Java的MyBatis框架中Mapper映射配置的使用及原理解析

int countByExample(UserExample example); //下面是一个完整的案列UserExample example = new UserExample(); Criteria criteria = example.createCriteria(); criteria.andUsernameEqualTo("joe"); int count = userDAO.countByExample(example);

int deleteByExample(AccountExample example); //下面是一个完整的案例UserExample example = new UserExample(); Criteria criteria = example.createCriteria(); criteria.andUsernameEqualTo("joe"); userDAO.deleteByExample(example); 相当于：delete from user where username='joe'

int deleteByPrimaryKey(Integer id);userDAO.deleteByPrimaryKey(101); 

delete from user where id=101 

int insert(Account record); //下面是完整的案例User user = new User(); //user.setId(101); user.setUsername("test"); user.setPassword("123456") user.setEmail("674531003@qq.com"); userDAO.insert(user);

insert into user(ID,username,password,email) values(101,'test','123456','674531003@qq.com');

int insertSelective(Account record);

List<Account> selectByExample(AccountExample example); //下面是一个完整的案例UserExample example = new UserExample();Criteria criteria = example.createCriteria();criteria.andUsernameEqualTo("joe");criteria.andUsernameIsNull();example.setOrderByClause("username asc,email desc");List<?>list = userDAO.selectByExample(example);相当于：select * from user where username = 'joe' and username is null order by username asc,email desc //注：在iBator 生成的文件UserExample.java中包含一个static 的内部类 Criteria ，在Criteria中有很多方法，主要是定义SQL 语句where后的查询条件。

Account selectByPrimaryKey(Integer id);//相当于select * from user where id = 变量id

int updateByExampleSelective(@Param("record") Account record, @Param("example") AccountExample example); //下面是一个完整的案列UserExample example = new UserExample(); Criteria criteria = example.createCriteria(); criteria.andUsernameEqualTo("joe"); User user = new User(); user.setPassword("123"); userDAO.updateByPrimaryKeySelective(user,example); 相当于：update user set password='123' where username='joe'

int updateByExample(@Param("record") Account record, @Param("example") AccountExample example);

int updateByPrimaryKeySelective(Account record);//下面是一个完整的案例 User user = new User();user.setId(101);user.setPassword("joe");userDAO.updateByPrimaryKeySelective(user);

update user set password='joe' where id=101

int updateByPrimaryKeySelective(Account record); //下面是一个完整的案例  User user = new User();user.setId(101);user.setPassword("joe");userDAO.updateByPrimaryKeySelective(user);

int updateByPrimaryKey(Account record);//下面是一个完整的案例User user =new User(); user.setId(101); user.setUsername("joe"); user.setPassword("joe"); user.setEmail("joe@163.com"); userDAO.updateByPrimaryKey(user);

update user set username='joe',password='joe',email='joe@163.com' where id=101

int updateByPrimaryKey(Account record); //下面是一个完整的案例User user =new User(); user.setId(101); user.setUsername("joe"); user.setPassword("joe"); user.setEmail("joe@163.com"); userDAO.updateByPrimaryKey(user);

update user set username='joe',password='joe',email='joe@163.com' where id=101

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">     <property name="dataSource" ref="dataSource" />    <property name="configLocation" value="classpath:configuration.xml"></property>     <property name="mapperLocations" value="classpath:com/xxx/mybatis/mapper/*.xml"/>     <property name="typeAliasesPackage" value="com.tiantian.mybatis.model" />   </bean>  

if (!isEmpty(this.mapperLocations)) {    for (Resource mapperLocation : this.mapperLocations) {     if (mapperLocation == null) {      continue;     }      try {      XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(),        configuration, mapperLocation.toString(), configuration.getSqlFragments());      xmlMapperBuilder.parse();     } catch (Exception e) {      throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", e);     } finally {      ErrorContext.instance().reset();     }      if (logger.isDebugEnabled()) {      logger.debug("Parsed mapper file: '" + mapperLocation + "'");     }    }   } 

public XMLMapperBuilder(Reader reader, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {   this(new XPathParser(reader, true, configuration.getVariables(), new XMLMapperEntityResolver()),     configuration, resource, sqlFragments);  } private XMLMapperBuilder(XPathParser parser, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {   super(configuration);   this.builderAssistant = new MapperBuilderAssistant(configuration, resource);   this.parser = parser;   this.sqlFragments = sqlFragments;   this.resource = resource;  } 

