MyCat - 源代码篇（12）

数据库路由中间件MyCat - 源代码篇（12）

4.配置模块

4.2 schema.xml

接上一篇，接下来载入每个schema的配置（也就是每个MyCat中虚拟化的数据库的配置）：
XMLSchemaLoader.java

private void loadSchemas(Element root) {        NodeList list = root.getElementsByTagName("schema");    for (int i = 0, n = list.getLength(); i < n; i++) {        Element schemaElement = (Element) list.item(i);        //读取各个属性        String name = schemaElement.getAttribute("name");        String dataNode = schemaElement.getAttribute("dataNode");        String checkSQLSchemaStr = schemaElement.getAttribute("checkSQLschema");        String sqlMaxLimitStr = schemaElement.getAttribute("sqlMaxLimit");        int sqlMaxLimit = -1;        //读取sql返回结果集限制        if (sqlMaxLimitStr != null && !sqlMaxLimitStr.isEmpty()) {            sqlMaxLimit = Integer.valueOf(sqlMaxLimitStr);        }        // check dataNode already exists or not,看schema标签中是否有datanode        String defaultDbType = null;        //校验检查并添加dataNode        if (dataNode != null && !dataNode.isEmpty()) {            List<String> dataNodeLst = new ArrayList<String>(1);            dataNodeLst.add(dataNode);            checkDataNodeExists(dataNodeLst);            String dataHost = dataNodes.get(dataNode).getDataHost();            defaultDbType = dataHosts.get(dataHost).getDbType();        } else {            dataNode = null;        }        //加载schema下所有tables        Map<String, TableConfig> tables = loadTables(schemaElement);        //判断schema是否重复        if (schemas.containsKey(name)) {            throw new ConfigException("schema " + name + " duplicated!");        }        // 设置了table的不需要设置dataNode属性，没有设置table的必须设置dataNode属性        if (dataNode == null && tables.size() == 0) {            throw new ConfigException(                    "schema " + name + " didn't config tables,so you must set dataNode property!");        }        SchemaConfig schemaConfig = new SchemaConfig(name, dataNode,                tables, sqlMaxLimit, "true".equalsIgnoreCase(checkSQLSchemaStr));        //设定DB类型，这对之后的sql语句路由解析有帮助        if (defaultDbType != null) {            schemaConfig.setDefaultDataNodeDbType(defaultDbType);            if (!"mysql".equalsIgnoreCase(defaultDbType)) {                schemaConfig.setNeedSupportMultiDBType(true);            }        }        // 判断是否有不是mysql的数据库类型，方便解析判断是否启用多数据库分页语法解析        for (String tableName : tables.keySet()) {            TableConfig tableConfig = tables.get(tableName);            if (isHasMultiDbType(tableConfig)) {                schemaConfig.setNeedSupportMultiDBType(true);                break;            }        }        //记录每种dataNode的DB类型        Map<String, String> dataNodeDbTypeMap = new HashMap<>();        for (String dataNodeName : dataNodes.keySet()) {            DataNodeConfig dataNodeConfig = dataNodes.get(dataNodeName);            String dataHost = dataNodeConfig.getDataHost();            DataHostConfig dataHostConfig = dataHosts.get(dataHost);            if (dataHostConfig != null) {                String dbType = dataHostConfig.getDbType();                dataNodeDbTypeMap.put(dataNodeName, dbType);            }        }        schemaConfig.setDataNodeDbTypeMap(dataNodeDbTypeMap);        schemas.put(name, schemaConfig);    }}

首先读取schema每个配置属性项，并作有效性判断。比如默认的dataNode是否存在。只要验证之前读取的dataNode里面有没有就可以

private void checkDataNodeExists(Collection<String> nodes) {    if (nodes == null || nodes.size() < 1) {        return;    }    for (String node : nodes) {        if (!dataNodes.containsKey(node)) {            throw new ConfigException("dataNode '" + node + "' is not found!");        }    }}

