一、SqlSessionFactory 对象初始化
//加载全局配置文件
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
//1.获取SqlSessionFactory对象
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
1.调用SqlSessionFactoryBuilder的build(inputStream);方法,方法如下:
public SqlSessionFactory build(InputStream inputStream) {
return build(inputStream, null, null);
}
实际上调用如下方法;
public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
try {
//XMLConfigBuilder是对mybatis的配置文件进行解析的类
XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
//1.调用当前类的parse() 方法,返回configuration。2.调用build方法,返回SqlSessionFactory
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.
}
}
}
- 首先传入全局配置文件的输入流,创建了XMLConfigBuilder对象。然后调用XMLConfigBuilder 的parse()方法。代码如下:
public Configuration parse() {
//判断Configuration是否解析过,Configuration是全局变量,只需要解析创建一次即可
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
//调用下面的方法,parser.evalNode("/configuration")解析XML配置的configuration节点的内容,得到XNode对象
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}
parser.evalNode(“/configuration”)是调用了XPathParser类的evalNode方法返回的是XNode对象。XNode对象保存了解析后的对应节点下的所有信息。
- 然后parseConfiguration(parser.evalNode("/configuration")); 方法,代码如下:
//根据root中存储的是configuration节点的内容
private void parseConfiguration(XNode root) {
try {
//设置settings配置
Properties settings = settingsAsPropertiess(root.evalNode("settings"));
//设置properties配置
propertiesElement(root.evalNode("properties"));
loadCustomVfs(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"));
//设置mappers配置
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
可以看出parse的作用是解析mybatis-config.xml的configuration节点的内容,然后挨个赋值给configuration对象的属性;
- settingsElement(settings); 方法如下:将全局配置文件中所有结点的配置信息都设置到了configuration对象中
private void settingsElement(Properties props) throws Exception {
configuration.setAutoMappingBehavior(AutoMappingBehavior.valueOf(props.getProperty("autoMappingBehavior", "PARTIAL")));
configuration.setAutoMappingUnknownColumnBehavior(AutoMappingUnknownColumnBehavior.valueOf(props.getProperty("autoMappingUnknownColumnBehavior", "NONE")));
configuration.setCacheEnabled(booleanValueOf(props.getProperty("cacheEnabled"), true));
- mapperElement(root.evalNode("mappers")); 方法,则是将是对SQL映射文件进行了解析。解析后将信息设置到了configuration对象中
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();
解析mapper映射文件代码如下:
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. Cause: " + e, e);
}
}
到这里 return build(parser.parse()); 就要返回了,build方法如下:
public SqlSessionFactory build(Configuration config) {
return new DefaultSqlSessionFactory(config);
}
返回的SqlSessionFactory 对象中封装了所有的配置信息。Configuration封装了所有配置文件的详细信息。