关键字：springcloud、mybatis、多数据源负载均衡、拦截器动态分页
配置文件是通过springcloudconfig远程分布式配置。采用阿里Druid数据源。并支持一主多从的读写分离。分页组件通过拦截器拦截带有page后缀的方法名，动态的设置total总数。
1. 解析配置文件初始化数据源
@Configuration
public class DataSourceConfiguration {
/**
* 数据源类型
*/
@Value("${spring.datasource.type}")
private Class<? extends DataSource> dataSourceType;
/**
* 主数据源配置
*
* @return
*/
@Bean(name = "masterDataSource", destroyMethod = "close")
@Primary
@ConfigurationProperties(prefix = "spring.datasource")
public DataSource masterDataSource() {
DataSource source = DataSourceBuilder.create().type(dataSourceType).build();
return source;
}
/**
* 从数据源配置
*
* @return
*/
@Bean(name = "slaveDataSource0")
@ConfigurationProperties(prefix = "spring.slave0")
public DataSource slaveDataSource0() {
DataSource source = DataSourceBuilder.create().type(dataSourceType).build();
return source;
}
/**
* 从数据源集合
*
* @return
*/
@Bean(name = "slaveDataSources")
public List<DataSource> slaveDataSources() {
List<DataSource> slaveDataSources = new ArrayList();
slaveDataSources.add(slaveDataSource0());
return slaveDataSources;
}
}
2. 定义数据源枚举类型
public enum DataSourceType {
master("master", "master"), slave("slave", "slave");
private String type;
private String name;
DataSourceType(String type, String name) {
this.type = type;
this.name = name;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
3. TheadLocal保存数据源类型
public class DataSourceContextHolder {
private static final ThreadLocal<String> local = new ThreadLocal<String>();
public static ThreadLocal<String> getLocal() {
return local;
}
public static void slave() {
local.set(DataSourceType.slave.getType());
}
public static void master() {
local.set(DataSourceType.master.getType());
}
public static String getJdbcType() {
return local.get();
}
public static void clearDataSource(){
local.remove();
}
}
4. 自定义sqlSessionProxy，并将数据源填充到DataSourceRoute
@Configuration
@ConditionalOnClass({EnableTransactionManagement.class})
@Import({DataSourceConfiguration.class})
public class DataSourceSqlSessionFactory {
private Logger logger = Logger.getLogger(DataSourceSqlSessionFactory.class);
@Value("${spring.datasource.type}")
private Class<? extends DataSource> dataSourceType;
@Value("${mybatis.mapper-locations}")
private String mapperLocations;
@Value("${mybatis.type-aliases-package}")
private String aliasesPackage;
@Value("${slave.datasource.number}")
private int dataSourceNumber;
@Resource(name = "masterDataSource")
private DataSource masterDataSource;
@Resource(name = "slaveDataSources")
private List<DataSource> slaveDataSources;
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory() throws Exception {
logger.info("======================= init sqlSessionFactory");
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(roundRobinDataSourceProxy());
PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
sqlSessionFactoryBean.setMapperLocations(resolver.getResources(mapperLocations));
sqlSessionFactoryBean.setTypeAliasesPackage(aliasesPackage);
sqlSessionFactoryBean.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);
return sqlSessionFactoryBean.getObject();
}
@Bean(name = "roundRobinDataSourceProxy")
public AbstractRoutingDataSource roundRobinDataSourceProxy() {
logger.info("======================= init robinDataSourceProxy");
DataSourceRoute proxy = new DataSourceRoute(dataSourceNumber);
Map<Object, Object> targetDataSources = new HashMap();
targetDataSources.put(DataSourceType.master.getType(), masterDataSource);