之后载入所有的table和childTable：

private Map<String, TableConfig> loadTables(Element node) {    // Map<String, TableConfig> tables = new HashMap<String, TableConfig>();    // 支持表名中包含引号[`] BEN GONG    Map<String, TableConfig> tables = new TableConfigMap();    NodeList nodeList = node.getElementsByTagName("table");    for (int i = 0; i < nodeList.getLength(); i++) {        Element tableElement = (Element) nodeList.item(i);        String tableNameElement = tableElement.getAttribute("name").toUpperCase();        //TODO:路由, 增加对动态日期表的支持        String tableNameSuffixElement = tableElement.getAttribute("nameSuffix").toUpperCase();        if ( !"".equals( tableNameSuffixElement ) ) {                           if( tableNameElement.split(",").length > 1 ) {                throw new ConfigException("nameSuffix " + tableNameSuffixElement + ", require name parameter cannot multiple breaks!");            }            //前缀用来标明日期格式            tableNameElement = doTableNameSuffix(tableNameElement, tableNameSuffixElement);        }        //记录主键，用于之后路由分析，以及启用自增长主键        String[] tableNames = tableNameElement.split(",");        String primaryKey = tableElement.hasAttribute("primaryKey") ? tableElement.getAttribute("primaryKey").toUpperCase() : null;        //记录是否主键自增，默认不是，（启用全局sequence handler）        boolean autoIncrement = false;        if (tableElement.hasAttribute("autoIncrement")) {            autoIncrement = Boolean.parseBoolean(tableElement.getAttribute("autoIncrement"));        }        //记录是否需要加返回结果集限制，默认需要加        boolean needAddLimit = true;        if (tableElement.hasAttribute("needAddLimit")) {            needAddLimit = Boolean.parseBoolean(tableElement.getAttribute("needAddLimit"));        }        //记录type，是否为global        String tableTypeStr = tableElement.hasAttribute("type") ? tableElement.getAttribute("type") : null;        int tableType = TableConfig.TYPE_GLOBAL_DEFAULT;        if ("global".equalsIgnoreCase(tableTypeStr)) {            tableType = TableConfig.TYPE_GLOBAL_TABLE;        }        //记录dataNode，就是分布在哪些dataNode上        String dataNode = tableElement.getAttribute("dataNode");        TableRuleConfig tableRule = null;        if (tableElement.hasAttribute("rule")) {            String ruleName = tableElement.getAttribute("rule");            tableRule = tableRules.get(ruleName);            if (tableRule == null) {                throw new ConfigException("rule " + ruleName + " is not found!");            }        }        boolean ruleRequired = false;        //记录是否绑定有分片规则        if (tableElement.hasAttribute("ruleRequired")) {            ruleRequired = Boolean.parseBoolean(tableElement.getAttribute("ruleRequired"));        }        if (tableNames == null) {            throw new ConfigException("table name is not found!");        }        //distribute函数，重新编排dataNode        String distPrex = "distribute(";        boolean distTableDns = dataNode.startsWith(distPrex);        if (distTableDns) {            dataNode = dataNode.substring(distPrex.length(), dataNode.length() - 1);        }        //分表功能        String subTables = tableElement.getAttribute("subTables");        for (int j = 0; j < tableNames.length; j++) {            String tableName = tableNames[j];            TableConfig table = new TableConfig(tableName, primaryKey,                    autoIncrement, needAddLimit, tableType, dataNode,                    getDbType(dataNode),                    (tableRule != null) ? tableRule.getRule() : null,                    ruleRequired, null, false, null, null,subTables);            checkDataNodeExists(table.getDataNodes());            if (distTableDns) {                distributeDataNodes(table.getDataNodes());            }            //检查去重            if (tables.containsKey(table.getName())) {                throw new ConfigException("table " + tableName + " duplicated!");            }            //放入map            tables.put(table.getName(), table);        }        //只有tableName配置的是单个表（没有逗号）的时候才能有子表        if (tableNames.length == 1) {            TableConfig table = tables.get(tableNames[0]);            // process child tables            processChildTables(tables, table, dataNode, tableElement);        }    }    return tables;}

