In layman's language Mybatis series (three) --- Configuration Profile (mybatis source article)

The article, " in layman's language Mybatis series (two) --- Mybatis entry " wrote a simple Demo reflect a bit Mybatis process. This will be a brief Mybatis profile:

The last example, we go to SqlSessionFactoryBuilder create SqlSessionFactory, then we start SqlSessionFactoryBuilder start, let's take a look at the source code is how to achieve:

SqlSessionFactoryBuilder source code fragment:

public class SqlSessionFactoryBuilder {

  // Reader reads mybatis configuration file, passed in the constructor
   // In addition to Reader, there is also a corresponding inputStream as a constructor parameter
   // It also reflects the flexibility of configuration mybatis 
  public SqlSessionFactory Build (Reader Reader) {
     return Build (Reader, null , null );
  }

  public SqlSessionFactory build(Reader reader, String environment) {
    return build(reader, environment, null);
  }
  
  // mybatis profile + properties, this case may not mybatis profile configuration properties, can also be used in the form of $ {} 
  public a SqlSessionFactory Build (Reader Reader, the Properties Properties) {
     return Build (Reader, null , Properties);
  }
  
  // By XMLConfigBuilder resolve mybatis configuration, and then create a SqlSessionFactory 
  public SqlSessionFactory Build (Reader Reader, String Environment, the Properties the Properties) {
     the try {
      Parser XMLConfigBuilder = new new XMLConfigBuilder (Reader, Environment, Properties);
       // The following look at the source of this method 
      return Build (parser.parse ());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        reader.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }
  }

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

}

By source code, we can see SqlSessionFactoryBuilder to resolve our incoming mybatis profile by XMLConfigBuilder, to then take a look at the following section XMLConfigBuilder Source:

/**
 * Mybatis configuration file parsing
 */
public class XMLConfigBuilder extends BaseBuilder {
  public XMLConfigBuilder(InputStream inputStream, String environment, Properties props) {
    this(new XPathParser(inputStream, true, props, new XMLMapperEntityResolver()), environment, props);
  }

  private XMLConfigBuilder(XPathParser parser, String environment, Properties props) {
    super(new Configuration());
    ErrorContext.instance().resource("SQL Mapper Configuration");
    this.configuration.setVariables(props);
    this.parsed = false;
    this.environment = environment;
    this.parser = parser;
  }
  
  // external call this method on mybatis configuration file is parsed 
  public the Configuration the parse () {
     IF (of Parsed) {
       the throw  new new BuilderException ( "Each XMLConfigBuilder only CAN BE Used Once." );
    }
    parsed = true;
    //从根节点configuration
    parseConfiguration(parser.evalNode("/configuration"));
    return configuration;
  }

  // This method is to parse the next child node of the node configuration
   // This also can be seen, the nodes that we can be configured in the following configuration of the nodes 10 
  Private  void parseConfiguration (XNode the root) {
     the try {
      propertiesElement(root.evalNode("properties")); //issue #117 read properties first
      typeAliasesElement(root.evalNode("typeAliases"));
      pluginElement(root.evalNode("plugins"));
      objectFactoryElement(root.evalNode("objectFactory"));
      objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
      settingsElement(root.evalNode("settings"));
      environmentsElement(root.evalNode("environments")); // read it after objectFactory and objectWrapperFactory issue #631
      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);
    }
  }
}

Through the above source code, we can see that in mybatis configuration file:

1. configuration node as a root.

2. Under the configuration node, we can configure the 10 sub-node, respectively: properties, typeAliases, plugins, objectFactory, objectWrapperFactory, settings, environments, databaseIdProvider, typeHandlers, mappers.

 

This article only describes the contents on the first, the next article will turn 10 this analysis to resolve the source node of the more important a few nodes to see when parsing these nodes, in the end done.

/** * mybatis 配置文件解析 */public class XMLConfigBuilder extends BaseBuilder {  public XMLConfigBuilder(InputStream inputStream, String environment, Properties props) {    this(new XPathParser(inputStream, true, props, new XMLMapperEntityResolver()), environment, props);  }
  private XMLConfigBuilder(XPathParser parser, String environment, Properties props) {    super(new Configuration());    ErrorContext.instance().resource("SQL Mapper Configuration");    this.configuration.setVariables(props);    this.parsed = false;    this.environment = environment;    this.parser = parser;  }    //外部调用此方法对mybatis配置文件进行解析  public Configuration parse() {    if (parsed) {      throw new BuilderException("Each XMLConfigBuilder can only be used once.");    }    parsed = true;    //从根节点configuration    parseConfiguration(parser.evalNode("/configuration"));    return configuration;  }
  // This method is to parse the next child node of the node configuration // This also can be seen, the nodes that we can be configured in the following configuration of the nodes 10 private void parseConfiguration (XNode root) {try {propertiesElement (root.evalNode ( "properties")); // issue # 117 read properties first typeAliasesElement (root.evalNode ( "typeAliases")); pluginElement (root.evalNode ( "plugins")); objectFactoryElement (root.evalNode ( "objectFactory")); objectWrapperFactoryElement (root.evalNode ( "objectWrapperFactory")); settingsElement (root.evalNode ( "settings")); environmentsElement (root.evalNode ( "environments")); // read it after objectFactory and objectWrapperFactory issue # 631 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);    }  }}