136 lines
6.2 KiB
Markdown
Executable File
136 lines
6.2 KiB
Markdown
Executable File
- Mybatis初始化过程
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- 通过InputStream来获取配置文件
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- ClassLoaderWarpper中的getResourceAsStream可以根据配置的resoutce来获取到配置文件的输入六
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- 使用ClassLoader是因为类加载器可具有读取外部资源的能力
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- 
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- 读取到配置文件后传入SqlSessionFactoryBuilder，内部使用XMLConfigBuilder的parse方法读取配置并set到一个configuration变量中返回一个Configuration对象
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- 
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- 使用build方法创建一个DefaultSqlSessionFactory并返回
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- 在其中会创建一个SqlSession，其中会创建事务工厂之类的
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- 
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- 将mapper类传入session，通过session.getMapper方法在mapperRegistry获取到一个该mapper类的代理类MapperProxy
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- 执行时会执行该代理类的invoke方法
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- 
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- 触发mapperMethod的execute方法
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- ```java
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public Object execute(SqlSession sqlSession, Object[] args) {
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Object result;
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switch (command.getType()) {
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case *INSERT*: {
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Object param = method.convertArgsToSqlCommandParam(args);
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result = rowCountResult(sqlSession.insert(command.getName(), param));
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break;
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}
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case *UPDATE*: {
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Object param = method.convertArgsToSqlCommandParam(args);
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result = rowCountResult(sqlSession.update(command.getName(), param));
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break;
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}
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case *DELETE*: {
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Object param = method.convertArgsToSqlCommandParam(args);
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result = rowCountResult(sqlSession.delete(command.getName(), param));
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break;
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}
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case *SELECT*:
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if (method.returnsVoid() && method.hasResultHandler()) {
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executeWithResultHandler(sqlSession, args);
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result = null;
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} else if (method.returnsMany()) {
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result = executeForMany(sqlSession, args);
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} else if (method.returnsMap()) {
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result = executeForMap(sqlSession, args);
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} else if (method.returnsCursor()) {
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result = executeForCursor(sqlSession, args);
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} else {
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Object param = method.convertArgsToSqlCommandParam(args);
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result = sqlSession.selectOne(command.getName(), param);
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if (method.returnsOptional()
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&& (result == null || !method.getReturnType().equals(result.getClass()))) {
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result = Optional.*ofNullable*(result);
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}
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}
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break;
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case *FLUSH*:
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result = sqlSession.flushStatements();
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break;
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default:
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throw new BindingException("Unknown execution method for: " + command.getName());
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}
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if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
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throw new BindingException("Mapper method '" + command.getName()
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+ " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
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}
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return result;
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}
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```
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- 会根据不同的语句类型执行不同的execute方法，查询list会执行executeForMany方法
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- ```java
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private <E> Object executeForMany(SqlSession sqlSession, Object[] args) {
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List<E> result;
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Object param = method.convertArgsToSqlCommandParam(args);
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if (method.hasRowBounds()) {
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RowBounds rowBounds = method.extractRowBounds(args);
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result = sqlSession.selectList(command.getName(), param, rowBounds);
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} else {
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result = sqlSession.selectList(command.getName(), param);
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}
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*// issue #510 Collections & arrays support
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* if (!method.getReturnType().isAssignableFrom(result.getClass())) {
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if (method.getReturnType().isArray()) {
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return convertToArray(result);
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} else {
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return convertToDeclaredCollection(sqlSession.getConfiguration(), result);
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}
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}
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return result;
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}
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```
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- selectList获取MappedStatement，再执行executor.query方法
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- ```java
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@Override
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public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
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BoundSql boundSql = ms.getBoundSql(parameterObject);
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CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql);
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return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
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}
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```
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- BoundSql为去掉if，where标签的sql语句，Cachekey为缓存key
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- 查询时先从缓存获取，获取不到或list为null就执行delegate.query方法查询
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- 检查executor是否被关闭，是否清理缓存
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- 通过queryFromDatabase，先在缓存中放一个占位符，接着使用doQuery方法查询，然后把缓存中的占位符换成真正的结果
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- ```java
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private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
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List<E> list;
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localCache.putObject(key, *EXECUTION_PLACEHOLDER*);
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try {
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list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
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} finally {
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localCache.removeObject(key);
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}
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localCache.putObject(key, list);
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if (ms.getStatementType() == StatementType.*CALLABLE*) {
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localOutputParameterCache.putObject(key, parameter);
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}
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return list;
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}
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```
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- 执行doQuery方法，为BatchExecutor类的方法
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- ```java
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public <E> List<E> doQuery(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql)
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throws SQLException {
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Statement stmt = null;
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try {
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flushStatements();
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Configuration configuration = ms.getConfiguration();
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StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameterObject, rowBounds, resultHandler, boundSql);
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Connection connection = getConnection(ms.getStatementLog());
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stmt = handler.prepare(connection, transaction.getTimeout());
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handler.parameterize(stmt);
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return handler.query(stmt, resultHandler);
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} finally {
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closeStatement(stmt);
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}
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}
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```
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- 通过Statement执行静态语句获取结果
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- 执行的是PrepareStatementHandler.query方法，获取结果后交给ResultSetHandler处理，通过resultMap将值赋值给对象 |