public void parse() {   //如果configuration对象还没加载xml配置文件（避免重复加载，实际上是确认是否解析了mapper节点的属性及内容，   //为解析它的子节点如cache、sql、select、resultMap、parameterMap等做准备），   //则从输入流中解析mapper节点，然后再将resource的状态置为已加载   if (!configuration.isResourceLoaded(resource)) {    configurationElement(parser.evalNode("/mapper"));    configuration.addLoadedResource(resource);    bindMapperForNamespace();   }   //解析在configurationElement函数中处理resultMap时其extends属性指向的父对象还没被处理的<resultMap>节点   parsePendingResultMaps();   //解析在configurationElement函数中处理cache-ref时其指向的对象不存在的<cache>节点(如果cache-ref先于其指向的cache节点加载就会出现这种情况)   parsePendingChacheRefs();   //同上，如果cache没加载的话处理statement时也会抛出异常   parsePendingStatements();  } 

private void configurationElement(XNode context) {   try {    //获取mapper节点的namespace属性    String namespace = context.getStringAttribute("namespace");    if (namespace.equals("")) {     throw new BuilderException("Mapper's namespace cannot be empty");    }    //设置当前namespace    builderAssistant.setCurrentNamespace(namespace);    //解析mapper的<cache-ref>节点    cacheRefElement(context.evalNode("cache-ref"));    //解析mapper的<cache>节点    cacheElement(context.evalNode("cache"));    //解析mapper的<parameterMap>节点    parameterMapElement(context.evalNodes("/mapper/parameterMap"));    //解析mapper的<resultMap>节点    resultMapElements(context.evalNodes("/mapper/resultMap"));    //解析mapper的<sql>节点    sqlElement(context.evalNodes("/mapper/sql"));    //使用XMLStatementBuilder的对象解析mapper的<select>、<insert>、<update>、<delete>节点,    //mybaits会使用MappedStatement.Builder类build一个MappedStatement对象,    //所以mybaits中一个sql对应一个MappedStatement    buildStatementFromContext(context.evalNodes("select|insert|update|delete"));   } catch (Exception e) {    throw new BuilderException("Error parsing Mapper XML. Cause: " + e, e);   }  } 

public void parseStatementNode() {   //ID属性   String id = context.getStringAttribute("id");   //databaseId属性   String databaseId = context.getStringAttribute("databaseId");    if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {    return;   }   //fetchSize属性   Integer fetchSize = context.getIntAttribute("fetchSize");   //timeout属性   Integer timeout = context.getIntAttribute("timeout");   //parameterMap属性   String parameterMap = context.getStringAttribute("parameterMap");   //parameterType属性   String parameterType = context.getStringAttribute("parameterType");   Class<?> parameterTypeClass = resolveClass(parameterType);   //resultMap属性   String resultMap = context.getStringAttribute("resultMap");   //resultType属性   String resultType = context.getStringAttribute("resultType");   //lang属性   String lang = context.getStringAttribute("lang");   LanguageDriver langDriver = getLanguageDriver(lang);    Class<?> resultTypeClass = resolveClass(resultType);   //resultSetType属性   String resultSetType = context.getStringAttribute("resultSetType");   StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));   ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);    String nodeName = context.getNode().getNodeName();   SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));   //是否是<select>节点   boolean isSelect = sqlCommandType == SqlCommandType.SELECT;   //flushCache属性   boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);   //useCache属性   boolean useCache = context.getBooleanAttribute("useCache", isSelect);   //resultOrdered属性   boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);    // Include Fragments before parsing   XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);   includeParser.applyIncludes(context.getNode());    // Parse selectKey after includes and remove them.   processSelectKeyNodes(id, parameterTypeClass, langDriver);      // Parse the SQL (pre: <selectKey> and <include> were parsed and removed)   SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);   //resultSets属性   String resultSets = context.getStringAttribute("resultSets");   //keyProperty属性   String keyProperty = context.getStringAttribute("keyProperty");   //keyColumn属性   String keyColumn = context.getStringAttribute("keyColumn");   KeyGenerator keyGenerator;   String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX;   keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true);   if (configuration.hasKeyGenerator(keyStatementId)) {    keyGenerator = configuration.getKeyGenerator(keyStatementId);   } else {    //useGeneratedKeys属性    keyGenerator = context.getBooleanAttribute("useGeneratedKeys",      configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType))      ? new Jdbc3KeyGenerator() : new NoKeyGenerator();   }    builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,     fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,     resultSetTypeEnum, flushCache, useCache, resultOrdered,      keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);  }