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Mybatis3源碼分析(05)-加載Configuration-加載MappedStatement 博客分類： java mybatis

MappedStatement說明

一個MappedStatement對象對應Mapper配置文件中的一個select/update/insert/delete節點，主要描述的是一條SQL語句。其屬性有 [java] view plain copy

//節點中的id屬性加要命名空間??

private?String?id;??

//直接從節點屬性中取??

private?Integer?fetchSize;??

//直接從節點屬性中取??

private?Integer?timeout;??

private?StatementType?statementType;??

private?ResultSetType?resultSetType;??

//對應一條SQL語句??

private?SqlSource?sqlSource;??

??

//每條語句都對就一個緩存，如果有的話。??

private?Cache?cache;??

//這個已經過時了??

private?ParameterMap?parameterMap;??

private?List<ResultMap>?resultMaps;??

private?boolean?flushCacheRequired;??

private?boolean?useCache;??

private?boolean?resultOrdered;??

//SQL的類型,select/update/insert/detete??

private?SqlCommandType?sqlCommandType;??

private?KeyGenerator?keyGenerator;??

private?String[]?keyProperties;??

private?String[]?keyColumns;??

??

//是否有內映射??

private?boolean?hasNestedResultMaps;??

private?String?databaseId;??

private?Log?statementLog;??

private?LanguageDriver?lang;??

private?String[]?resultSets;??

上面屬性都比較簡單，復雜的是SqlSource,下面有詳細的描述！

XMLStatementBuilder.parseStatementNode()方法

resultMap元素的解析已經分析完畢。與resultMap不一樣，XmlMapperBuilder在解析select/update /insert/delete的元素時會創建一個XMLStatementBuilder對象，解析的工作交由其方法 parseStatementNode()方法完成。 [java] view plain copy

private?void?buildStatementFromContext(List<XNode>?list,?String?requiredDatabaseId)?{??

????for?(XNode?context?:?list)?{??

??????//一個select/update/insert/delete元素創建一個XMLStatementBuilder對象??

??????final?XMLStatementBuilder?statementParser?=?new?XMLStatementBuilder(configuration,?builderAssistant,?context,?requiredDatabaseId);??

??????try?{??

????????//將元素解析成MappedStatemenet對象，并加入到Configuration中去??

????????statementParser.parseStatementNode();??

??????}?catch?(IncompleteElementException?e)?{??

????????configuration.addIncompleteStatement(statementParser);??

??????}??

????}??

如下是parseStatementNode()方法的代碼 [java] view plain copy

public?void?parseStatementNode()?{??

????String?id?=?context.getStringAttribute("id");??

????String?databaseId?=?context.getStringAttribute("databaseId");??

??

????if?(!databaseIdMatchesCurrent(id,?databaseId,?this.requiredDatabaseId))?return;??

??

????Integer?fetchSize?=?context.getIntAttribute("fetchSize");??

????Integer?timeout?=?context.getIntAttribute("timeout");??

????String?parameterMap?=?context.getStringAttribute("parameterMap");??

????String?parameterType?=?context.getStringAttribute("parameterType");??

????Class<?>?parameterTypeClass?=?resolveClass(parameterType);??

????String?resultMap?=?context.getStringAttribute("resultMap");??

????String?resultType?=?context.getStringAttribute("resultType");??

????String?lang?=?context.getStringAttribute("lang");??

????LanguageDriver?langDriver?=?getLanguageDriver(lang);??

??

????Class<?>?resultTypeClass?=?resolveClass(resultType);??

????String?resultSetType?=?context.getStringAttribute("resultSetType");??

????//Statement的類型，對應jdbc里的三個類型:Statement、PreparedStatement、CallableStatement，默認使用PreparedStatement??

????StatementType?statementType?=?StatementType.valueOf(context.getStringAttribute("statementType",?StatementType.PREPARED.toString()));??

????//這個也是跟jdbc里相對應的，一般采用默認即可??

????ResultSetType?resultSetTypeEnum?=?resolveResultSetType(resultSetType);??

?????

????//Sql的類型，select/update/insert/delete??

????String?nodeName?=?context.getNode().getNodeName();??

????SqlCommandType?sqlCommandType?=?SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));??

????boolean?isSelect?=?sqlCommandType?==?SqlCommandType.SELECT;??

????//是否刷新緩存??

????boolean?flushCache?=?context.getBooleanAttribute("flushCache",?!isSelect);??

????//是否使用緩存??

????boolean?useCache?=?context.getBooleanAttribute("useCache",?isSelect);??

????boolean?resultOrdered?=?context.getBooleanAttribute("resultOrdered",?false);??

??

????//不做分析??

