首先是mybatis简单的使用Demo（源码基于3.5.1版本）:
String resource = "mybatis-config.xml";
InputStream inputStream = null;
try {
inputStream = Resources.getResourceAsStream(resource);
} catch (IOException e) {
e.printStackTrace();
}
//构建 SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//从 SqlSessionFactory 中获取 SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//获取接口代理对象
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//执行查询方法
User user = mapper.selectOne(1L);
System.out.println(user);
sqlSession.close();
一、构建 SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSessionFactoryBuilder.build()方法：
public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
try {
//xml配置文件的解析器
XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
//返回一个SqlSessionFactory的实现类DefaultSqlSessionFactory
return build(parser.parse());
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error building SqlSession.", e);
} finally {
ErrorContext.instance().reset();
try {
inputStream.close();
} catch (IOException e) {
// Intentionally ignore. Prefer previous error.
}
}
}
主要的方法parser.parse()：解析全局配置文件
//解析全局配置文件 将配置信息封装成一个Configuration
public Configuration parse() {
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
//解析配置文件的configuration标签节点，并将配置信息保存到Configuration对象
parseConfiguration(parser.evalNode("/configuration"));
//返回一个Configuration对象，包含了所有的全局配置信息和映射文件信息
return configuration;
}
parseConfiguration(parser.evalNode("/configuration"))：
//解析全局配置文件configuration标签的各子标签，并将配置信息保存到Configuration对象
private void parseConfiguration(XNode root) {
try {
//解析properties标签
propertiesElement(root.evalNode("properties"));
//解析settings标签，并封装成一个Properties
Properties settings = settingsAsProperties(root.evalNode("settings"));
loadCustomVfs(settings);
loadCustomLogImpl(settings);
//解析typeAliases标签
typeAliasesElement(root.evalNode("typeAliases"));
//解析plugins标签
pluginElement(root.evalNode("plugins"));
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
reflectorFactoryElement(root.evalNode("reflectorFactory"));
settingsElement(settings);
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));
//解析mappers标签
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
重点：解析配置文件的mappers标签（sql映射文件位置） mapperElement(root.evalNode("mappers"))：
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
//遍历<mappers>子标签：
for (XNode child : parent.getChildren()) {
//使用<package name="org.mybatis.builder"/>子标签
if ("package".equals(child.getName())) {
String mapperPackage = child.getStringAttribute("name");
//保存包名
configuration.addMappers(mapperPackage);
} else {
//<mapper>
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
String mapperClass = child.getStringAttribute("class");
// <mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
if (resource != null && url == null && mapperClass == null) {
ErrorContext.instance().resource(resource);
//获取映射文件流
InputStream inputStream = Resources.getResourceAsStream(resource);
//映射文件解析器
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
//解析映射文件
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.");
}
}
}
}
}
解析sql映射文件mapperParser.parse()：
public void parse() {
//该映射文件是否已经加载过
if (!configuration.isResourceLoaded(resource)) {
//解析映射文件的mapper标签
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
bindMapperForNamespace();
}
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}
解析sql映射文件的mapper标签，configurationElement(parser.evalNode("/mapper"))：
//解析mapper的各个子标签信息并保存在Configuration中
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"));
//解析所有的增删改查四大标签
buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
} catch (Exception e) {
throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
}
}
解析增删改查标签buildStatementFromContext(context.evalNodes("select|insert|update|delete"))：
private void buildStatementFromContext(List<XNode> list) {
//如果标签有指定databaseId
if (configuration.getDatabaseId() != null) {
buildStatementFromContext(list, configuration.getDatabaseId());
}
buildStatementFromContext(list, null);
}
接下来buildStatementFromContext(list, null):
private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
//遍历所有select|insert|update|delete标签
for (XNode context : list) {
//Statement（代表一个增删改查标签）解析器
final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
try {
//解析标签
statementParser.parseStatementNode();
} catch (IncompleteElementException e) {
configuration.addIncompleteStatement(statementParser);
}
}
}
解析每增删改查标签 statementParser.parseStatementNode()：
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;
//是否清空缓存，不设置的话 select标签默认为false，其他三个都为为true
boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
//是否使用二级缓存，不设置的话 select标签默认为true，其他三个都为为false
boolean useCache = context.getBooleanAttribute("useCache", isSelect);
boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);
//解析include标签，将sql片段包含进来
XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
includeParser.applyIncludes(context.getNode());
//参数类型
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;
}
SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);
//Statement类型，STATEMENT：普通的字符串拼接, PREPARED（默认）：sql预处理, CALLABLE：可以使用存储过程
StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
//下面都是些获取相应的标签属性值
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);
String keyProperty = context.getStringAttribute("keyProperty");
String keyColumn = context.getStringAttribute("keyColumn");
