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NodeList ruleNodes = e.getElementsByTagName("rule");
int length = ruleNodes.getLength();
if (length > 1) {
throw new ConfigException("only one rule can defined :"
+ name);
}
//目前只处理第一个，未来可能有多列复合逻辑需求
//RuleConfig是保存着rule与function对应关系的对象
RuleConfig rule = loadRule((Element) ruleNodes.item(0));
String funName = rule.getFunctionName();
//判断function是否存在，获取function
AbstractPartitionAlgorithm func = functions.get(funName);
if (func == null) {
throw new ConfigException("can't find function of name :"
+ funName);
}
rule.setRuleAlgorithm(func);
//保存到tableRules
tableRules.put(name, new TableRuleConfig(name, rule));
}
}
}这样，所有的tableRule和function就加载完毕。保存在一个变量中，就是tableRules：XMLRuleLoader.java:
private final Map<String, TableRuleConfig> tableRules;
4.2 schema.xml:
public XMLSchemaLoader(String schemaFile, String ruleFile) { //先读取rule.xml
XMLRuleLoader ruleLoader = new XMLRuleLoader(ruleFile); //将tableRules拿出，用于这里加载Schema做rule有效判断，以及之后的分片路由计算
this.tableRules = ruleLoader.getTableRules(); //释放ruleLoader
ruleLoader = null; this.dataHosts = new HashMap<String, DataHostConfig>(); this.dataNodes = new HashMap<String, DataNodeConfig>(); this.schemas = new HashMap<String, SchemaConfig>(); //读取加载schema配置
this.load(DEFAULT_DTD, schemaFile == null ? DEFAULT_XML : schemaFile);
}private void load(String dtdFile, String xmlFile) {
InputStream dtd = null;
InputStream xml = null; try {
dtd = XMLSchemaLoader.class.getResourceAsStream(dtdFile);
xml = XMLSchemaLoader.class.getResourceAsStream(xmlFile);
Element root = ConfigUtil.getDocument(dtd, xml).getDocumentElement(); //先加载所有的DataHost
loadDataHosts(root); //再加载所有的DataNode
loadDataNodes(root); //最后加载所有的Schema
loadSchemas(root);
} catch (ConfigException e) { throw e;
} catch (Exception e) { throw new ConfigException(e);
} finally { if (dtd != null) { try {
dtd.close();
} catch (IOException e) {
}
} if (xml != null) { try {
xml.close();
} catch (IOException e) {
}
}
}
}先看下DataHostConfig这个类的结构： 
private void loadDataHosts(Element root) {
NodeList list = root.getElementsByTagName("dataHost"); for (int i = 0, n = list.getLength(); i < n; ++i) {
Element element = (Element) list.item(i);
String name = element.getAttribute("name"); //判断是否重复
if (dataHosts.containsKey(name)) { throw new ConfigException("dataHost name " + name + "duplicated!");
} //读取最大连接数
int maxCon = Integer.valueOf(element.getAttribute("maxCon")); //读取最小连接数
int minCon = Integer.valueOf(element.getAttribute("minCon")); /**
* 读取负载均衡配置
* 1. balance="0", 不开启分离机制，所有读操作都发送到当前可用的 writeHost 上。
* 2. balance="1"，全部的 readHost 和 stand by writeHost 参不 select 的负载均衡
* 3. balance="2"，所有读操作都随机的在 writeHost、readhost 上分发。
* 4. balance="3"，所有读请求随机的分发到 wiriterHost 对应的 readhost 执行，writerHost 不负担读压力
*/
int balance = Integer.valueOf(element.getAttribute("balance")); /**
* 读取切换类型
* -1 表示不自动切换
* 1 默认值，自动切换
* 2 基于MySQL主从同步的状态决定是否切换
* 心跳询句为 show slave status
* 3 基于 MySQL galary cluster 的切换机制
*/
String switchTypeStr = element.getAttribute("switchType"); int switchType = switchTypeStr.equals("") ? -1 : Integer.valueOf(switchTypeStr); //读取从延迟界限
String slaveThresholdStr = element.getAttribute("slaveThreshold"); int slaveThreshold = slaveThresholdStr.equals("") ? -1 : Integer.valueOf(slaveThresholdStr); //如果 tempReadHostAvailable 设置大于 0 则表示写主机如果挂掉， 临时的读服务依然可用
String tempReadHostAvailableStr = element.getAttribute("tempReadHostAvailable");
boolean tempReadHostAvailable = tempReadHostAvailableStr.equals("") ? false : Integer.valueOf(tempReadHostAvailableStr) > 0; /**
* 读取 写类型
* 这里只支持 0 - 所有写操作仅配置的第一个 writeHost
*/
String writeTypStr = element.getAttribute("writeType"); int writeType = "".equals(writeTypStr) ? PhysicalDBPool.WRITE_ONLYONE_NODE : Integer.valueOf(writeTypStr);
String dbDriver = element.getAttribute("dbDriver");
String dbType = element.getAttribute("dbType");
String filters = element.getAttribute("filters");
String logTimeStr = element.getAttribute("logTime"); long logTime = "".equals(logTimeStr) ? PhysicalDBPool.LONG_TIME : Long.valueOf(logTimeStr) ; //读取心跳语句
