关于mybatis的执行流程和源码
select * from user where name =? and pwd=?
1. statement:select * from user where name = and pwd=(采用直接拼接的方式，有sql注入的风险)
2. preparestatement:
**~.setString(1,'name') ~.setString(2,'pwd')**
select * from user where name =‘${name}’ and pwd='‘${pwd}’'
(采用String拼接的方式，没有sql注入的风险)
解析config.xml、mapper.xml:
@Before public static void initFactory() { try { SqlSession session = null; String resource = "configuration.xml"; // 使用io流读取配置 InputStream inputStream; inputStream = Resources.getResourceAsStream(resource); //这里是解析配置文件 sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); // 得到了一个会话，有了这个会话，你就可以对数据进行增，删，改，查的操作 session = sqlSessionFactory.openSession(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } =======》new SqlSessionFactoryBuilder().build(inputStream); return build(inputStream, null, null); XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties); return build(parser.parse()); if (parsed) { throw new BuilderException("Each XMLConfigBuilder can only be used once."); } parsed = true; parseConfiguration(parser.evalNode("/configuration"));//解析节点 //全局的配置文件就会被解析成一个org.apache.ibatis.session.Configuration return configuration; ====parser.parse()调用========》parseConfiguration(parser.evalNode("/configuration"));//解析节点 private void parseConfiguration(XNode root) { try { //issue #117 read properties first propertiesElement(root.evalNode("properties")); Properties settings = settingsAsProperties(root.evalNode("settings")); loadCustomVfs(settings); loadCustomLogImpl(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")); mapperElement(root.evalNode("mappers"));//解析mapper节点 } catch (Exception e) { throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e); } } /** *mapper接口的方法同时又xml配置和注解配置的话会报错 *xml配置和注解配置都会被mybatis翻译成MappedStatement对象（两个mappedStatement的id相同(就是方法名)，用的缓存容器是Hashmap(继承了hashmap的一个StateMap，重写了put())所以会报错） *<mappers> //如何只找到mapper文件的(mapper接口+*mapper.xml) <package name="mapper" /> <!-- <mapper class="" resource="" url=""/> --> </mappers> */ =============》 mapperElement(root.evalNode("mappers"));//解析mapper节点 private void mapperElement(XNode parent) throws Exception { if (parent != null) { for (XNode child : parent.getChildren()) { //解析mapper/package节点 if ("package".equals(child.getName())) { String mapperPackage = child.getStringAttribute("name"); configuration.addMappers(mapperPackage);//各种各样的mapper文件 } else { String resource = child.getStringAttribute("resource"); String url = child.getStringAttribute("url"); String mapperClass = child.getStringAttribute("class"); //解析你写的<mapper>注解的这三个属性(看源码可以看出这三个属性你只能配置一个属性) /** *resource/url是资源定位符（就是路径） * mapperClass你直接指定了一个接口 */ if (resource != null && url == null && mapperClass == null) { //配置了resource 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) { //配置了url ErrorContext.instance().resource(url); InputStream inputStream = Resources.getUrlAsStream(url);//拿到mapper.xml文件的输入流 XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments()); mapperParser.parse();//解析 } else if (resource == null && url == null && mapperClass != null) { //配置了mapperClass(直接拿接口了) 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."); } } } } } ===============》configuration.addMappers(mapperPackage);//各种各样的mapper文件 public void addMappers(String packageName, Class<?> superType) { ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<>(); resolverUtil.find(new ResolverUtil.IsA(superType), packageName); Set<Class<? extends Class<?>>> mapperSet = resolverUtil.getClasses(); for (Class<?