????//?Include?Fragments?before?parsing??

????XMLIncludeTransformer?includeParser?=?new?XMLIncludeTransformer(configuration,?builderAssistant);??

????includeParser.applyIncludes(context.getNode());??

????//不做分析??

????//?Parse?selectKey?after?includes?and?remove?them.??

????processSelectKeyNodes(id,?parameterTypeClass,?langDriver);??

??????

????//生成SqlSource對象，這個對象非常重要，接下來詳細分析??

????//?Parse?the?SQL?(pre:?<selectKey>?and?<include>?were?parsed?and?removed)??

????SqlSource?sqlSource?=?langDriver.createSqlSource(configuration,?context,?parameterTypeClass);??

????String?resultSets?=?context.getStringAttribute("resultSets");??

????String?keyProperty?=?context.getStringAttribute("keyProperty");??

????String?keyColumn?=?context.getStringAttribute("keyColumn");??

??????

????//自動生成key，這里也不做討論??

????KeyGenerator?keyGenerator;??

????String?keyStatementId?=?id?+?SelectKeyGenerator.SELECT_KEY_SUFFIX;??

????keyStatementId?=?builderAssistant.applyCurrentNamespace(keyStatementId,?true);??

????if?(configuration.hasKeyGenerator(keyStatementId))?{??

??????keyGenerator?=?configuration.getKeyGenerator(keyStatementId);??

????}?else?{??

??????keyGenerator?=?context.getBooleanAttribute("useGeneratedKeys",??

??????????configuration.isUseGeneratedKeys()?&&?SqlCommandType.INSERT.equals(sqlCommandType))??

????????????new?Jdbc3KeyGenerator()?:?new?NoKeyGenerator();??

????}??

????//生成MappedStatement對象，并加到Configuration中??

????builderAssistant.addMappedStatement(id,?sqlSource,?statementType,?sqlCommandType,??

????????fetchSize,?timeout,?parameterMap,?parameterTypeClass,?resultMap,?resultTypeClass,??

????????resultSetTypeEnum,?flushCache,?useCache,?resultOrdered,???

????????keyGenerator,?keyProperty,?keyColumn,?databaseId,?langDriver,?resultSets);??

??}??

上在方法里附件解析一些基本的屬性外還有兩個主要的部分

SqlSource的構建過程
[java] view plain copy

SqlSource?sqlSource?=?langDriver.createSqlSource(configuration,?context,?parameterTypeClass);??

MappedStatement的構建過程 [java] view plain copy

builderAssistant.addMappedStatement(id,?sqlSource,?statementType,?sqlCommandType,??

???????fetchSize,?timeout,?parameterMap,?parameterTypeClass,?resultMap,?resultTypeClass,??

???????resultSetTypeEnum,?flushCache,?useCache,?resultOrdered,???

???????keyGenerator,?keyProperty,?keyColumn,?databaseId,?langDriver,?resultSets);??

SqlSource構建過程

SqlSource接口

[java] view plain copy

/**?

?*?Represents?the?content?of?a?mapped?statement?read?from?an?XML?file?or?an?annotation.??

?*?It?creates?the?SQL?that?will?be?passed?to?the?database?out?of?the?input?parameter?received?from?the?user.?

?*?

?*?@author?Clinton?Begin?

?*/??

public?interface?SqlSource?{??

??

??BoundSql?getBoundSql(Object?parameterObject);??

??

}??

SqlSource表示從mapper.xml或注解中讀取的sql內容,該sql一般還不能都被直接執行,例如 [html] view plain copy

<select?id="selectUserDetail"?resultMap="detailUserResultMap">??

????<!--CDATA里內容會都解析成一個SqlSource對象-->??

????????????????<![CDATA[?

????????????select?user_id,user_name,user_type,cust_id?from?tf_f_user?a?where?a.user_id=#${userId}?

????????]]>/select>??

SqlSource只有一個方法:getBoundSql(paramenterObject),其中paramenterObject為運行sql里的實際參數

BoundSql

[java] view plain copy

/**?

?*?An?actual?SQL?String?got?form?an?{@link?SqlSource}?after?having?processed?any?dynamic?content.?

?*?The?SQL?may?have?SQL?placeholders?"?"?and?an?list?(ordered)?of?an?parameter?mappings??

?*?with?the?additional?information?for?each?parameter?(at?least?the?property?name?of?the?input?object?to?read??

?*?the?value?from).??

?*?</br>?

?*?Can?also?have?additional?parameters?that?are?created?by?the?dynamic?language?(for?loops,?bind...).?

?*/??

/**?

?*?@author?Clinton?Begin?

?*/??

public?class?BoundSql?{??

??

??private?String?sql;??

