上一篇文章介绍了 spring-boot整合mybatis+druid连接池实现多数据源,在这个例子中我们为每个DataSource都初始化一个与之对应的SessionFactory,从而实现连接化多个数据源。再仔细体会一下,会发现这种方式有一点静态的味道。
在实际需求中,我们经常会遇到mysql的读写分离、冷热分离等需求,这种情况虽然也可以看成多数据源的一种情况,用上面的方式去处理,但是有没有更好的解决方法呢?
答案是:有。我们可以设计一种数据源动态切换的架构,整个系统中就初始化一个SessionFactory,设计一个DynamicDataSource类,把所有数据源放进去,然后根据不同需求动态的切换数据源,实现mysql的读写分离、冷热分离。。。
基于这种方式,不仅可是实现真正意义上的多数据源的切换(第二种实现多数据源的思路),还可以实现在程序的运行过程中,实现动态添加一个或多个新的数据源。这里重点关注的是配置文件之间的关系,对象模型如下:
首先分析一下AbstractRoutingDataSource抽象类的源码:
public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean { private Map<Object, Object> targetDataSources; private Object defaultTargetDataSource; private boolean lenientFallback = true; private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup(); private Map<Object, DataSource> resolvedDataSources; private DataSource resolvedDefaultDataSource; public AbstractRoutingDataSource() { } public void setTargetDataSources(Map<Object, Object> targetDataSources) { this.targetDataSources = targetDataSources; } public void setDefaultTargetDataSource(Object defaultTargetDataSource) { this.defaultTargetDataSource = defaultTargetDataSource; } public void setLenientFallback(boolean lenientFallback) { this.lenientFallback = lenientFallback; } public void setDataSourceLookup(DataSourceLookup dataSourceLookup) { this.dataSourceLookup = (DataSourceLookup)(dataSourceLookup != null ? dataSourceLookup : new JndiDataSourceLookup()); } public void afterPropertiesSet() { if (this.targetDataSources == null) { throw new IllegalArgumentException("Property 'targetDataSources' is required"); } else { this.resolvedDataSources = new HashMap(this.targetDataSources.size()); Iterator var1 = this.targetDataSources.entrySet().iterator(); while(var1.hasNext()) { Entry<Object, Object> entry = (Entry)var1.next(); Object lookupKey = this.resolveSpecifiedLookupKey(entry.getKey()); DataSource dataSource = this.resolveSpecifiedDataSource(entry.getValue()); this.resolvedDataSources.put(lookupKey, dataSource); } if (this.defaultTargetDataSource != null) { this.resolvedDefaultDataSource = this.resolveSpecifiedDataSource(this.defaultTargetDataSource); } } } protected Object resolveSpecifiedLookupKey(Object lookupKey) { return lookupKey; } protected DataSource resolveSpecifiedDataSource(Object dataSource) throws IllegalArgumentException { if (dataSource instanceof DataSource) { return (DataSource)dataSource; } else if (dataSource instanceof String) { return this.dataSourceLookup.getDataSource((String)dataSource); } else { throw new IllegalArgumentException("Illegal data source value - only [javax.sql.DataSource] and String supported: " + dataSource); } } public Connection getConnection() throws SQLException { return this.determineTargetDataSource().getConnection(); } public Connection getConnection(String username, String password) throws SQLException { return this.determineTargetDataSource().getConnection(username, password); } public <T> T unwrap(Class<T> iface) throws SQLException { return iface.isInstance(this) ? this : this.determineTargetDataSource().unwrap(iface); } public boolean isWrapperFor(Class<?> iface) throws SQLException { return iface.isInstance(this) || this.determineTargetDataSource().isWrapperFor(iface); } protected DataSource determineTargetDataSource() { Assert.notNull(this.resolvedDataSources, "DataSource router not initialized"); Object lookupKey = this.determineCurrentLookupKey(); DataSource 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 + "]"); } else { return dataSource; } } protected abstract Object determineCurrentLookupKey(); }对于该抽象类,关注两组变量:
Map<Object, Object> targetDataSources
和
Object defaultTargetDataSource
、
Map<Object, DataSource> resolvedDataSources
和
DataSource resolvedDefaultDataSource
;这两组变量是相互对应的;在熟悉多实例数据源切换代码的不难发现,当有多个数据源的时候,一定要指定一个作为默认的数据源,在这里也同理,当同时初始化多个数据源的时候,需要显示的调用setDefaultTargetDataSource方法指定一个作为默认数据源;
我们需要关注的是Map<Object, Object> targetDataSources
和Map<Object, DataSource> resolvedDataSources
,targetDataSources是暴露给外部程序用来赋值的,而resolvedDataSources是程序内部执行时的依据,因此会有一个赋值的操作,如下图所示:
根据这段源码可以看出,每次执行时,都会遍历targetDataSources内的所有元素并赋值给resolvedDataSources;这样如果我们在外部程序新增一个新的数据源,都会添加到内部使用,从而实现数据源的动态加载。
继承该抽象类的时候,必须实现一个抽象方法:protected abstract Object determineCurrentLookupKey()
,该方法用于指定到底需要使用哪一个数据源。