> mapperClass : mapperSet) { addMapper(mapperClass);//干活的地方 } } public <T> void addMapper(Class<T> type) { if (type.isInterface()) {//拿接口 if (hasMapper(type)) {//验证你是不是有一个加载的mapper接口了 throw new BindingException("Type " + type + " is already known to the MapperRegistry."); } boolean loadCompleted = false; try { knownMappers.put(type, new MapperProxyFactory<>(type)); // It's important that the type is added before the parser is run // otherwise the binding may automatically be attempted by the // mapper parser. If the type is already known, it won't try. //解析接口(注解还是xml写的sql语句) MapperAnnotationBuilder parser = new MapperAnnotationBuilder(config, type); parser.parse(); loadCompleted = true; } finally { if (!loadCompleted) { knownMappers.remove(type); } } } } ============》parser.parse();//解析接口的注解 public void parse() { String resource = type.toString();//先拿接口的名字<mapper class="" url="" resource=""/> if (!configuration.isResourceLoaded(resource)) { loadXmlResource();//加载xml文件 configuration.addLoadedResource(resource); assistant.setCurrentNamespace(type.getName()); parseCache(); parseCacheRef(); Method[] methods = type.getMethods(); for (Method method : methods) { try { // issue #237 if (!method.isBridge()) { parseStatement(method); } } catch (IncompleteElementException e) { configuration.addIncompleteMethod(new MethodResolver(this, method)); } } } parsePendingMethods();//解析注解 } ==============》//parsePendingMethods();//解析注解 private void parsePendingMethods() { Collection<MethodResolver> incompleteMethods = configuration.getIncompleteMethods(); synchronized (incompleteMethods) { Iterator<MethodResolver> iter = incompleteMethods.iterator(); while (iter.hasNext()) { try { iter.next().resolve(); iter.remove(); } catch (IncompleteElementException e) { // This method is still missing a resource } } } } ========================》mapperx.xml文件的解析 public void parse() { if (!configuration.isResourceLoaded(resource)) {//判断是否解析过你这个文件了 configurationElement(parser.evalNode("/mapper")); configuration.addLoadedResource(resource); bindMapperForNamespace(); } parsePendingResultMaps(); parsePendingCacheRefs(); parsePendingStatements(); } ==========================》解析mapper的里面的节点，拿到里面的配置项，最终封装成一个MapperedStatement对象 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"));//解析你写的sql语句了，解析到一个list容器， } catch (Exception e) { throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e); } } ===========================》//buildStatementFromContext(context.evalNodes("select|insert|update|delete"));//解析你写的sql语句了，解析到一个list容器， private void buildStatementFromContext(List<XNode> list) { if (configuration.getDatabaseId() != null) { buildStatementFromContext(list, configuration.getDatabaseId());//那你配置的那个指定的databaseid } buildStatementFromContext(list, null);//开始循环遍历 } ===========================》//buildStatementFromContext(list, null);//开始循环遍历 private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) { //list表示Usermapper.xml的select|insert|update|delete节点 for (XNode context : list) { final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId); try { //具体解析 statementParser.parseStatementNode(); } catch (IncompleteElementException e) { //你写的sql语句有问题 configuration.addIncompleteStatement(statementParser); } } } ================================》//这个方法解析select|~|~|~节点的 public void parseStatementNode() { String id = context.getStringAttribute("id"); String databaseId = context.getStringAttribute("databaseId"); if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) { return; } String nodeName = context.getNode().getNodeName(); SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH)); boolean isSelect = sqlCommandType == SqlCommandType.SELECT; //刷新缓存:一级缓存二级缓存 boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect); boolean useCache = context.getBooleanAttribute("useCache", isSelect); boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false); // Include Fragments before parsing XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant); includeParser.applyIncludes(context.getNode()); String parameterType = context.getStringAttribute("parameterType"); Class<?