if(null != slaveDataSources) {
for(int i=0; i<slaveDataSources.size(); i++){
targetDataSources.put(i, slaveDataSources.get(i));
}
}
proxy.setDefaultTargetDataSource(masterDataSource);
proxy.setTargetDataSources(targetDataSources);
return proxy;
}
}
5. 自定义路由
public class DataSourceRoute extends AbstractRoutingDataSource {
private Logger logger = Logger.getLogger(DataSourceRoute.class);
private final int dataSourceNumber;
public DataSourceRoute(int dataSourceNumber) {
this.dataSourceNumber = dataSourceNumber;
}
@Override
protected Object determineCurrentLookupKey() {
String typeKey = DataSourceContextHolder.getJdbcType();
logger.info("==================== swtich dataSource:" + typeKey);
if (typeKey.equals(DataSourceType.master.getType())) {
return DataSourceType.master.getType();
}else{
//从数据源随机分配
Random random = new Random();
int slaveDsIndex = random.nextInt(dataSourceNumber);
return slaveDsIndex;
}
}
}
6. 定义切面，dao层定义切面
@Aspect
@Component
public class DataSourceAop {
private Logger logger = Logger.getLogger(DataSourceAop.class);
@Before("execution(* com.dbq.iot.mapper..*.get*(..)) || execution(* com.dbq.iot.mapper..*.isExist*(..)) " +
"|| execution(* com.dbq.iot.mapper..*.select*(..)) || execution(* com.dbq.iot.mapper..*.count*(..)) " +
"|| execution(* com.dbq.iot.mapper..*.list*(..)) || execution(* com.dbq.iot.mapper..*.query*(..))" +
"|| execution(* com.dbq.iot.mapper..*.find*(..))|| execution(* com.dbq.iot.mapper..*.search*(..))")
public void setSlaveDataSourceType(JoinPoint joinPoint) {
DataSourceContextHolder.slave();
logger.info("=========slave, method:" + joinPoint.getSignature().getName());
}
@Before("execution(* com.dbq.iot.mapper..*.add*(..)) || execution(* com.dbq.iot.mapper..*.del*(..))" +
"||execution(* com.dbq.iot.mapper..*.upDate*(..)) || execution(* com.dbq.iot.mapper..*.insert*(..))" +
"||execution(* com.dbq.iot.mapper..*.create*(..)) || execution(* com.dbq.iot.mapper..*.update*(..))" +
"||execution(* com.dbq.iot.mapper..*.delete*(..)) || execution(* com.dbq.iot.mapper..*.remove*(..))" +
"||execution(* com.dbq.iot.mapper..*.save*(..)) || execution(* com.dbq.iot.mapper..*.relieve*(..))" +
"|| execution(* com.dbq.iot.mapper..*.edit*(..))")
public void setMasterDataSourceType(JoinPoint joinPoint) {
DataSourceContextHolder.master();
logger.info("=========master, method:" + joinPoint.getSignature().getName());
}
}
7. 最后在写库增加事务管理
@Configuration
@Import({DataSourceConfiguration.class})
public class DataSouceTranscation extends DataSourceTransactionManagerAutoConfiguration {
private Logger logger = Logger.getLogger(DataSouceTranscation.class);
@Resource(name = "masterDataSource")
private DataSource masterDataSource;
/**
* 配置事务管理器
*
* @return
*/
@Bean(name = "transactionManager")
public DataSourceTransactionManager transactionManagers() {
logger.info("===================== init transactionManager");
return new DataSourceTransactionManager(masterDataSource);
}
}
8. 在配置文件中增加数据源配置
spring.datasource.name=writedb
spring.datasource.url=jdbc:mysql://192.168.0.1/master?useUnicode=true&characterEncoding=utf8&autoReconnect=true&failOverReadOnly=false
spring.datasource.username=root
spring.datasource.password=1234
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.filters=stat
spring.datasource.initialSize=20
spring.datasource.minIdle=20
spring.datasource.maxActive=200
spring.datasource.maxWait=60000
#从库的数量
slave.datasource.number=1
