</configuration>
<mappers>
<!-- 注册userMapper.xml文件，
userMapper.xml位于me.gacl.mapping这个包下，所以resource写成me/gacl/mapping/userMapper.xml-->
<mapper resource="sql.xml"/>
<mapper class="cn.com.ibatisdemo.ibatisdemo.UserMapper"/>
<!-- 注册UserMapper映射接口
<mapper class="me.gacl.mapping.UserMapperI"/>-->
</mappers>
</configuration>
XMLConfigBuilder类主要方法说明
方法一：
public Configuration parse() {
if (parsed) {
throw new BuilderException("Each MapperConfigParser can only be used once.");
}
parsed = true;
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}
方法二：
private void parseConfiguration(XNode root) {
try {
typeAliasesElement(root.evalNode("typeAliases"));
pluginElement(root.evalNode("plugins"));
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
propertiesElement(root.evalNode("properties"));
settingsElement(root.evalNode("settings"));
environmentsElement(root.evalNode("environments"));
typeHandlerElement(root.evalNode("typeHandlers"));
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
方法三：
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
InputStream inputStream;
if (resource != null && url == null) {
ErrorContext.instance().resource(resource);
inputStream = Resources.getResourceAsStream(resource);
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
mapperParser.parse();
} else if (url != null && resource == null) {
ErrorContext.instance().resource(url);
inputStream = Resources.getUrlAsStream(url);
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
mapperParser.parse();
} else {
throw new BuilderException("A mapper element may only specify a url or resource, but not both.");
}
}
}
}
说明：此版本mybatis-3.0.4有点古老，新版本是resource/url/classes三者必有其一或者使用package动态扫描，下面这个方法是mybatis-3.4.2的方法
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.");
}
}
}
}
}
总结如下：
<mappers>
<!-- 通过package元素将会把指定包下面的所有Mapper接口进行注册 -->
<package name="com.tiantian.mybatis.mapperinterface"/>
<!-- 通过mapper元素的resource属性可以指定一个相对于类路径的Mapper.xml文件 -->
<mapper resource="com/tiantian/mybatis/mapper/UserMapper.xml"/>
<!-- 通过mapper元素的url属性可以指定一个通过URL请求道的Mapper.xml文件 -->
<mapper url="file:///E:/UserMapper.xml"/>
<!-- 通过mapper元素的class属性可以指定一个Mapper接口进行注册 -->
<mapper class="com.tiantian.mybatis.mapperinterface.UserMapper"/>
</mappers>
当使用mapper元素进行Mapper定义的时候需要注意：mapper的三个属性resource、url和class对于每个mapper元素只能指定一个，要么指定resource属性，要么指定url属性，要么指定class属性，不能都指定，也不能都不指定。
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