String resultSets = context.getStringAttribute("resultSets");
//每一个增删改查标签信息最终都会被封装成一个MappedStatement并保存在configuration中
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}
二、从 SqlSessionFactory 中获取 SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
openSession()-->openSessionFromDataSource:
private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
Transaction tx = null;
try {
final Environment environment = configuration.getEnvironment();
final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
//创建事务对象
tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
//创建执行器Executor
final Executor executor = configuration.newExecutor(tx, execType);
//创建DefaultSqlSession，包含configuration，executor
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();
}
}
创建执行器Executor，configuration.newExecutor(tx, execType)：
public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
executorType = executorType == null ? defaultExecutorType : executorType;
executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
Executor executor;
//根据Executor在全局配置文件中的类型，创建SimpleExecutor（默认）/BatchExecutor/ReuseExecutor
if (ExecutorType.BATCH == executorType) {
executor = new BatchExecutor(this, transaction);
} else if (ExecutorType.REUSE == executorType) {
executor = new ReuseExecutor(this, transaction);
} else {
executor = new SimpleExecutor(this, transaction);
}
//如果开启了二级缓存，则创建CachingExecutor来包装executor
if (cacheEnabled) {
executor = new CachingExecutor(executor);
}
//使用每一个拦截器包装executor
executor = (Executor) interceptorChain.pluginAll(executor);
return executor;
}
三、SqlSession.getMapper():返回接口的代理对象
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
getMapper:
public <T> T getMapper(Class<T> type) {
//从configuration对象中获取
return configuration.getMapper(type, this);
}
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
return mapperRegistry.getMapper(type, sqlSession);
}
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
//根据接口类型在knownMappers中获取对应得MapperProxyFactory
final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
}
try {
//创建代理对象
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}
public T newInstance(SqlSession sqlSession) {
//MapperProxy实现了InvocationHandler接口,包含sqlSession（包含configuration，executor）
final MapperProxy<T> mapperProxy = new MapperProxy<>(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
protected T newInstance(MapperProxy<T> mapperProxy) {
//利用jdk动态代理创建代理对象
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
}
四、执行查询方法：
User user = mapper.selectOne(1L);
mapper是一个代理对象，实际是执行MapperProxy（implements InvocationHandler)的invoke方法：
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
if (Object.class.equals(method.getDeclaringClass())) {
//直接执行Object对象中定义的方法
return method.invoke(this, args);
//是否是接口的默认方法（jdk1.8）
} else if (isDefaultMethod(method)) {
return invokeDefaultMethod(proxy, method, args);
}
} catch (Throwable t) {
throw ExceptionUtil.unwrapThrowable(t);
}
//MapperMethod代表当前执行的方法，包含了configuration对象
final MapperMethod mapperMethod = cachedMapperMethod(method);
//执行增删改查方法
return mapperMethod.execute(sqlSession, args);
}
cachedMapperMethod（method）:
private MapperMethod cachedMapperMethod(Method method) {
//先从methodCache中获取，如果不存在就new一个MapperMethod添加到methodCache并返回
return methodCache.computeIfAbsent(method, k -> new MapperMethod(mapperInterface, method, sqlSession.getConfiguration()));
}
mapperMethod.execute(sqlSession, args)：执行具体的增删改方法
public Object execute(SqlSession sqlSession, Object[] args) {
Object result;
//判断执行sql语言的类型，这里是select类型
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:
//方法无返回值
if (method.returnsVoid() && method.hasResultHandler()) {
executeWithResultHandler(sqlSession, args);
result = null;
//返回值为集合时
} else if (method.returnsMany()) {
result = executeForMany(sqlSession, args);
//返回值为Map时
} else if (method.returnsMap()) {
result = executeForMap(sqlSession, args);
//返回值为游标
} else if (method.returnsCursor()) {
result = executeForCursor(sqlSession, args);
} else {
//返回值为单个
//将方法参数转换成sql语言可以使用的形式
Object param = method.convertArgsToSqlCommandParam(args);
//查询单条记录command.getName()为方法的全限定名
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() + ").");
}
//返回结果
return result;
}
method.convertArgsToSqlCommandParam(args)：参数解析
public Object convertArgsToSqlCommandParam(Object[] args) {
return paramNameResolver.getNamedParams(args);
}
public Object getNamedParams(Object[] args) {
//参数的数量
final int paramCount = names.size();
if (args == null || paramCount == 0) {
return null;
//如果方法参数没有使用@Param注解命名，且方法只有一个参数，直接返回该参数值
} else if (!hasParamAnnotation && paramCount == 1) {
return args[names.firstKey()];
} else {
//如果是多个参数则封装成一个Map
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 + String.valueOf(i + 1);
// ensure not to overwrite parameter named with @Param
if (!names.containsValue(genericParamName)) {
param.put(genericParamName, args[entry.getKey()]);
}
i++;
}
return param;
}
}
sqlSession.selectOne(command.getName(), param):查询单条记录
@Override
public <T> T selectOne(String statement, Object parameter) {
// 查询单条其实也是和查询多条记录一样返回List,再取第一条
List<T> list = this.selectList(statement, parameter);
if (list.size() == 1) {
return list.get(0);
} else if (list.size() > 1) {
//如果查到多条记录就报错
throw new TooManyResultsException("Expected one result (or null) to be returned by selectOne(), but found: " + list.size());
} else {
return null;
}
}
selectList(statement, parameter)：