> parameterTypeClass = resolveClass(parameterType); String lang = context.getStringAttribute("lang"); LanguageDriver langDriver = getLanguageDriver(lang); // Parse selectKey after includes and remove them. processSelectKeyNodes(id, parameterTypeClass, langDriver); // Parse the SQL (pre: <selectKey> and <include> were parsed and removed) 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)) ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE; } //解析sql 根据sql文本来判断是否需要动态解析(就是看你写了动态sql标签没<where>...) 如果没有动态sql语句且只有#{}表达式时 直接使用？静态解析占位 当有${}时不进行解析 /** 科普:<select lang="就是自己写的一个语言解析器"></select> mybatis支持自己写自定义的标签，但是在解析标签时你必须指定语言相对应的语言解析器 */ /** ${}---->动态的sql语句(dynamicSqlSource)---解析配置文件的时候不会动这个sql语句，执行是才会去除${}符号(sql注入问题风险) #{}---->静态的sql语句(staticSqlSource)---解析的时候会把他改成?占位符(会对自动传入的数据加一个""双引号)，mybatis官网有解释 */ SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass); StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString())); Integer fetchSize = context.getIntAttribute("fetchSize"); Integer timeout = context.getIntAttribute("timeout"); String parameterMap = context.getStringAttribute("parameterMap"); String resultType = context.getStringAttribute("resultType"); Class<?> resultTypeClass = resolveClass(resultType); String resultMap = context.getStringAttribute("resultMap"); String resultSetType = context.getStringAttribute("resultSetType"); ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType); if (resultSetTypeEnum == null) { resultSetTypeEnum = configuration.getDefaultResultSetType(); } String keyProperty = context.getStringAttribute("keyProperty"); String keyColumn = context.getStringAttribute("keyColumn"); String resultSets = context.getStringAttribute("resultSets"); //构造一个MappedStatement builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType, fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass, resultSetTypeEnum, flushCache, useCache, resultOrdered, keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets); } ======================》//构造一个MappedStatement builderAssistant.addMappedStatement public MappedStatement addMappedStatement( String id, SqlSource sqlSource, StatementType statementType, SqlCommandType sqlCommandType, Integer fetchSize, Integer timeout, String parameterMap, Class<?> parameterType, String resultMap, Class<?> resultType, ResultSetType resultSetType, boolean flushCache, boolean useCache, boolean resultOrdered, KeyGenerator keyGenerator, String keyProperty, String keyColumn, String databaseId, LanguageDriver lang, String resultSets) { if (unresolvedCacheRef) { throw new IncompleteElementException("Cache-ref not yet resolved"); } id = applyCurrentNamespace(id, false); boolean isSelect = sqlCommandType == SqlCommandType.SELECT; MappedStatement.Builder statementBuilder = new MappedStatement.Builder(configuration, id, sqlSource, sqlCommandType) .resource(resource) .fetchSize(fetchSize) .timeout(timeout) .statementType(statementType) .keyGenerator(keyGenerator) .keyProperty(keyProperty) .keyColumn(keyColumn) .databaseId(databaseId) .lang(lang) .resultOrdered(resultOrdered) .resultSets(resultSets) .resultMaps(getStatementResultMaps(resultMap, resultType, id)) .resultSetType(resultSetType) .flushCacheRequired(valueOrDefault(flushCache, !isSelect)) .useCache(valueOrDefault(useCache, isSelect)) .cache(currentCache); ParameterMap statementParameterMap = getStatementParameterMap(parameterMap, parameterType, id); if (statementParameterMap != null) { statementBuilder.parameterMap(statementParameterMap); } MappedStatement statement = statementBuilder.build(); configuration.addMappedStatement(statement);//将构建好的mapperedstatement文件添加到一个全局的配置文件中 return statement; }
解析sqlsessionFactory:
session = sqlSessionFactory.openSession(); ==========》//默认实现类org.apache.ibatis.session.defaults.DefaultSqlSessionFactory 然后调用openSessionFromDataSource private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) { Transaction tx = null; try { //通过解析到的configuration来获得environment标签 final Environment environment = configuration.getEnvironment(); //事物 final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment); tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit); final Executor executor = configuration.newExecutor(tx, execType); return new DefaultSqlSession(configuration, executor, autoCommit); } catch (Exception e) { closeTransaction(tx); // may have fetched a connection so lets call close() throw ExceptionFactory.wrapException("Error opening session. Cause: " + e, e); } finally { ErrorContext.instance().reset(); } }
mapper代理对象的执行流程:
CustomerMapper mapper = session.getMapper(CustomerMapper.class);该方法开始
科普1：接口参数不合法时(即mapper接口方法的的参数名与mapper.xml参数名不一致时)解决方法:
#{arg0}......#{argn}、#{param1}......#{paramn}、接口方法参数打@Param("参数名")注解
为什么这么设计(为什么有arg0):
JDK8之前，你拿参数名是拿不到的拿到的字符串是arg0;
JDK8之后，你映射参数时才能使用具体的方法名
为什么这么设计(为什么有param1):
mybatis框架设计时，需要思考我拿到用户参数时，写什么参数名，为了你一定有一个参数可以使用，param1就产生了
@SuppressWarnings("unchecked")
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
}
try {
return mapperProxyFactory.newInstance(sqlSession);//拿到代理的实例
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}
===============》//return mapperProxyFactory.newInstance(sqlSession);//拿到代理的实例
//MapperProxy实现了 InvocationHandler接口
//invoke方法就是sql具体的执行流程了
//我这是mybatis3.5.6的
@Override
public Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable {
return mapperMethod.execute(sqlSession, args);
}
}
===============》MapperMethed
public Object execute(SqlSession sqlSession, Object[] args) {
Object result;
switch (command.getType()) {
case INSERT: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.insert(command.getName(), param));
break;
}
case UPDATE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.update(command.getName(), param));
break;
}
case DELETE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.delete(command.getName(), param));
break;
}
case SELECT:
if (method.returnsVoid() && method.hasResultHandler()) {
executeWithResultHandler(sqlSession, args);
result = null;
} else if (method.returnsMany()) {
result = executeForMany(sqlSession, args);
} else if (method.returnsMap()) {
result = executeForMap(sqlSession, args);
} else if (method.returnsCursor()) {
result = executeForCursor(sqlSession, args);
} else {
//这行代码非常重要
Object param = method.convertArgsToSqlCommandParam(args);
result = sqlSession.selectOne(command.getName(), param);
if (method.returnsOptional()
&& (result == null || !method.getReturnType().equals(result.getClass()))) {
result = Optional.ofNullable(result);
}
}
break;
case FLUSH:
result = sqlSession.flushStatements();
break;
default:
throw new BindingException("Unknown execution method for: " + command.getName());
}
if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
throw new BindingException("Mapper method '" + command.getName()
+ " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
}
return result;
}
============》//method.convertArgsToSqlCommandParam(args);单一非特殊参数返回没有名字。 多个参数用的命名规则命名（就是这里提供了param1这种参数写法）主要针对sql语句的参数映射
public Object getNamedParams(Object[] args) {
final int paramCount = names.size();
if (args == null || paramCount == 0) {
return null;
} else if (!hasParamAnnotation && paramCount == 1) {
Object value = args[names.firstKey()];
return wrapToMapIfCollection(value, useActualParamName ? names.get(0) : null);
} else {
final Map<String, Object> param = new ParamMap<>();
int i = 0;
for (Map.Entry<Integer, String> entry : names.entrySet()) {
param.put(entry.getValue(), args[entry.getKey()]);
// add generic param names (param1, param2, ...)
final String genericParamName = GENERIC_NAME_PREFIX + (i + 1);
// ensure not to overwrite parameter named with @Param
if (!names.containsValue(genericParamName)) {
param.put(genericParamName, args[entry.getKey()]);
}
i++;
}
return param;
}
}
============》//select查询具体调用方法流程
public <T> T selectOne(String statement, Object parameter) {
// Popular vote was to return null on 0 results and throw exception on too many.