String heartbeatSQL = element.getElementsByTagName("heartbeat").item(0).getTextContent(); //读取 初始化sql配置,用于oracle
NodeList connectionInitSqlList = element.getElementsByTagName("connectionInitSql");
String initConSQL = null; if (connectionInitSqlList.getLength() > 0) {
initConSQL = connectionInitSqlList.item(0).getTextContent();
} //读取writeHost
NodeList writeNodes = element.getElementsByTagName("writeHost");
DBHostConfig[] writeDbConfs = new DBHostConfig[writeNodes.getLength()];
Map<Integer, DBHostConfig[]> readHostsMap = new HashMap<Integer, DBHostConfig[]>(2); for (int w = 0; w < writeDbConfs.length; w++) {
Element writeNode = (Element) writeNodes.item(w);
writeDbConfs[w] = createDBHostConf(name, writeNode, dbType, dbDriver, maxCon, minCon,filters,logTime);
NodeList readNodes = writeNode.getElementsByTagName("readHost"); //读取对应的每一个readHost
if (readNodes.getLength() != 0) {
DBHostConfig[] readDbConfs = new DBHostConfig[readNodes.getLength()]; for (int r = 0; r < readDbConfs.length; r++) {
Element readNode = (Element) readNodes.item(r);
readDbConfs[r] = createDBHostConf(name, readNode, dbType, dbDriver, maxCon, minCon,filters, logTime);
}
readHostsMap.put(w, readDbConfs);
}
}
DataHostConfig hostConf = new DataHostConfig(name, dbType, dbDriver,
writeDbConfs, readHostsMap, switchType, slaveThreshold, tempReadHostAvailable);
hostConf.setMaxCon(maxCon);
hostConf.setMinCon(minCon);
hostConf.setBalance(balance);
hostConf.setWriteType(writeType);
hostConf.setHearbeatSQL(heartbeatSQL);
hostConf.setConnectionInitSql(initConSQL);
hostConf.setFilters(filters);
hostConf.setLogTime(logTime);
dataHosts.put(hostConf.getName(), hostConf);
}
}先读取每个DataHost的通用配置，之后读取每个DataHost对应的writeHost以及每个writeHost对应的readHost。配置好后，保存在：
private final Map<String, DataHostConfig> dataHosts;
之后读取载入DataHost： XMLSchemaLoader.java:
private void loadDataNodes(Element root) { //读取DataNode分支
NodeList list = root.getElementsByTagName("dataNode"); for (int i = 0, n = list.getLength(); i < n; i++) {
Element element = (Element) list.item(i);
String dnNamePre = element.getAttribute("name");
String databaseStr = element.getAttribute("database");
String host = element.getAttribute("dataHost"); //字符串不为空
if (empty(dnNamePre) || empty(databaseStr) || empty(host)) { throw new ConfigException("dataNode " + dnNamePre + " define error ,attribute can't be empty");
} //dnNames（name）,databases（database）,hostStrings（dataHost）都可以配置多个，以',', '$', '-'区分，但是需要保证database的个数*dataHost的个数=name的个数
//多个dataHost与多个database如果写在一个标签，则每个dataHost拥有所有database
//例如：<dataNode name="dn1$0-75" dataHost="localhost$1-10" database="db$0-759" />
//则为：localhost1拥有dn1$0-75,localhost2也拥有dn1$0-75（对应db$76-151）
String[] dnNames = io.mycat.util.SplitUtil.split(dnNamePre, ',', '$', '-');
String[] databases = io.mycat.util.SplitUtil.split(databaseStr, ',', '$', '-');
String[] hostStrings = io.mycat.util.SplitUtil.split(host, ',', '$', '-'); if (dnNames.length > 1 && dnNames.length != databases.length * hostStrings.length) { throw new ConfigException("dataNode " + dnNamePre
+ " define error ,dnNames.length must be=databases.length*hostStrings.length");
} if (dnNames.length > 1) {
List<String[]> mhdList = mergerHostDatabase(hostStrings, databases); for (int k = 0; k < dnNames.length; k++) {
String[] hd = mhdList.get(k);
String dnName = dnNames[k];
String databaseName = hd[1];
String hostName = hd[0];
createDataNode(dnName, databaseName, hostName);
}
} else {
createDataNode(dnNamePre, databaseStr, host);
}
}
}private void createDataNode(String dnName, String database, String host) {
DataNodeConfig conf = new DataNodeConfig(dnName, database, host);
if (dataNodes.containsKey(conf.getName())) { throw new ConfigException("dataNode " + conf.getName() + " duplicated!");
} if (!dataHosts.containsKey(host)) { throw new ConfigException("dataNode " + dnName + " reference dataHost:" + host + " not exists!");
}
dataNodes.put(conf.getName(), conf);
}生成的是DataNode类，放入：
private final Map<String, DataNodeConfig> dataNodes;
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