到此基本上清楚了该抽象类的使用方法,接下来贴下具体的实现代码。
1、pom.xml
同上一篇文章中的pom;
2、application.properties和数据源配置:
1)application.properties
#---------------------使用durid连接池 ds1.w.datasource.url=jdbc:mysql://jy.ttengine.w.abc.db:1883/ttengine?useUnicode=true&characterEncoding=utf8 ds1.w.datasource.username=ttengine ds1.w.datasource.password=TTengine123 ds1.w.datasource.driverClassName=com.mysql.jdbc.Driver ds1.r.datasource.url=jdbc:mysql://jy.ttengine.r.abc.db:1883/ttengine?useUnicode=true&characterEncoding=utf8 ds1.r.datasource.username=ttengine ds1.r.datasource.password=TTengine123 ds1.r.datasource.driverClassName=com.mysql.jdbc.Driver ds1.datasource.initialSize=20 ds1.datasource.minIdle=20 ds1.datasource.maxActive=200 ds1.datasource.maxWait=60000 ds1.datasource.timeBetweenEvictionRunsMillis=60000 ds1.datasource.minEvictableIdleTimeMillis=300000 ds1.datasource.testWhileIdle=true ds1.datasource.testOnBorrow=false ds1.datasource.testOnReturn=false ds1.datasource.poolPreparedStatements=true ds1.datasource.maxPoolPreparedStatementPerConnectionSize=20 # 页面默认前缀目录 spring.mvc.view.prefix=/WEB-INF/page/ spring.mvc.view.suffix=.jsp
2)自定义数据源切换类:
package cn.edu.nuc.Test1.dao.mysql.config; public class DatabaseContextHolder { private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>(); public static void setDBKey(String dataSourceKey) { contextHolder.set(dataSourceKey); } public static String getDBKey() { return contextHolder.get(); } public static void clearDBKey() { contextHolder.remove(); } }
通过ThreadLocal维护一个全局唯一的map来实现数据源的动态切换。
3)自定义DynamicDataSource:
package cn.edu.nuc.Test1.dao.mysql.config; import java.util.HashMap; import java.util.Map; import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource; /** * 动态数据源 * @author kevinliu * */ public class DynamicDataSource extends AbstractRoutingDataSource { private static DynamicDataSource instance; private static byte[] lock=new byte[0]; private static Map<Object,Object> dataSourceMap=new HashMap<Object, Object>(); @Override public void setTargetDataSources(Map<Object, Object> targetDataSources) { super.setTargetDataSources(targetDataSources); dataSourceMap.putAll(targetDataSources); super.afterPropertiesSet();// 必须添加该句,否则新添加数据源无法识别到 } public Map<Object, Object> getDataSourceMap() { return dataSourceMap; } @Override protected Object determineCurrentLookupKey() { String dbKey = DatabaseContextHolder.getDBKey(); /*if (StringUtils.isBlank(dbKey)) { dbKey = "read"; }*/ return dbKey; } private DynamicDataSource() {} public static synchronized DynamicDataSource getInstance(){ if(instance==null){ synchronized (lock){ if(instance==null){ instance=new DynamicDataSource(); } } } return instance; } }
该类有以下几个方法:
- 私有构造方法和获取单例的方法;
- 实现了抽象类的determineCurrentLookupKey方法,从上面的map中获取数据源,然后动态切换;
- 覆盖了抽象类的setTargetDataSources方法,主要用来动态创建数据源,然后动态切换;
4)定制DataSourceConfig:
package cn.edu.nuc.Test1.dao.mysql.config; import java.sql.SQLException; import java.util.HashMap; import java.util.Map; import javax.sql.DataSource; import org.apache.ibatis.session.SqlSessionFactory; import org.mybatis.spring.SqlSessionFactoryBean; import org.mybatis.spring.annotation.MapperScan; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.beans.factory.annotation.Value; import org.springframework.boot.web.servlet.FilterRegistrationBean; import org.springframework.boot.web.servlet.ServletRegistrationBean; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.core.io.support.PathMatchingResourcePatternResolver; import org.springframework.jdbc.datasource.DataSourceTransactionManager; import com.alibaba.druid.pool.DruidDataSource; import com.alibaba.druid.support.http.StatViewServlet; import com.alibaba.druid.support.http.WebStatFilter; @Configuration //扫描 Mapper 接口并容器管理 @MapperScan(basePackages = DatasourceConfig.PACKAGE, sqlSessionFactoryRef = "sqlSessionFactory") public class DatasourceConfig { // 精确到 master 目录,以便跟其他数据源隔离 static final String PACKAGE = "cn.edu.nuc.Test1.dao.mysql"; static final String MAPPER_LOCATION = "classpath:mapper/*.xml"; @Value("${ds1.w.datasource.url}") private String wurl; @Value("${ds1.w.datasource.username}") private String wuser; @Value("${ds1.w.datasource.password}") private String wpassword; @Value("${ds1.w.datasource.driverClassName}") private String