List<T> list = this.selectList(statement, parameter);//查询都是调用的selectList
if (list.size() == 1) {
return list.get(0);
} else if (list.size() > 1) {
throw new TooManyResultsException("Expected one result (or null) to be returned by selectOne(), but found: " + list.size());
} else {
return null;
}
}
===============》//调用selectList
@Override
public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
try {
MappedStatement ms = configuration.getMappedStatement(statement);
return executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error querying database. Cause: " + e, e);
} finally {
ErrorContext.instance().reset();
}
}
==========》//开始查询
@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
//sql语句就包装在这里面(走完这行代码:静态的sql语句没有赋值但是#{}改成了?，动态的sql语句已经赋值了)
BoundSql boundSql = ms.getBoundSql(parameterObject);
CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql);
return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
=========》query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
if (closed) {
throw new ExecutorException("Executor was closed.");
}
if (queryStack == 0 && ms.isFlushCacheRequired()) {
clearLocalCache();
}
List<E> list;
try {
queryStack++;
list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
if (list != null) {
//开始先在缓存中去查询
handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
} else {
//数据库中去查询
list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
}
} finally {
queryStack--;
}
if (queryStack == 0) {
for (DeferredLoad deferredLoad : deferredLoads) {
deferredLoad.load();
}
// issue #601
deferredLoads.clear();
if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
// issue #482
clearLocalCache();
}
}
return list;
}
===========》//去数据库查询
private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
List<E> list;
localCache.putObject(key, EXECUTION_PLACEHOLDER);
try {
//根据你指定的执行器去调用不同的方法(默认是simpleExecutor)
/**
三大执行器:
SimpleExecutor：每执行一次update或select，就开bai启一个Statement对象，用完立刻关闭Statement对象。
ReuseExecutor：执行update或select，以sql作为key查找Statement对象，存在就使用，不存在就创建，用完后，不关闭Statement对象，而是放置于Map<String, Statement>内，供下一次使用。简言之，就是重复使用Statement对象。
BatchExecutor：执行update（没有select，JDBC批处理不支持select），将所有sql都添加到批处理中（addBatch()），等待统一执行（executeBatch()），它缓存了多个Statement对象，每个Statement对象都是addBatch()完毕后，等待逐一执行executeBatch()批处理。与JDBC批处理相同。(使用时出现一种情况:我无法在他这个处理器的缓存中拿到我希望得到的id)
四大处理器:
StatementHandler：处理对象PrepareStatement
ParameterHandler：处理参数
ResultSetHandler：处理结果集
TypeHandler：类型转换
*/
list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
} finally {
localCache.removeObject(key);
}
localCache.putObject(key, list);
if (ms.getStatementType() == StatementType.CALLABLE) {
localOutputParameterCache.putObject(key, parameter);
}
return list;
}
================》//simpleExecutor的doQuery()
@Override
public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
Statement stmt = null;
try {
Configuration configuration = ms.getConfiguration();
StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
//这个就是JDBC使用preparestatement去查询数据了
stmt = prepareStatement(handler, ms.getStatementLog());
return handler.query(stmt, resultHandler);
} finally {
closeStatement(stmt);
}
}
===========》//jdbc
private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
Statement stmt;
Connection connection = getConnection(statementLog);
stmt = handler.prepare(connection, transaction.getTimeout());
//这里实现~.setString的()设置参数(调用的是RoutingStatementHandle)
handler.parameterize(stmt);
return stmt;
}
==========》//调用prepareStatement的parameterize方法
@Override
public void parameterize(Statement statement) throws SQLException {
parameterHandler.setParameters((PreparedStatement) statement);
}
==========》//调用defaultpreparestatementHandler的setParameters((PreparedStatement) statement);参数都存在parameterObject这个对象里(给问号赋值)----走完这个方法就是preparestatement已经完成赋值操作了
@Override
public void setParameters(PreparedStatement ps) {
ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
if (parameterMappings != null) {
//迭代参数对比参数名字和参数类型和参数顺序分别赋值
for (int i = 0; i < parameterMappings.size(); i++) {
ParameterMapping parameterMapping = parameterMappings.get(i);
if (parameterMapping.getMode() != ParameterMode.OUT) {
Object value;
String propertyName = parameterMapping.getProperty();
if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params
value = boundSql.getAdditionalParameter(propertyName);
} else if (parameterObject == null) {
value = null;
} else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
value = parameterObject;
} else {
MetaObject metaObject = configuration.newMetaObject(parameterObject);
value = metaObject.getValue(propertyName);
}
TypeHandler typeHandler = parameterMapping.getTypeHandler();
JdbcType jdbcType = parameterMapping.getJdbcType();
if (value == null && jdbcType == null) {
jdbcType = configuration.getJdbcTypeForNull();
}
try {
typeHandler.setParameter(ps, i + 1, value, jdbcType);
} catch (TypeException | SQLException e) {
throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);
}
}
}
}
}