MyBatis杂记(1)

一、入口

package org.apache.ibatis.session;

public class SqlSessionFactoryBuilder {

    public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
        try {
            XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
            return build(parser.parse());
        } catch (Exception e) {
            throw ExceptionFactory.wrapException("Error building SqlSession.", e);
        } finally {
            ErrorContext.instance().reset();
            try {
                inputStream.close();
            } catch (IOException e) {
                // Intentionally ignore. Prefer previous error.
            }
        }
    }


    public SqlSessionFactory build(Configuration config) {
        return new DefaultSqlSessionFactory(config);
    }
}

org.apache.ibatis.builder.xml.XMLConfigBuilder 加载 mybatis(mybatis-config.xml)配置信息,创建一个org.apache.ibatis.session.Configuration。

package org.apache.ibatis.builder.xml;

public class XMLConfigBuilder extends BaseBuilder {

    public Configuration parse() {
        if (parsed) {
            throw new BuilderException("Each XMLConfigBuilder can only be used once.");
        }
        parsed = true;
        parseConfiguration(parser.evalNode("/configuration"));
        return configuration;
    }

    private void parseConfiguration(XNode root) {
        try {
            //issue #117 read properties first
            propertiesElement(root.evalNode("properties"));
            Properties settings = settingsAsProperties(root.evalNode("settings"));
            loadCustomVfs(settings);
            loadCustomLogImpl(settings);
            typeAliasesElement(root.evalNode("typeAliases"));
            pluginElement(root.evalNode("plugins"));
            objectFactoryElement(root.evalNode("objectFactory"));
            objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
            reflectorFactoryElement(root.evalNode("reflectorFactory"));
            settingsElement(settings);
            // read it after objectFactory and objectWrapperFactory issue #631
            environmentsElement(root.evalNode("environments"));
            databaseIdProviderElement(root.evalNode("databaseIdProvider"));
            typeHandlerElement(root.evalNode("typeHandlers"));
            mapperElement(root.evalNode("mappers"));
        } catch (Exception e) {
            throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
        }
    }

    private void mapperElement(XNode parent) throws Exception {
        if (parent != null) {
            for (XNode child : parent.getChildren()) {
                if ("package".equals(child.getName())) {
                    String mapperPackage = child.getStringAttribute("name");
                    configuration.addMappers(mapperPackage);
                } else {
                    String resource = child.getStringAttribute("resource");
                    String url = child.getStringAttribute("url");
                    String mapperClass = child.getStringAttribute("class");
                    if (resource != null && url == null && mapperClass == null) {
                        ErrorContext.instance().resource(resource);
                        InputStream inputStream = Resources.getResourceAsStream(resource);
                        XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
                        mapperParser.parse();
                    } else if (resource == null && url != null && mapperClass == null) {
                        ErrorContext.instance().resource(url);
                        InputStream inputStream = Resources.getUrlAsStream(url);
                        XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
                        mapperParser.parse();
                    } else if (resource == null && url == null && mapperClass != null) {
                        Class<?> mapperInterface = Resources.classForName(mapperClass);
                        configuration.addMapper(mapperInterface);
                    } else {
                        throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
                    }
                }
            }
        }
    }
}

org.apache.ibatis.builder.xml.XMLConfigBuilder中mapperElement解析mappers。

package org.apache.ibatis.builder.xml;

public class XMLMapperBuilder extends BaseBuilder {

    public void parse() {
        if (!configuration.isResourceLoaded(resource)) {
            configurationElement(parser.evalNode("/mapper"));
            configuration.addLoadedResource(resource);
            bindMapperForNamespace();
        }

        parsePendingResultMaps();
        parsePendingCacheRefs();
        parsePendingStatements();
    }


    private void configurationElement(XNode context) {
        try {
            String namespace = context.getStringAttribute("namespace");
            if (namespace == null || namespace.equals("")) {
                throw new BuilderException("Mapper's namespace cannot be empty");
            }
            builderAssistant.setCurrentNamespace(namespace);
            cacheRefElement(context.evalNode("cache-ref"));
            cacheElement(context.evalNode("cache"));
            parameterMapElement(context.evalNodes("/mapper/parameterMap"));
            resultMapElements(context.evalNodes("/mapper/resultMap"));
            sqlElement(context.evalNodes("/mapper/sql"));
            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);
        }
    }

    private void buildStatementFromContext(List<XNode> list) {
        if (configuration.getDatabaseId() != null) {
            buildStatementFromContext(list, configuration.getDatabaseId());
        }
        buildStatementFromContext(list, null);
    }

    private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
        for (XNode context : list) {
            final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
            try {
                statementParser.parseStatementNode();
            } catch (IncompleteElementException e) {
                configuration.addIncompleteStatement(statementParser);
            }
        }
    }
}

org.apache.ibatis.builder.xml.XMLMapperBuilder解析mapper.xml
mybatis二级缓存配置解析:
cacheRefElement(context.evalNode("cache-ref"));
cacheElement(context.evalNode("cache"));

mapper.xml中ResultMap解析：
resultMapElements(context.evalNodes("/mapper/resultMap"));

mapper.xml中<select/><insert/><update/><delete/>解析：
buildStatementFromContext(context.evalNodes("select|insert|update|delete")); 

org.apache.ibatis.builder.xml.XMLStatementBuilder解析mapper.xml中sql语句。

总结：

XMLConfigBuilder解析mybatis-config.xml读取到mybatis-config.xml中<mappers/>标签时创建XMLMapperBuilder去解析mapper.xml，读取到mapper.xml中<select/><insert/><update/><delete/>时创建XMLStatementBuilder去解析sql。