Spring动态数据源路由实现

本文介绍如何使用Spring的AbstractRoutingDataSource实现根据不同用户级别动态切换数据源的方法。通过定义多个数据源,并利用枚举类型作为键值,实现了基于用户级别的数据源路由。此外,还展示了具体的配置示例和测试案例。

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在Spring 2.0.1中引入了AbstractRoutingDataSource, 该类充当了DataSource的路由中介, 能有在运行时, 根据某种key值来动态切换到真正的DataSource上, 同时对于不支持事务隔离级别的JTA事务来说, Spring还提供了另外一个类IsolationLevelDataSourceRouter来处理这个问题. 下面的例子将通过context来切换不同的数据源.

首先定义一个Catalog的Dao:

package blog.datasource;

 

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.List;

 

import org.springframework.jdbc.core.simple.ParameterizedRowMapper;

import org.springframework.jdbc.core.simple.SimpleJdbcDaoSupport;

 

public class Catalog extends SimpleJdbcDaoSupport {

 

    public List<Item> getItems() {

        String query = "select name, price from item";

        return getSimpleJdbcTemplate().query(query, new ParameterizedRowMapper<Item>() {

            public Item mapRow(ResultSet rs, int row) throws SQLException {

                String name = rs.getString(1);

                double price = rs.getDouble(2);

                return new Item(name, price);

            }

        });

    }

}

 

然后定义一个Item的JavaBean

package blog.datasource;

 

public class Item {

 

   private String name;

   private double price;

       

   public Item(String name, double price) {

      this.name = name;

      this.price = price;

   }

 

   public String getName() {

      return name;

   }

 

   public double getPrice() {

      return price;

   }

 

   public String toString() {

      return name + " (" + price + ")";

   }

}

接着定义一个枚举类型, 用来表示不同的用户级别, 通过该类型将映射到不同的数据源

package blog.datasource;

public enum CustomerType {

   BRONZE,

   SILVER,

   GOLD

}

下面是DataSource定义:

<bean id="parentDataSource"

    class="org.springframework.jdbc.datasource.DriverManagerDataSource"

    abstract="true">

    <property name="driverClassName" value="org.hsqldb.jdbcDriver" />

    <property name="username" value="sa" />

</bean>

<bean id="goldDataSource" parent="parentDataSource">

    <property name="url"

        value="jdbc:hsqldb:hsql://localhost:${db.port.gold}/blog" />

</bean>

<bean id="silverDataSource" parent="parentDataSource">

    <property name="url"

        value="jdbc:hsqldb:hsql://localhost:${db.port.silver}/blog" />

</bean>

<bean id="bronzeDataSource" parent="parentDataSource">

    <property name="url"

        value="jdbc:hsqldb:hsql://localhost:${db.port.bronze}/blog" />

</bean>

<bean

    class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">

    <property name="location"

        value="classpath:/blog/datasource/db.properties" />

</bean>

AbstractRoutingDataSource 实现类

package blog.datasource;

 

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

 

public class CustomerRoutingDataSource extends AbstractRoutingDataSource {

 

    @Override

    protected Object determineCurrentLookupKey() {

        return CustomerContextHolder.getCustomerType();

    }

}

CustomerContextHolder 是一个和LocalThread绑定的类, 定义如下:

public class CustomerContextHolder {

 

    private static final ThreadLocal<CustomerType> contextHolder = new ThreadLocal<CustomerType>();

 

    public static void setCustomerType(CustomerType customerType) {

        Assert.notNull(customerType, "customerType cannot be null");

        contextHolder.set(customerType);

    }

 

    public static CustomerType getCustomerType() {

        return (CustomerType) contextHolder.get();

    }

 

    public static void clearCustomerType() {

        contextHolder.remove();

    }

}

将dao bean和datasource bean结合起来, 至于dao和真正的datasource如何关联这个可以根据需要指定相关的策略和规则来实现:

<bean id="catalog" class="blog.datasource.Catalog">

    <property name="dataSource" ref="dataSource" />

</bean>

<bean id="dataSource"

    class="blog.datasource.CustomerRoutingDataSource">

    <property name="targetDataSources">

        <map key-type="blog.datasource.CustomerType">

            <entry key="GOLD" value-ref="goldDataSource" />

            <entry key="SILVER" value-ref="silverDataSource" />

        </map>

    </property>

    <property name="defaultTargetDataSource" ref="bronzeDataSource" />

</bean>

下面通过一个TestCase来看看如何使用:

public class CatalogTests extends AbstractDependencyInjectionSpringContextTests {

 

    private Catalog catalog;

 

    public void setCatalog(Catalog catalog) {

        this.catalog = catalog;

    }

 

    public void testDataSourceRouting() {

        CustomerContextHolder.setCustomerType(CustomerType.GOLD);

        List<Item> goldItems = catalog.getItems();

        assertEquals(3, goldItems.size());

        System.out.println("gold items: " + goldItems);

 

        CustomerContextHolder.setCustomerType(CustomerType.SILVER);

        List<Item> silverItems = catalog.getItems();

        assertEquals(2, silverItems.size());

        System.out.println("silver items: " + silverItems);

 

        CustomerContextHolder.clearCustomerType();

        List<Item> bronzeItems = catalog.getItems();

        assertEquals(1, bronzeItems.size());

        System.out.println("bronze items: " + bronzeItems);

    }

 

    protected String[] getConfigLocations() {

        return new String[] { "/blog/datasource/beans.xml" };

    }

}

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