@Override
public <E> List<E> selectList(String statement, Object parameter) {
return this.selectList(statement, parameter, RowBounds.DEFAULT);
}
@Override
public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
try {
//configuration中获取到MappedStatement（代表一个增删改查标签的所有信息）
MappedStatement ms = configuration.getMappedStatement(statement);
//执行器执行查询操作，wrapCollection(parameter)处理参数是集合的情况
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();
}
}
executor.query（）：
//CachingExecutor:
@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
//BoundSql 代表sql的详细信息，包括sql语言，参数值以及参数在sql语句中的映射关系
BoundSql boundSql = ms.getBoundSql(parameterObject);
//使用了二级缓存，所有需要生成缓存的key
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 parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
throws SQLException {
//如果映射文件使用了 </cache>标签 ,就能获取到缓存对象
Cache cache = ms.getCache();
if (cache != null) {
flushCacheIfRequired(ms);
if (ms.isUseCache() && resultHandler == null) {
ensureNoOutParams(ms, boundSql);
@SuppressWarnings("unchecked")
//先从缓存中获取，存在就直接返回，不存在再查询
List<E> list = (List<E>) tcm.getObject(cache, key);
if (list == null) {
//delegate，就是真正执行sql的Executor（当前为）,CachingExecutor只是对其的一层包装
list = delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
tcm.putObject(cache, key, list); // issue #578 and #116
}
return list;
}
}
return delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql)：
//BaseExecutor：
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.");
}
//是否需要清本地缓存
if (queryStack == 0 && ms.isFlushCacheRequired()) {
clearLocalCache();
}
List<E> list;
try {
queryStack++;
//先从本地缓存中获取
list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
if (list != null) {
handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
} else {
//缓存不存在，再从数据库中查
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;
}
queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql)：
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 {
//从数据库中查
list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
} finally {
localCache.removeObject(key);
}
//将查到的结果放入本地缓存
localCache.putObject(key, list);
if (ms.getStatementType() == StatementType.CALLABLE) {
localOutputParameterCache.putObject(key, parameter);
}
return list;
}
doQuery(ms, parameter, rowBounds, resultHandler, boundSql)：
@Override
public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
//原生jdbc的Statement
Statement stmt = null;
try {
Configuration configuration = ms.getConfiguration();
//StatementHandler(用于获取Statement)
StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
//获取PreparedStatement
stmt = prepareStatement(handler, ms.getStatementLog());
//执行sql,返回结果集
return handler.query(stmt, resultHandler);
} finally {
closeStatement(stmt);
}
}
configuration.newStatementHandler(...):获取StatementHandler对象
public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
//RoutingStatementHandler是一个包装对象
StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
//使用每一个拦截器包装statementHandler
statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
return statementHandler;
}
public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
//根据MappedStatement的类型创建一个实际使用的StatementHandler，默认为PREPARED
switch (ms.getStatementType()) {
case STATEMENT:
delegate = new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
break;
case PREPARED:
//chuan'jPreparedStatementHandler
delegate = new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
break;
case CALLABLE:
delegate = new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
break;
default:
throw new ExecutorException("Unknown statement type: " + ms.getStatementType());
}
}
public PreparedStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
//父类为BaseStatementHandler
super(executor, mappedStatement, parameter, rowBounds, resultHandler, boundSql);
}
protected BaseStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
this.configuration = mappedStatement.getConfiguration();
this.executor = executor;
this.mappedStatement = mappedStatement;
this.rowBounds = rowBounds;
this.typeHandlerRegistry = configuration.getTypeHandlerRegistry();
this.objectFactory = configuration.getObjectFactory();
if (boundSql == null) { // issue #435, get the key before calculating the statement
generateKeys(parameterObject);
boundSql = mappedStatement.getBoundSql(parameterObject);
}
this.boundSql = boundSql;
//创建参数处理器，会经过拦截器链的包装
this.parameterHandler = configuration.newParameterHandler(mappedStatement, parameterObject, boundSql);
//创建结果集处理器，会经过拦截器链的包装
this.resultSetHandler = configuration.newResultSetHandler(executor, mappedStatement, rowBounds, parameterHandler, resultHandler, boundSql);
}
stmt = prepareStatement(handler, ms.getStatementLog())：获取Statement（PreparedStatement）
private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
Statement stmt;
//获取连接（Transaction.getConnection -> DataSource.getConnection）
Connection connection = getConnection(statementLog);
//预编译sql,获取Statement（Connection.prepareStatement）
stmt = handler.prepare(connection, transaction.getTimeout());
//使用parameterHandler给预编译的sql设置参数
handler.parameterize(stmt);
return stmt;
}
handler.query(stmt, resultHandler):执行sql语言
@Override
public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
PreparedStatement ps = (PreparedStatement) statement;
//执行查询
ps.execute();
//使用resultSetHandler处理结果集，并返回
return resultSetHandler.handleResultSets(ps);
}