spring.slave0.name=readdb
spring.slave0.url=jdbc:mysql://192.168.0.2/slave?useUnicode=true&characterEncoding=utf8&autoReconnect=true&failOverReadOnly=false
spring.slave0.username=root
spring.slave0.password=1234
spring.slave0.type=com.alibaba.druid.pool.DruidDataSource
spring.slave0.driver-class-name=com.mysql.jdbc.Driver
spring.slave0.filters=stat
spring.slave0.initialSize=20
spring.slave0.minIdle=20
spring.slave0.maxActive=200
spring.slave0.maxWait=60000
这样就实现了在springcloud框架下的读写分离，并且支持多个从库的负载均衡（简单的通过随机分配，也有网友通过算法实现平均分配，具体做法是通过一个线程安全的自增长Integer类型，取余实现。个人觉得没大必要。如果有大神有更好的方法可以一起探讨。）
Mabatis分页配置可通过dao层的拦截器对特定方法进行拦截，拦截后添加自己的逻辑代码，比如计算total等，具体代码如下（参考了网友的代码，主要是通过@Intercepts注解）：
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class PageInterceptor implements Interceptor {
private static final Log logger = LogFactory.getLog(PageInterceptor.class);
private static final ObjectFactory DEFAULT_OBJECT_FACTORY = new DefaultObjectFactory();
private static final ObjectWrapperFactory DEFAULT_OBJECT_WRAPPER_FACTORY = new DefaultObjectWrapperFactory();
private static final ReflectorFactory DEFAULT_REFLECTOR_FACTORY = new DefaultReflectorFactory();
private static String defaultDialect = "mysql"; // 数据库类型(默认为mysql)
private static String defaultPageSqlId = ".*Page$"; // 需要拦截的ID(正则匹配)
private String dialect = ""; // 数据库类型(默认为mysql)
private String pageSqlId = ""; // 需要拦截的ID(正则匹配)
@Override
public Object intercept(Invocation invocation) throws Throwable {
StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
MetaObject metaStatementHandler = MetaObject.forObject(statementHandler, DEFAULT_OBJECT_FACTORY,
DEFAULT_OBJECT_WRAPPER_FACTORY,DEFAULT_REFLECTOR_FACTORY);
// 分离代理对象链(由于目标类可能被多个拦截器拦截，从而形成多次代理，通过下面的两次循环可以分离出最原始的的目标类)
while (metaStatementHandler.hasGetter("h")) {
Object object = metaStatementHandler.getValue("h");
metaStatementHandler = MetaObject.forObject(object, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY,DEFAULT_REFLECTOR_FACTORY);
}
// 分离最后一个代理对象的目标类
while (metaStatementHandler.hasGetter("target")) {
Object object = metaStatementHandler.getValue("target");
metaStatementHandler = MetaObject.forObject(object, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY,DEFAULT_REFLECTOR_FACTORY);
}
Configuration configuration = (Configuration) metaStatementHandler.getValue("delegate.configuration");
if (null == dialect || "".equals(dialect)) {
logger.warn("Property dialect is not setted,use default 'mysql' ");
dialect = defaultDialect;
}
if (null == pageSqlId || "".equals(pageSqlId)) {
logger.warn("Property pageSqlId is not setted,use default '.*Page$' ");
pageSqlId = defaultPageSqlId;
}
MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
// 只重写需要分页的sql语句。通过MappedStatement的ID匹配，默认重写以Page结尾的MappedStatement的sql
if (mappedStatement.getId().matches(pageSqlId)) {
BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
Object parameterObject = boundSql.getParameterObject();
if (parameterObject == null) {
throw new NullPointerException("parameterObject is null!");
} else {
PageParameter page = (PageParameter) metaStatementHandler
.getValue("delegate.boundSql.parameterObject.page");
String sql = boundSql.getSql();
// 重写sql
String pageSql = buildPageSql(sql, page);
metaStatementHandler.setValue("delegate.boundSql.sql", pageSql);
metaStatementHandler.setValue("delegate.rowBounds.offset", RowBounds.NO_ROW_OFFSET);
metaStatementHandler.setValue("delegate.rowBounds.limit", RowBounds.NO_ROW_LIMIT);
