Mybatis源码学习1-配置解析1-SqlSessionFactoryBuilder

版本说明：mybatis3.4.0

一、 入口类 SqlSessionFactoryBuilder

 public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
        SqlSessionFactory var5;
        try {
            XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
            var5 = this.build(parser.parse());
        } catch (Exception var14) {
            throw ExceptionFactory.wrapException("Error building SqlSession.", var14);
        } finally {
            ErrorContext.instance().reset();

            try {
                reader.close();
            } catch (IOException var13) {
            }

        }
        return var5;
    } 
    public SqlSessionFactory build(Configuration config) {
        return new DefaultSqlSessionFactory(config);
    }

主要工作：

将xml配置文件解析出来封装成Configuration、并且创建DefaultSqlSessionFactory工厂。

1、XMLConfigBuilder

通过名字就知道这是，xml解析成configuration的建造器:XMLConfigBuilder.parse（）解析出Configuration

创建这个XMLConfigBuilder对象、使用了XPathParser解析。mybatis所有的xml解析都是通过该解析器解析的。XPathParser把节点解析成XNode方便取出xml的属性值

除了上面的XMLConfigBuilder，还有XMLMapperBuilder、XMLStatementBuilder都是使用XPathParser的解析器。

    public XMLConfigBuilder(Reader reader, String environment, Properties props) {
        this(new XPathParser(reader, true, props, new XMLMapperEntityResolver()), environment, props);
    }

2 XPathParser

public class XPathParser {
    private Document document;
    private boolean validation;
    private EntityResolver entityResolver;
    private Properties variables;
    private XPath xpath;
    //...
    }

我们可以看到mybatis的解析使用了Document和XPath

什么是XPath？

XPath使用路径表达式在XML文档中进行导航、
XPath包含一个标准函数库、
XPath是 XSLT 中的主要元素、
XPath是一个 W3C 标准

有兴趣可以去查查XPath的文档、和说明

3、XMLConfigBuilder使用XPathParser解析出我们最终需要的Configuration

    public Configuration parse() {
        if (this.parsed) {
            throw new BuilderException("Each XMLConfigBuilder can only be used once.");
        } else {
            this.parsed = true;
            this.parseConfiguration(this.parser.evalNode("/configuration"));//使用XPathParser表达式解析出节点configuration
            return this.configuration;
        }
    }

    private void parseConfiguration(XNode root) {//继续解析根节点下面的节点，root.evalNode("")取出节点方便
        try {
            Properties settings = this.settingsAsPropertiess(root.evalNode("settings"));
            this.propertiesElement(root.evalNode("properties"));
            this.loadCustomVfs(settings);
            this.typeAliasesElement(root.evalNode("typeAliases"));
            this.pluginElement(root.evalNode("plugins"));
            this.objectFactoryElement(root.evalNode("objectFactory"));
            this.objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
            this.reflectionFactoryElement(root.evalNode("reflectionFactory"));
            this.settingsElement(settings);
            this.environmentsElement(root.evalNode("environments"));
            this.databaseIdProviderElement(root.evalNode("databaseIdProvider"));
            this.typeHandlerElement(root.evalNode("typeHandlers"));
            this.mapperElement(root.evalNode("mappers"));
        } catch (Exception var3) {
            throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + var3, var3);
        }
    }

二、我们有了解析器XPathParser，取出xml文件中的属性变得容易了，mybatis，陆续把解析出来的内容包装成各种对象，最终全部放到Configuration中

Configuration中包含的属性

  protected Environment environment;
  protected boolean safeRowBoundsEnabled;
  protected boolean safeResultHandlerEnabled;
  protected boolean mapUnderscoreToCamelCase;
  protected boolean aggressiveLazyLoading;
  protected boolean multipleResultSetsEnabled;
  protected boolean useGeneratedKeys;
  protected boolean useColumnLabel;
  protected boolean cacheEnabled;
  protected boolean callSettersOnNulls;
  protected String logPrefix;
  protected Class<? extends Log> logImpl;
  protected Class<? extends VFS> vfsImpl;
  protected LocalCacheScope localCacheScope;
  protected JdbcType jdbcTypeForNull;
  protected Set<String> lazyLoadTriggerMethods;
  protected Integer defaultStatementTimeout;
  protected Integer defaultFetchSize;
  protected ExecutorType defaultExecutorType;
  protected AutoMappingBehavior autoMappingBehavior;
  protected AutoMappingUnknownColumnBehavior autoMappingUnknownColumnBehavior;
  protected Properties variables;
  protected ReflectorFactory reflectorFactory;
  protected ObjectFactory objectFactory;
  protected ObjectWrapperFactory objectWrapperFactory;
  protected MapperRegistry mapperRegistry;
  protected boolean lazyLoadingEnabled;
  protected ProxyFactory proxyFactory;
  protected String databaseId;
  protected Class<?> configurationFactory;
  protected final InterceptorChain interceptorChain;
  protected final TypeHandlerRegistry typeHandlerRegistry;
  protected final TypeAliasRegistry typeAliasRegistry;
  protected final LanguageDriverRegistry languageRegistry;
  protected final Map<String, MappedStatement> mappedStatements;//这个是我们最关注的的、这个是我们最关注的的、这个是我们最关注的的、
  protected final Map<String, Cache> caches;
  protected final Map<String, ResultMap> resultMaps;
  protected final Map<String, ParameterMap> parameterMaps;
  protected final Map<String, KeyGenerator> keyGenerators;
  protected final Set<String> loadedResources;
  protected final Map<String, XNode> sqlFragments;
  protected final Collection<XMLStatementBuilder> incompleteStatements;
  protected final Collection<CacheRefResolver> incompleteCacheRefs;
  protected final Collection<ResultMapResolver> incompleteResultMaps;
  protected final Collection<MethodResolver> incompleteMethods;
  protected final Map<String, String> cacheRefMap;

MappedStatement

即一个sql语句对应一个MappedStatment对象、该对象储存了我们执行sql所需要的内容。

mybatis执行器，执行的参数就是MappedStatement、下面贴几个接口

public interface Executor {
   ResultHandler NO_RESULT_HANDLER = null;

   int update(MappedStatement var1, Object var2) throws SQLException;

   <E> List<E> query(MappedStatement var1, Object var2, RowBounds var3, ResultHandler var4, CacheKey var5, BoundSql var6) throws SQLException;

   <E> List<E> query(MappedStatement var1, Object var2, RowBounds var3, ResultHandler var4) throws SQLException;
//......
}

下章我们在讲mapper解析的过程、
Mybatis源码学习2-配置解析2-XMLMapperBuilder