This is the 20th day of my participation in the August Text Challenge.More challenges in August

Sequence diagram

sequenceDiagram
participant A as XMLMapperBuilder
participant B as XMLStatementBuilder
participant C as XMLLanguageDriver
participant D as MapperBuilderAssistant

A ->> A : buildStatementFromContext
A ->> B : parseStatementNode
B ->> C : createSqlSource
C -->> B : SqlSource
B ->> D : addMappedStatement

The detailed steps

XMLMapperBuilder#configurationElement

/** * Parse the mapping file's lower node *@paramContext mapping file root */
private void configurationElement(XNode context) {
    try {
        // Reads the namespace of the current mapping file
        String namespace = context.getStringAttribute("namespace");
        if (namespace == null || namespace.equals("")) {
            throw new BuilderException("Mapper's namespace cannot be empty");
        }
        builderAssistant.setCurrentNamespace(namespace);
        // Resolve other configuration nodes in the mapping file
        // Parse the cache label
        cacheRefElement(context.evalNode("cache-ref"));
        cacheElement(context.evalNode("cache"));
        // Parse the parameter mapping
        parameterMapElement(context.evalNodes("/mapper/parameterMap"));
        // Parse the result set mapping
        resultMapElements(context.evalNodes("/mapper/resultMap"));
        // Parse SQL tags
        sqlElement(context.evalNodes("/mapper/sql"));
        // Process individual database operation statements
        buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
    } catch (Exception e) {
        throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: "+ e, e); }}Copy the code

XMLMapperBuilder#buildStatementFromContext

private void buildStatementFromContext(List<XNode> list) {
    // The global databaseId attribute is not empty
    if(configuration.getDatabaseId() ! =null) {
        buildStatementFromContext(list, configuration.getDatabaseId());
    }
    buildStatementFromContext(list, null);
}

private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
    for (XNode context : list) {
        // Create a parse object
        final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
        try {
            / / parsing
            statementParser.parseStatementNode();
        } catch (IncompleteElementException e) {
            // Put the unprocessed items into the container and retry laterconfiguration.addIncompleteStatement(statementParser); }}}Copy the code

XMLStatementBuilder#parseStatementNode

/** * parse select, INSERT, update, delete nodes */
public void parseStatementNode(a) {
    // Read the current node ID and databaseId
    String id = context.getStringAttribute("id");
    String databaseId = context.getStringAttribute("databaseId");

    // Verify that id matches databaseId. MyBatis allows multiple database configurations, so some statements only apply to specific databases
    if(! databaseIdMatchesCurrent(id, databaseId,this.requiredDatabaseId)) {
        return;
    }

    // Read the node name
    String nodeName = context.getNode().getNodeName();
    // Read and determine the statement type
    SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
    boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
    boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
    boolean useCache = context.getBooleanAttribute("useCache", isSelect);
    boolean resultOrdered = context.getBooleanAttribute("resultOrdered".false);

    // Process the Include node in the statement
    // Include Fragments before parsing
    XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
    includeParser.applyIncludes(context.getNode());

    // Parameter type
    String parameterType = context.getStringAttribute("parameterType");
    /** * 1. Find the corresponding class in the alias mapper according to the attribute value * 2. If not in the alias mapper, the Class object */ corresponding to the Class name is createdClass<? > parameterTypeClass = resolveClass(parameterType);// Statement type, default is XMLLanguageDriver (created in the Configuration default constructor)
    String lang = context.getStringAttribute("lang");
    LanguageDriver langDriver = getLanguageDriver(lang);

    / / processing SelectKey node where KeyGenerator will be added to the Configuration. The keyGenerators
    // Parse selectKey after includes and remove them.
    processSelectKeyNodes(id, parameterTypeClass, langDriver);

    // At this point, the 
      
        and 
       
         nodes have been parsed and deleted to begin SQL parsing
       
      
    // Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
    KeyGenerator keyGenerator;
    String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX;
    keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true);
    // Determine if there is a resolved KeyGenerator
    if (configuration.hasKeyGenerator(keyStatementId)) {
        keyGenerator = configuration.getKeyGenerator(keyStatementId);
    } else {
        // Automatic key generation is used globally or whenever automatic key generation is enabled in this statement
        keyGenerator = context.getBooleanAttribute("useGeneratedKeys",
                configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType))
                ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
    }

    // Create the SqlSource based on the LanguageDriver obtained
    SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);
    // Read the configuration properties
    StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
    Integer fetchSize = context.getIntAttribute("fetchSize");
    Integer timeout = context.getIntAttribute("timeout");
    String parameterMap = context.getStringAttribute("parameterMap");
    String resultType = context.getStringAttribute("resultType"); Class<? > resultTypeClass = resolveClass(resultType); String resultMap = context.getStringAttribute("resultMap");
    String resultSetType = context.getStringAttribute("resultSetType");
    ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);
    if (resultSetTypeEnum == null) {
        resultSetTypeEnum = configuration.getDefaultResultSetType();
    }
    String keyProperty = context.getStringAttribute("keyProperty");
    String keyColumn = context.getStringAttribute("keyColumn");
    String resultSets = context.getStringAttribute("resultSets");

    // Create the MappedStatement object with the help of the MapperBuilderAssistant and write it to the Configuration
    builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
            fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
            resultSetTypeEnum, flushCache, useCache, resultOrdered,
            keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}
Copy the code

This is Mybatis parsing the select | insert | update process | delete tags.