剖析Mybatis Plus实现动态SQL语句的机理
java1234
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·
2021-09-03 20:37
入口类：MybatisSqlSessionFactoryBuilder
public class MybatisSqlSessionFactoryBuilder extends SqlSessionFactoryBuilder {
public SqlSessionFactory build(Configuration configuration) {
// ... 省略若干行
if (globalConfig.isEnableSqlRunner()) {
new SqlRunnerInjector().inject(configuration);
}
// ... 省略若干行
return sqlSessionFactory;
}
}
扩展继承自Mybatis的MybatisConfiguration类: MP动态脚本构建，注册，及其它逻辑判断。 SqlRunnerInjector: MP默认插入一些动态方法的xml 脚本方法。
MybatisConfiguration类
MybatisConfiguration中很多方法是使用MybatisMapperRegistry进行重写实现
public class MybatisConfiguration extends Configuration {
/**
* Mapper 注册
*/
protected final MybatisMapperRegistry mybatisMapperRegistry = new MybatisMapperRegistry(this);
// ....
/**
* 初始化调用
*/
public MybatisConfiguration() {
super();
this.mapUnderscoreToCamelCase = true;
languageRegistry.setDefaultDriverClass(MybatisXMLLanguageDriver.class);
}
/**
* MybatisPlus 加载 SQL 顺序：
* <p> 1、加载 XML中的 SQL </p>
* <p> 2、加载 SqlProvider 中的 SQL </p>
* <p> 3、XmlSql 与 SqlProvider不能包含相同的 SQL </p>
* <p>调整后的 SQL优先级：XmlSql > sqlProvider > CurdSql </p>
*/
@Override
public void addMappedStatement(MappedStatement ms) {
// ...
}
// ... 省略若干行
/**
* 使用自己的 MybatisMapperRegistry
*/
@Override
public <T> void addMapper(Class<T> type) {
mybatisMapperRegistry.addMapper(type);
}
// .... 省略若干行
}
在MybatisMapperRegistry中，MP将mybatis的MapperAnnotationBuilder替换为MP自己的MybatisMapperAnnotationBuilder
public class MybatisMapperRegistry extends MapperRegistry {
@Override
public <T> void addMapper(Class<T> type) {
// ... 省略若干行
MybatisMapperAnnotationBuilder parser = new MybatisMapperAnnotationBuilder(config, type);
parser.parse();
// ... 省略若干行
}
}
MybatisMapperAnnotationBuilder动态构造
public class MybatisMapperAnnotationBuilder extends MapperAnnotationBuilder {
@Override
public void parse() {
//... 省略若干行
for (Method method : type.getMethods()) {
/** for循环代码, MP判断method方法是否是@Select @Insert等mybatis注解方法**/
parseStatement(method);
InterceptorIgnoreHelper.initSqlParserInfoCache(cache, mapperName, method);
SqlParserHelper.initSqlParserInfoCache(mapperName, method);
}
/** 这2行代码, MP注入默认的方法列表**/
if (GlobalConfigUtils.isSupperMapperChildren(configuration, type)) {
GlobalConfigUtils.getSqlInjector(configuration).inspectInject(assistant, type);
}
//... 省略若干行
}
@Override
public void inspectInject(MapperBuilderAssistant builderAssistant, Class<?> mapperClass) {
Class<?> modelClass = extractModelClass(mapperClass);
//... 省略若干行
List<AbstractMethod> methodList = this.getMethodList(mapperClass);
TableInfo tableInfo = TableInfoHelper.initTableInfo(builderAssistant, modelClass);
// 循环注入自定义方法
methodList.forEach(m -> m.inject(builderAssistant, mapperClass, modelClass, tableInfo));
mapperRegistryCache.add(className);
}
}
public class DefaultSqlInjector extends AbstractSqlInjector {
@Override
public List<AbstractMethod> getMethodList(Class<?> mapperClass) {
return Stream.of(
new Insert(),
//... 省略若干行
new SelectPage()
).collect(toList());
}
}
具体的AbstractMethod实例类，构造具体的方法SQL语句
/**
* 根据ID 查询一条数据
*/
public class SelectById extends AbstractMethod {
@Override
public MappedStatement injectMappedStatement(Class<?> mapperClass, Class<?> modelClass, TableInfo tableInfo) {
/** 定义 mybatis xml method id, 对应 <id="xyz"> **/
SqlMethod sqlMethod = SqlMethod.SELECT_BY_ID;
/** 构造id对应的具体xml片段 **/
SqlSource sqlSource = new RawSqlSource(configuration, String.format(sqlMethod.getSql(),
sqlSelectColumns(tableInfo, false),
tableInfo.getTableName(), tableInfo.getKeyColumn(), tableInfo.getKeyProperty(),
tableInfo.getLogicDeleteSql(true, true)), Object.class);
/** 将xml method方法添加到mybatis的MappedStatement中 **/
return this.addSelectMappedStatementForTable(mapperClass, getMethod(sqlMethod), sqlSource, tableInfo);
}
}
总结一下
public class YourSqlSessionFactoryBean extends SqlSessionFactoryBean implements ApplicationContextAware {
private Resource[] mapperLocations;
@Override
public void setMapperLocations(Resource... mapperLocations) {
super.setMapperLocations(mapperLocations);
/** 暂存使用mybatis原生定义的mapper xml文件路径**/
this.mapperLocations = mapperLocations;
}
/**
* {@inheritDoc}
*/
@Override
public void afterPropertiesSet() throws Exception {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
/** 只需要通过将自定义的方法构造成xml resource和原生定义的Resource一起注入到mybatis中即可, 这样就可以实现MP的自定义动态SQL和原生SQL的共生关系**/
this.setMapperLocations(InjectMapper.getMapperResource(this.dbType, beanFactory, this.mapperLocations));
super.afterPropertiesSet();
}
}
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