??private?List<ParameterMapping>?parameterMappings;??

??private?Object?parameterObject;??

??private?Map<String,?Object>?additionalParameters;??

??private?MetaObject?metaParameters;??

??

??public?BoundSql(Configuration?configuration,?String?sql,?List<ParameterMapping>?parameterMappings,?Object?parameterObject)?{??

????this.sql?=?sql;??

????this.parameterMappings?=?parameterMappings;??

????this.parameterObject?=?parameterObject;??

????this.additionalParameters?=?new?HashMap<String,?Object>();??

????this.metaParameters?=?configuration.newMetaObject(additionalParameters);??

??}??

??

??public?String?getSql()?{??

????return?sql;??

??}??

??

??public?List<ParameterMapping>?getParameterMappings()?{??

????return?parameterMappings;??

??}??

??

??public?Object?getParameterObject()?{??

????return?parameterObject;??

??}??

??

??public?boolean?hasAdditionalParameter(String?name)?{??

????return?metaParameters.hasGetter(name);??

??}??

??

??public?void?setAdditionalParameter(String?name,?Object?value)?{??

????metaParameters.setValue(name,?value);??

??}???

??

??public?Object?getAdditionalParameter(String?name)?{??

????return?metaParameters.getValue(name);???

??}??

}??

??????

SqlBound代碼并不多，就是一個普通的java對象，有兩個屬性非常重要

sql:看代碼里的注解，這個sql已經是經過了一些處理，可以被jdbc執行的了。xml里配置的sql可能有占位符#{username},這里的sql占位符已經被替換成"?"號了。

parameterMappings:執行sql對象的實際的參數。由此可以判斷，每執行一條sql都會創建一個BoundSql對象。

SqlSource和BoundSql本身并不復雜，復雜的是這兩個對象被創建的過程。

LanguageDriver

SqlSource對象是通過LanguageDriver對象構建的，在mapper.xml配置sql里可以通過lang屬性指定一個 LanguageDriver，但我們通常不會這樣子做。當lang屬性沒有配置時，Mybatis會屬性默認給一個。這個默認的 LanguageDriver在Configuration的構造方法中定義的: [java] view plain copy

public?Configuration()?{??

????...??

????languageRegistry.setDefaultDriverClass(XMLLanguageDriver.class);??

????languageRegistry.register(RawLanguageDriver.class);??

??}??

馬上來看XMLLanguageDriver.createSqlSource()方法 [java] view plain copy

public?SqlSource?createSqlSource(Configuration?configuration,?XNode?script,?Class<?>?parameterType)?{??

????XMLScriptBuilder?builder?=?new?XMLScriptBuilder(configuration,?script,?parameterType);??

????return?builder.parseScriptNode();??

??}??

XMLScriptBuilder

XMLScriptBuilder.parseScriptNode()方法 [java] view plain copy

public?SqlSource?parseScriptNode()?{??

????//將一個sql內容解析成多個SqlNode??

????List<SqlNode>?contents?=?parseDynamicTags(context);??

????//將多個SqlNode組合一個SqlNode??

????MixedSqlNode?rootSqlNode?=?new?MixedSqlNode(contents);??

????SqlSource?sqlSource?=?null;??

????//判斷sql是否是動態的??

????if?(isDynamic)?{??

??????//生成動態的SqlSource??

??????sqlSource?=?new?DynamicSqlSource(configuration,?rootSqlNode);??

????}?else?{??

??????//生成靜態的SqlSource??

??????sqlSource?=?new?RawSqlSource(configuration,?rootSqlNode,?parameterType);??

????}??

????return?sqlSource;??

??}??

再看parseDynamicTagS(context)方法 [java] view plain copy

private?List<SqlNode>?parseDynamicTags(XNode?node)?{??

????//一個sql會被解析成多個SqlNode，稍后會有示例詳細說明??

????List<SqlNode>?contents?=?new?ArrayList<SqlNode>();??

????NodeList?children?=?node.getNode().getChildNodes();??

????for?(int?i?=?0;?i?<?children.getLength();?i++)?{??

??????XNode?child?=?node.newXNode(children.item(i));??

??????if?(child.getNode().getNodeType()?==?Node.CDATA_SECTION_NODE?||?child.getNode().getNodeType()?==?Node.TEXT_NODE)?{??

????????//如果這個Node只包含文本??

????????String?data?=?child.getStringBody("");??

????????//生成一個TextSqlNode??

????????TextSqlNode?textSqlNode?=?new?TextSqlNode(data);??

????????//判斷是否是動態的,如果文本里包含占位符，如#{username}或{table_name},isDynamic()方法就會返回true??

????????if?(textSqlNode.isDynamic())?{??