wdriverClass; @Value("${ds1.r.datasource.url}") private String rurl; @Value("${ds1.r.datasource.username}") private String ruser; @Value("${ds1.r.datasource.password}") private String rpassword; @Value("${ds1.r.datasource.driverClassName}") private String rdriverClass; @Value("${ds1.datasource.maxActive}") private Integer maxActive; @Value("${ds1.datasource.minIdle}") private Integer minIdle; @Value("${ds1.datasource.initialSize}") private Integer initialSize; @Value("${ds1.datasource.maxWait}") private Long maxWait; @Value("${ds1.datasource.timeBetweenEvictionRunsMillis}") private Long timeBetweenEvictionRunsMillis; @Value("${ds1.datasource.minEvictableIdleTimeMillis}") private Long minEvictableIdleTimeMillis; @Value("${ds1.datasource.testWhileIdle}") private Boolean testWhileIdle; @Value("${ds1.datasource.testWhileIdle}") private Boolean testOnBorrow; @Value("${ds1.datasource.testOnBorrow}") private Boolean testOnReturn; @Bean(name = "dynamicDataSource") public DynamicDataSource dynamicDataSource() { DynamicDataSource dynamicDataSource = DynamicDataSource.getInstance(); //jdbc配置 DruidDataSource wdataSource = new DruidDataSource(); wdataSource.setDriverClassName(wdriverClass); wdataSource.setUrl(wurl); wdataSource.setUsername(wuser); wdataSource.setPassword(wpassword); //连接池配置 wdataSource.setMaxActive(maxActive); wdataSource.setMinIdle(minIdle); wdataSource.setInitialSize(initialSize); wdataSource.setMaxWait(maxWait); wdataSource.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis); wdataSource.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis); wdataSource.setTestWhileIdle(testWhileIdle); wdataSource.setTestOnBorrow(testOnBorrow); wdataSource.setTestOnReturn(testOnReturn); wdataSource.setValidationQuery("SELECT 'x'"); wdataSource.setPoolPreparedStatements(true); wdataSource.setMaxPoolPreparedStatementPerConnectionSize(20); try { wdataSource.setFilters("stat"); } catch (SQLException e) { e.printStackTrace(); } //jdbc配置 DruidDataSource rdataSource = new DruidDataSource(); rdataSource.setDriverClassName(rdriverClass); rdataSource.setUrl(rurl); rdataSource.setUsername(ruser); rdataSource.setPassword(rpassword); //连接池配置 rdataSource.setMaxActive(maxActive); rdataSource.setMinIdle(minIdle); rdataSource.setInitialSize(initialSize); rdataSource.setMaxWait(maxWait); rdataSource.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis); rdataSource.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis); rdataSource.setTestWhileIdle(testWhileIdle); rdataSource.setTestOnBorrow(testOnBorrow); rdataSource.setTestOnReturn(testOnReturn); rdataSource.setValidationQuery("SELECT 'x'"); rdataSource.setPoolPreparedStatements(true); rdataSource.setMaxPoolPreparedStatementPerConnectionSize(20); try { rdataSource.setFilters("stat"); } catch (SQLException e) { e.printStackTrace(); } Map<Object,Object> map = new HashMap<>(); map.put("ds1_w", wdataSource); map.put("ds1_r", rdataSource); dynamicDataSource.setTargetDataSources(map); dynamicDataSource.setDefaultTargetDataSource(rdataSource); return dynamicDataSource; } @Bean(name = "transactionManager") public DataSourceTransactionManager transactionManager() { return new DataSourceTransactionManager(dynamicDataSource()); } @Bean(name = "sqlSessionFactory") public SqlSessionFactory sqlSessionFactory(@Qualifier("dynamicDataSource") DataSource dynamicDataSource) throws Exception { final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean(); sessionFactory.setDataSource(dynamicDataSource); sessionFactory.setTypeAliasesPackage("cn.edu.nuc.Test1.entity"); sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver() .getResources(DatasourceConfig.MAPPER_LOCATION)); return sessionFactory.getObject(); } @Bean public ServletRegistrationBean druidServlet() { ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean(); servletRegistrationBean.setServlet(new StatViewServlet()); servletRegistrationBean.addUrlMappings("/druid/*"); Map<String, String> initParameters = new HashMap<String, String>(); initParameters.put("loginUsername", "admin");// 用户名 initParameters.put("loginPassword", "admin");// 密码 initParameters.put("resetEnable", "false");// 禁用HTML页面上的“Reset All”功能 initParameters.put("allow", ""); // IP白名单 (没有配置或者为空,则允许所有访问) //initParameters.put("deny", "192.168.20.38");// IP黑名单 (存在共同时,deny优先于allow) servletRegistrationBean.setInitParameters(initParameters); return servletRegistrationBean; } @Bean public FilterRegistrationBean filterRegistrationBean() { FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(); filterRegistrationBean.setFilter(new WebStatFilter()); filterRegistrationBean.addUrlPatterns("/*"); filterRegistrationBean.addInitParameter("exclusions", "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*"); return filterRegistrationBean; } }