Connection connection = (Connection) invocation.getArgs()[0];
// 重设分页参数里的总页数等
setPageParameter(sql, connection, mappedStatement, boundSql, page);
}
}
// 将执行权交给下一个拦截器
return invocation.proceed();
}
/**
* @param sql
* @param connection
* @param mappedStatement
* @param boundSql
* @param page
*/
private void setPageParameter(String sql, Connection connection, MappedStatement mappedStatement,
BoundSql boundSql, PageParameter page) {
// 记录总记录数
String countSql = "select count(0) from (" + sql + ") as total";
PreparedStatement countStmt = null;
ResultSet rs = null;
try {
countStmt = connection.prepareStatement(countSql);
BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(), countSql,
boundSql.getParameterMappings(), boundSql.getParameterObject());
Field metaParamsField = ReflectUtil.getFieldByFieldName(boundSql, "metaParameters");
if (metaParamsField != null) {
try {
MetaObject mo = (MetaObject) ReflectUtil.getValueByFieldName(boundSql, "metaParameters");
ReflectUtil.setValueByFieldName(countBS, "metaParameters", mo);
} catch (SecurityException | NoSuchFieldException | IllegalArgumentException
| IllegalAccessException e) {
// TODO Auto-generated catch block
logger.error("Ignore this exception", e);
}
}
Field additionalField = ReflectUtil.getFieldByFieldName(boundSql, "additionalParameters");
if (additionalField != null) {
try {
Map<String, Object> map = (Map<String, Object>) ReflectUtil.getValueByFieldName(boundSql, "additionalParameters");
ReflectUtil.setValueByFieldName(countBS, "additionalParameters", map);
} catch (SecurityException | NoSuchFieldException | IllegalArgumentException
| IllegalAccessException e) {
// TODO Auto-generated catch block
logger.error("Ignore this exception", e);
}
}
setParameters(countStmt, mappedStatement, countBS, boundSql.getParameterObject());
rs = countStmt.executeQuery();
int totalCount = 0;
if (rs.next()) {
totalCount = rs.getInt(1);
}
page.setTotalCount(totalCount);
int totalPage = totalCount / page.getPageSize() + ((totalCount % page.getPageSize() == 0) ? 0 : 1);
page.setTotalPage(totalPage);
} catch (SQLException e) {
logger.error("Ignore this exception", e);
} finally {
try {
if (rs != null){
rs.close();
}
} catch (SQLException e) {
logger.error("Ignore this exception", e);
}
try {
if (countStmt != null){
countStmt.close();
}
} catch (SQLException e) {
logger.error("Ignore this exception", e);
}
}
}
/**
* 对SQL参数(?)设值
*
* @param ps
* @param mappedStatement
* @param boundSql
* @param parameterObject
* @throws SQLException
*/
private void setParameters(PreparedStatement ps, MappedStatement mappedStatement, BoundSql boundSql,
Object parameterObject) throws SQLException {
ParameterHandler parameterHandler = new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);
parameterHandler.setParameters(ps);
}
/**
* 根据数据库类型，生成特定的分页sql
*
* @param sql
* @param page
* @return
*/
private String buildPageSql(String sql, PageParameter page) {
if (page != null) {
StringBuilder pageSql = new StringBuilder();
pageSql = buildPageSqlForMysql(sql,page);
return pageSql.toString();
} else {
return sql;
}
}
/**
* mysql的分页语句
*
* @param sql
* @param page
* @return String
*/
public StringBuilder buildPageSqlForMysql(String sql, PageParameter page) {
StringBuilder pageSql = new StringBuilder(100);
String beginrow = String.valueOf((page.getCurrentPage() - 1) * page.getPageSize());
pageSql.append(sql);
pageSql.append(" limit " + beginrow + "," + page.getPageSize());
