value="false" />
<property name="testOnReturn" value="true" />

<!-- 打开PSCache，并且指定每个连接上PSCache的大小 -->
<property name="poolPreparedStatements" value="true" />
<property name="maxPoolPreparedStatementPerConnectionSize" value="20" />

<!-- 配置监控统计拦截的filters -->
<property name="filters" value="stat" />
</bean>

<bean id="multipleDataSource" class="com.common.support.MultipleDataSource">
<property name="defaultTargetDataSource" ref="mysqlDataSource"/>
<property name="targetDataSources">
<map>
<entry key="mySqlDataSource" value-ref="mysqlDataSource"/>
<entry key="passSqlDataSource" value-ref="passsqlDataSource"/>
<entry key="oracleDataSource" value-ref="oracleDataSource"/>
<entry key="greenplumDataSource" value-ref="greenplumDataSource"/>
</map>
</property>
</bean>

<!-- 配置sql会话工厂：SqlSessionFactoryBean -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="multipleDataSource" />
<!--<property name="dataSource" ref="oracleDataSource"/>-->
<property name="plugins">
<array>
<bean class="com.common.support.CustomPageHelper" scope="singleton">
<property name="properties">
<value>dialect=mysql</value>
</property>
</bean>
</array>
</property>
</bean>

最后定义一个PageHelperHolder，在数据源切换时把当前使用的数据库类型放进来以为Pagehelper动态切换数据源。

public final class PageHelperHolder {
//    public enum PagerType {
//        MySql, Oracle
//    }
private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();

public static void setPagerType(Dialect Dialect) {
contextHolder.set(Dialect.name());
}

public static String getPagerType() {
return contextHolder.get();
}

public static void clearPaerType() {
contextHolder.remove();
}
}

自定义注解，用来加到mapper上面，aop拦截mybatis mapper方法时根据注解来判断数据源类型从而决定用哪个分页

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
@Documented
public @interface DataSourceSelector {
DataSourceType value();
}

public enum DataSourceType {
MYSQL_DATASOURCE("mySqlDataSource", Dialect.mysql),
ORACLE_DATASOURCE("oracleDataSource", Dialect.oracle),
GREENPLUM_DATASOURCE("pgDataSource", Dialect.postgresql),

private String type;
private Dialect dialect;

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

public String getType() {
return type;
}

public Dialect getDialect() {
return dialect;
}

public static DataSourceType getType(String type) {
for(DataSourceType dataSourceType : DataSourceType.values()) {
if(dataSourceType.type.equals(type)) {
return dataSourceType;
}
}
return null;
}
}

下面是spring aop拦截mapper的重点代码片段

@Aspect
public class MultipleDataSourceAspectAdvice {
@Around("execution(* com.mapper.*.*(..))")
public Object doAround(ProceedingJoinPoint jp) throws Throwable {
return DataSourceHolder.getDynaDataSource(jp);
}
}

//做mapper使用数据源类型缓存，不用每次都要从注解中读取
private transient static Map<Class, String> dataSourceHolder = new HashMap<>();
public static Object getDynaDataSource(ProceedingJoinPoint jp) throws Throwable {
Object result = null;
Class targetClass = jp.getThis().getClass();
try {
log.debug("MultipleDataSourceAspectAdvice: {}, {}", jp.getThis(), jp.getTarget());
//获取我们写的mapper类，以便读取到类上面的注解
Class[] interfaces = targetClass.getInterfaces();
if (interfaces != null && interfaces.length > 0) {
targetClass = interfaces[0];
}
String targetDataSource = dataSourceHolder.get(targetClass);
boolean isHold = false;
if (StringUtils.isBlank(targetDataSource)) {
//读取注解上声明要使用的数据源类型
DataSourceSelector dss = (DataSourceSelector) targetClass.getAnnotation(DataSourceSelector.class);
if (dss != null) {
targetDataSource = dss.value().getType();
}
} else {
isHold = true;
}

if (StringUtils.isNotBlank(targetDataSource)) {
DataSourceType dataSourceType = DataSourceType.getType(targetDataSource);
if(dataSourceType != null) {
DataSourceHolder.setCustomerType(dataSourceType.getType());
PageHelperHolder.setPagerType(dataSourceType.getDialect());
if (!isHold) {
dataSourceHolder.put(targetClass, targetDataSource);
}
} else {
log.warn("{}-{} not found available dataSourceType, use default.", targetClass, targetDataSource);
}
}
log.debug("{}: {}", targetClass, dataSourceHolder.get(targetClass));
result = jp.proceed();
} catch (Exception ex) {
log.error("deal with dynamic datasource error. datasource: {}", DataSourceHolder.getCustomerType());
dataSourceHolder.remove(targetClass);
throw ex;
} finally {
DataSourceHolder.clearCustomerType();
PageHelperHolder.clearPaerType();
}

return result;
}

mapper类

@DataSourceSelector(DataSourceType.MYSQL_DATASOURCE)
public interface SysRoleMapper {
……
}

大体实现就是这样子了，要注意的是spring数据源的配置bean的id和DataSourceType中定义的名称了一致，要不然key不一样会取不到哦。