该类和上一篇文章中的略有不同:
- 获取数据源时返回的是自定义DynamicDataSource(继承了AbstractRoutingDataSource抽象类),在其方法上,创建读和写两个DruidDataSource对象,然后放到了DynamicDataSource中;此外,下面只创建了一个sessionFactory对象;
- 在创建好DruidSource后,调用下面两个方法初始化数据源:dynamicDataSource.setTargetDataSources(map);dynamicDataSource.setDefaultTargetDataSource(rdataSource);
3、其他:
动态数据源配置好后,接下来就和正常spring-boot的用法一样了。整个结构:
1)crontroller:
package cn.edu.nuc.Test1.controller; import javax.servlet.http.HttpServletRequest; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.ResponseBody; import cn.edu.nuc.Test1.entity.Test; import cn.edu.nuc.Test1.service.TestService; @Controller public class TestController { private static final Logger logger = LoggerFactory.getLogger(TestController.class); @Autowired private TestService testService; @RequestMapping("/test") @ResponseBody public String test(HttpServletRequest request) { String name = request.getParameter("name"); Test test = null; try { test = testService.findByName(name); } catch (Exception e) { test = new Test(); logger.error("test error.",e); } logger.info("test....{}",name); return test.toString(); } @RequestMapping("/save") @ResponseBody public String saveTest(HttpServletRequest request) { String res = "0"; String name = request.getParameter("name"); try { testService.saveTest(name); } catch (Exception e) { res = "1"; logger.error("save test error.",e); } logger.info("save test....{}",name); return res; } }
两个方法:一个读方法(连接从库),一个写方法(连接主库)
2)service:
package cn.edu.nuc.Test1.service; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import cn.edu.nuc.Test1.dao.mysql.TestDao; import cn.edu.nuc.Test1.dao.mysql.config.DatabaseContextHolder; import cn.edu.nuc.Test1.entity.Test; @Service public class TestService{ private static final Logger logger = LoggerFactory.getLogger(TestService.class); @Autowired private TestDao testDao; public Test findByName(String name) throws Exception{ logger.info("findByName..."); return testDao.findByName(name); } public void saveTest(String name) throws Exception{ logger.info("saveTest..."); DatabaseContextHolder.setDBKey("ds1_w"); Test t = new Test(); t.setName(name); testDao.saveTest(t); } }
3)entity:
package cn.edu.nuc.Test1.entity; public class Test { private Long id; private String name; public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "Test [id=" + id + ", name=" + name + "]"; } }
4)dao:
package cn.edu.nuc.Test1.dao.mysql; import org.apache.ibatis.annotations.Param; import cn.edu.nuc.Test1.entity.Test; public interface TestDao { Test findByName(@Param("name") String n) throws Exception; void saveTest(Test t) throws Exception; }
5)mapper文件:
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" > <mapper namespace="cn.edu.nuc.Test1.dao.mysql.TestDao"> <resultMap id="BaseResultMap" type="cn.edu.nuc.Test1.entity.Test"> <result column="id" property="id" /> <result column="name" property="name" /> </resultMap> <parameterMap id="Test" type="cn.edu.nuc.Test1.entity.Test"/> <sql id="Base_Column_List"> id,name </sql> <select id="findByName" resultMap="BaseResultMap" parameterType="java.lang.String"> select <include refid="Base_Column_List" /> from test where name = #{name} </select> <!-- 插入 --> <insert id="saveTest" parameterType="Test"> insert into test (name) values (#{name}) </insert> </mapper>
6)主类:
package cn.edu.nuc.Test1; import org.mybatis.spring.annotation.MapperScan; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; /** * Hello world! * 可以统一用@MapperScan指定扫描的dao,也可以在每个dao上添加@Mapper */ @SpringBootApplication //mapper 接口类扫描包配置 @MapperScan("cn.edu.nuc.Test1.dao.mysql") public class App { public static void main( String[] args ) { SpringApplication.run(App.class, args); } }参考:https://blog.csdn.net/YHYR_YCY/article/details/78894940