return pageSql;
}
@Override
public Object plugin(Object target) {
if (target instanceof StatementHandler) {
return Plugin.wrap(target, this);
} else {
return target;
}
}
@Override
public void setProperties(Properties properties) {
}
}
这里碰到一个比较有趣的问题，就是sql如果是foreach参数，在拦截后无法注入。需要加入以下代码才可以（有得资料上只提到重置metaParameters）。
Field metaParamsField = ReflectUtil.getFieldByFieldName(boundSql, "metaParameters");
if (metaParamsField != null) {
try {
MetaObject mo = (MetaObject) ReflectUtil.getValueByFieldName(boundSql, "metaParameters");
ReflectUtil.setValueByFieldName(countBS, "metaParameters", mo);
} catch (SecurityException | NoSuchFieldException | IllegalArgumentException
| IllegalAccessException e) {
// TODO Auto-generated catch block
logger.error("Ignore this exception", e);
}
}
Field additionalField = ReflectUtil.getFieldByFieldName(boundSql, "additionalParameters");
if (additionalField != null) {
try {
Map<String, Object> map = (Map<String, Object>) ReflectUtil.getValueByFieldName(boundSql, "additionalParameters");
ReflectUtil.setValueByFieldName(countBS, "additionalParameters", map);
} catch (SecurityException | NoSuchFieldException | IllegalArgumentException
| IllegalAccessException e) {
// TODO Auto-generated catch block
logger.error("Ignore this exception", e);
}
}
读写分离倒是写好了，但是发现增加了mysql一主多从的读写分离后，此分页拦截器直接失效。
最后分析原因是因为，我们在做主从分离时，自定义了SqlSessionFactory，导致此拦截器没有注入。
在上面第4步中，DataSourceSqlSessionFactory中注入拦截器即可，具体代码如下
通过注解引入拦截器类：
@Import({DataSourceConfiguration.class,PageInterceptor.class})
注入拦截器
@Autowired
private PageInterceptor pageInterceptor;
SqlSessionFactoryBean中设置拦截器
sqlSessionFactoryBean.setPlugins(newInterceptor[]{pageInterceptor});
这里碰到一个坑，就是设置plugins时必须在sqlSessionFactoryBean.getObject()之前。
SqlSessionFactory在生成的时候就会获取plugins，并设置到Configuration中，如果在之后设置则不会注入。
可跟踪源码看到：
sqlSessionFactoryBean.getObject()
public SqlSessionFactory getObject() throws Exception {
if (this.sqlSessionFactory == null) {
afterPropertiesSet();
}
return this.sqlSessionFactory;
}
public void afterPropertiesSet() throws Exception {
notNull(dataSource, "Property 'dataSource' is required");
notNull(sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");
state((configuration == null && configLocation == null) || !(configuration != null && configLocation != null),
"Property 'configuration' and 'configLocation' can not specified with together");
this.sqlSessionFactory = buildSqlSessionFactory();
}
buildSqlSessionFactory()
if (!isEmpty(this.plugins)) {
for (Interceptor plugin : this.plugins) {
configuration.addInterceptor(plugin);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Registered plugin: '" + plugin + "'");
}
}
}
最后贴上正确的配置代码(DataSourceSqlSessionFactory代码片段)
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory() throws Exception {
logger.info("======================= init sqlSessionFactory");
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setPlugins(new Interceptor[]{pageInterceptor});
sqlSessionFactoryBean.setDataSource(roundRobinDataSourceProxy());
PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
sqlSessionFactoryBean.setMapperLocations(resolver.getResources(mapperLocations));
sqlSessionFactoryBean.setTypeAliasesPackage(aliasesPackage);
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBean.getObject();
sqlSessionFactory.getConfiguration().setMapUnderscoreToCamelCase(true);
return sqlSessionFactory;
}
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