spring实现动态维护数据源（动态增加或动态删除）
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最近在做spring3+mybatis3整合，网上搜索了很多技术文章，都是实现动态切换数据源、或者是动态配置多数据源的，这里先声明一下，本文里面介绍的是运行时的动态维护，可以在系统运行期间动态增减数据源、并且可以根据需要切换数据源，笔者顺便鄙视下一些所谓开源的“大公司”的“大牛们”！
系统有一个默认的datasource（这个数据源是通过spring进行配置的），在这个datasource中维护了一张datasource表，用来维护其他的数据源（DynamicDataSource），表结构如下：
动态数据源DynamicDataSource在spring的applicationContext.xml配置文件中定义如下：
线程安全的ThreadLocal:DBContextHolder.java
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/**
* @author williams
* @descrice 多个登录用户可能需要同时切换数据源，所以这里需要写一个线程安全的ThreadLocal
* @more 用户切换数据源只要在程序中使用 DBContextHolder.setDBType("1") 即可完成数据源切换
*/
public class DBContextHolder {
private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();
public static void setDBType(String dbType) {
contextHolder.set(dbType);
}
public static String getDBType() {
return (String) contextHolder.get();
}
public static void clearDBType() {
contextHolder.remove();
}
}
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实现动态数据源切换逻辑
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import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.dbcp.BasicDataSource;
import org.apache.log4j.Logger;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
/**
* @author williams
* @describe 实现动态数据源切换逻辑
*/
public class DynamicDataSource extends AbstractRoutingDataSource {
private Logger log = Logger.getLogger(this.getClass());
private Map<Object, Object> _targetDataSources;
/**
* @see org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource#determineCurrentLookupKey()
* @describe 数据源为空或者为0时，自动切换至默认数据源，即在配置文件中定义的dataSource数据源
*/
@Override
protected Object determineCurrentLookupKey() {
String dataSourceName = DBContextHolder.getDBType();
if (dataSourceName == null) {
dataSourceName = "dataSource";
} else {
this.selectDataSource(Integer.valueOf(dataSourceName));
if (dataSourceName.equals("0"))
dataSourceName = "dataSource";
}
log.debug("--------> use datasource " + dataSourceName);
return dataSourceName;
}
public void setTargetDataSources(Map<Object, Object> targetDataSources) {
this._targetDataSources = targetDataSources;
super.setTargetDataSources(this._targetDataSources);
afterPropertiesSet();
}
public void addTargetDataSource(String key, BasicDataSource dataSource) {
this._targetDataSources.put(key, dataSource);
this.setTargetDataSources(this._targetDataSources);
}
public BasicDataSource createDataSource(String driverClassName, String url,
String username, String password) {
BasicDataSource dataSource = new BasicDataSource();
dataSource.setDriverClassName(driverClassName);
dataSource.setUrl(url);
dataSource.setUsername(username);
dataSource.setPassword(password);
dataSource.setTestWhileIdle(true);
return dataSource;
}
/**
* @param serverId
* @describe 数据源存在时不做处理，不存在时创建新的数据源链接，并将新数据链接添加至缓存
*/
public void selectDataSource(Integer serverId) {
Object sid = DBContextHolder.getDBType();
if ("0".equals(serverId + "")) {
DBContextHolder.setDBType("0");
return;
}
Object obj = this._targetDataSources.get(serverId);
if (obj != null && sid.equals(serverId + "")) {
return;
} else {
BasicDataSource dataSource = this.getDataSource(serverId);
if (null != dataSource)
this.setDataSource(serverId, dataSource);
}
}
/**
* @describe 查询serverId对应的数据源记录
* @param serverId
*
@return
*/
public BasicDataSource getDataSource(Integer serverId) {
this.selectDataSource(0);
this.determineCurrentLookupKey();
Connection conn = null;
HashMap<String, Object> map = null;
try {
conn = this.getConnection();
PreparedStatement ps = conn
.prepareStatement("SELECT * FROM bas_datasource WHERE DBS_ID = ?");
ps.setInt(1, serverId);
ResultSet rs = ps.executeQuery();
map = new HashMap<String, Object>();
if (rs.next()) {
map.put("DBS_ID", rs.getInt("DBS_ID"));
map.put("DBS_DriverClassName", rs
.getString("DBS_DriverClassName"));
map.put("DBS_URL", rs.getString("DBS_URL"));
map.put("DBS_UserName", rs.getString("DBS_UserName"));
map.put("DBS_Password", rs.getString("DBS_Password"));
}
rs.close();
ps.close();
} catch (SQLException e) {
log.error(e);
} finally {
try {
conn.close();
} catch (SQLException e) {
log.error(e);
}
}
if (null != map) {
String driverClassName = map.get("DBS_DriverClassName").toString();
String url = map.get("DBS_URL").toString();
String userName = map.get("DBS_UserName").toString();
String password = map.get("DBS_Password").toString();
BasicDataSource dataSource = this.createDataSource(driverClassName,
url, userName, password);
return dataSource;
}
return null;
}
/**
* @param serverId
* @param dataSource
*/
public void setDataSource(Integer serverId, BasicDataSource dataSource) {
this.addTargetDataSource(serverId + "", dataSource);
DBContextHolder.setDBType(serverId + "");
}
}
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