??????????contents.add(textSqlNode);??

??????????isDynamic?=?true;??

????????}?else?{??

??????????contents.add(new?StaticTextSqlNode(data));??

????????}??

??????}?else?if?(child.getNode().getNodeType()?==?Node.ELEMENT_NODE)?{?//?issue?#628??

????????//如果是有xml標簽的Node,交由Handler處理，同時被認為是動態的??

????????String?nodeName?=?child.getNode().getNodeName();??

????????NodeHandler?handler?=?nodeHandlers.get(nodeName);??

????????if?(handler?==?null)?{??

??????????throw?new?BuilderException("Unknown?element?<"?+?nodeName?+?">?in?SQL?statement.");??

????????}??

????????handler.handleNode(child,?contents);??

??????

????????isDynamic?=?true;??

??????}??

????}??

????return?contents;??

??}??

再看看nodeHandlers都有那些 [java] view plain copy

private?Map<String,?NodeHandler>?nodeHandlers?=?new?HashMap<String,?NodeHandler>()?{??

????private?static?final?long?serialVersionUID?=?7123056019193266281L;??

??

????{??

??????//Mybatis3動態sql都支持那些配置，這里就很清楚啦??

??????put("trim",?new?TrimHandler());??

??????put("where",?new?WhereHandler());??

??????put("set",?new?SetHandler());??

??????put("foreach",?new?ForEachHandler());??

??????put("if",?new?IfHandler());??

??????put("choose",?new?ChooseHandler());??

??????put("when",?new?IfHandler());??

??????put("otherwise",?new?OtherwiseHandler());??

??????put("bind",?new?BindHandler());??

????}??

??};??

看到這里基本上能了解sql是怎么被解析的啦！舉例說明: [html] view plain copy

<select?id="selectUserDetail"?resultMap="detailUserResultMap">??

????????<![CDATA[?

????????????select?user_id,user_name,user_type,cust_id?--這里一行會解析成一個StaticTextSqlNode?

????????????????from?tf_f_user?a?--這里一行也會解析成一個StaticTextSqlNode?

????????????????where?a.user_id=#{userId}?--這行會被解析成TextSqlNode,并且isDynamic被設置成true,因為有占位符?

??????????????????????????????????????????--這個空行也解析成一個StaticTextSqlNode?

????????]]><!--?這四個SqlNode會被組合成一個MixedSqlNode?-->??

????</select>??

再來個動態sql的: [html] view plain copy

<select?id="selectUserDetail"?resultMap="detailUserResultMap">??

????????<![CDATA[?

????????????select?user_id,user_name,user_type,cust_id?--這里一行會解析成一個StaticTextSqlNode?

????????????????from?tf_f_user?a?--這里一行也會解析成一個StaticTextSqlNode?

????????????????where?a.user_id=#{userId}?--這行會被解析成TextSqlNode,并且isDynamic被設置成true,因為有占位符?

??????????????????????????????????????????--這個空行也解析成一個StaticTextSqlNode?

????????]]>??

????????<if?test="user_name!=null">?<!--?這個標簽里的內容會交給IfHandler處理?-->??

????????????and?--這里的解析與上行的一樣，解析成一個StaticTextSqlNode??

????????????user_name=#{userName}?--這里的解析與上行的一樣，也會被解析成一個TextSqlNode,并且isDynamic被設置成true,因為有占位符??

????????</if><!--?IfHandler會將這里面的內個SqlNode組成MixedSqlNode再組成一個IfSqlNode?-->??

????</select><!--?這五個SqlNode會被組合成一個MixedSqlNode?-->??

附上IfHandler的代碼 [java] view plain copy

private?class?IfHandler?implements?NodeHandler?{??

????public?void?handleNode(XNode?nodeToHandle,?List<SqlNode>?targetContents)?{??

??????//解析子節點??

??????List<SqlNode>?contents?=?parseDynamicTags(nodeToHandle);??

??????//組合??

??????MixedSqlNode?mixedSqlNode?=?new?MixedSqlNode(contents);??

??????String?test?=?nodeToHandle.getStringAttribute("test");??

??????//生成IfSqlNode??

??????IfSqlNode?ifSqlNode?=?new?IfSqlNode(mixedSqlNode,?test);??

??????targetContents.add(ifSqlNode);??

????}??

??}??

其他的nodeHandler在這里就不討論了，實現方式與IfHandler差不多。如下兩個方法也不在這里做討論

SqlSource.getBoundSql()方法

SqlNode.apply(DynamicContextcontext)方法

?

http://blog.csdn.net/ashan_li/article/details/50351080

轉載于:https://my.oschina.net/xiaominmin/blog/1599100

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