对于子表，有递归读取配置：

private void processChildTables(Map<String, TableConfig> tables,            TableConfig parentTable, String dataNodes, Element tableNode) {        // parse child tables        NodeList childNodeList = tableNode.getChildNodes();        for (int j = 0; j < childNodeList.getLength(); j++) {            Node theNode = childNodeList.item(j);            if (!theNode.getNodeName().equals("childTable")) {                continue;            }            Element childTbElement = (Element) theNode;            //读取子表信息            String cdTbName = childTbElement.getAttribute("name").toUpperCase();            String primaryKey = childTbElement.hasAttribute("primaryKey") ? childTbElement.getAttribute("primaryKey").toUpperCase() : null;            boolean autoIncrement = false;            if (childTbElement.hasAttribute("autoIncrement")) {                autoIncrement = Boolean.parseBoolean(childTbElement.getAttribute("autoIncrement"));            }            boolean needAddLimit = true;            if (childTbElement.hasAttribute("needAddLimit")) {                needAddLimit = Boolean.parseBoolean(childTbElement.getAttribute("needAddLimit"));            }            String subTables = childTbElement.getAttribute("subTables");            //子表join键，和对应的parent的键，父子表通过这个关联            String joinKey = childTbElement.getAttribute("joinKey").toUpperCase();            String parentKey = childTbElement.getAttribute("parentKey").toUpperCase();            TableConfig table = new TableConfig(cdTbName, primaryKey,                    autoIncrement, needAddLimit,                    TableConfig.TYPE_GLOBAL_DEFAULT, dataNodes,                    getDbType(dataNodes), null, false, parentTable, true,                    joinKey, parentKey, subTables);            if (tables.containsKey(table.getName())) {                throw new ConfigException("table " + table.getName() + " duplicated!");            }            tables.put(table.getName(), table);            //对于子表的子表，递归处理            processChildTables(tables, table, dataNodes, childTbElement);        }    }

对于表的dataNode对应关系，有个特殊配置即类似dataNode=”distributed(dn$1-10)”，这个含义是：

/**     * distribute datanodes in multi hosts,means ,dn1 (host1),dn100     * (host2),dn300(host3),dn2(host1),dn101(host2),dn301(host3)...etc     *  将每个host上的datanode按照host重新排列。比如上面的例子host1拥有dn1,dn2，host2拥有dn100，dn101，host3拥有dn300，dn301,     * 按照host重新排列： 0->dn1 (host1),1->dn100(host2),2->dn300(host3),3->dn2(host1),4->dn101(host2),5->dn301(host3)     *     * @param theDataNodes     */    private void distributeDataNodes(ArrayList<String> theDataNodes) {        Map<String, ArrayList<String>> newDataNodeMap = new HashMap<String, ArrayList<String>>(dataHosts.size());        for (String dn : theDataNodes) {            DataNodeConfig dnConf = dataNodes.get(dn);            String host = dnConf.getDataHost();            ArrayList<String> hostDns = newDataNodeMap.get(host);            hostDns = (hostDns == null) ? new ArrayList<String>() : hostDns;            hostDns.add(dn);            newDataNodeMap.put(host, hostDns);        }        ArrayList<String> result = new ArrayList<String>(theDataNodes.size());        boolean hasData = true;        while (hasData) {            hasData = false;            for (ArrayList<String> dns : newDataNodeMap.values()) {                if (!dns.isEmpty()) {                    result.add(dns.remove(0));                    hasData = true;                }            }        }        theDataNodes.clear();        theDataNodes.addAll(result);    }

读取完所有表之后，记录好DB类型，这对之后的sql语句路由解析有帮助。将所有schema的配置保存在：

private final Map<String, SchemaConfig> schemas;

4.3 server.xml

之后会读取载入server配置。
XMLConfigLoader.java:

public XMLConfigLoader(SchemaLoader schemaLoader) {    XMLServerLoader serverLoader = new XMLServerLoader();    this.system = serverLoader.getSystem();    this.users = serverLoader.getUsers();    this.quarantine = serverLoader.getQuarantine();    this.cluster = serverLoader.getCluster();    this.dataHosts = schemaLoader.getDataHosts();    this.dataNodes = schemaLoader.getDataNodes();    this.schemas = schemaLoader.getSchemas();    schemaLoader = null;}

XMLServerLoader.java

public XMLServerLoader() {    this.system = new SystemConfig();    this.users = new HashMap<String, UserConfig>();    this.quarantine = new QuarantineConfig();    this.load();}private void load() {    //读取server.xml配置    InputStream dtd = null;    InputStream xml = null;    try {        dtd = XMLServerLoader.class.getResourceAsStream("/server.dtd");        xml = XMLServerLoader.class.getResourceAsStream("/server.xml");        Element root = ConfigUtil.getDocument(dtd, xml).getDocumentElement();        //加载System标签        loadSystem(root);        //加载User标签        loadUsers(root);        //加载集群配置        this.cluster = new ClusterConfig(root, system.getServerPort());        //加载权限和黑白名单        loadQuarantine(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) {            }        }    }}

首先加载System标签