Mybatis的署理对象MapperProxy的CURD

藏宝库编辑 · 2024-9-7 21:35:20

上篇-原生mybatis流程
因Mapper是interface，不能实例化对象，以是必须使用动态署理（使用JDK动态署理）创建署理对象MapperProxy，又因Mapper是接口，没有具体的方法体，以是MapperProxy的invoke方法中自行编写方法逻辑，下面先容CURD的实行过程。
public class MapperProxy<T> implements InvocationHandler, Serializable {略@Override  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { try {    if (Object.class.equals(method.getDeclaringClass())) {       return method.invoke(this, args);    } else {       return cachedInvoker(method).invoke(proxy, method, args, sqlSession);    } } catch (Throwable t) {    throw ExceptionUtil.unwrapThrowable(t); }  }  private MapperMethodInvoker cachedInvoker(Method method) throws Throwable { try {    return MapUtil.computeIfAbsent(methodCache, method, m -> {       if (m.isDefault()) {       try {          if (privateLookupInMethod == null) {             return new DefaultMethodInvoker(getMethodHandleJava8(method));          } else {             return new DefaultMethodInvoker(getMethodHandleJava9(method));          }       } catch (IllegalAccessException | InstantiationException | InvocationTargetException             | NoSuchMethodException e) {          throw new RuntimeException(e);       }       } else {       return new PlainMethodInvoker(new MapperMethod(mapperInterface, method, sqlSession.getConfiguration()));       }    }); } catch (RuntimeException re) {    Throwable cause = re.getCause();    throw cause == null ? re : cause; }  }}###调用MapperBean中的非default方法  private static class PlainMethodInvoker implements MapperMethodInvoker { private final MapperMethod mapperMethod; public PlainMethodInvoker(MapperMethod mapperMethod) {    super();    this.mapperMethod = mapperMethod; } @Override public Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable {    return mapperMethod.execute(sqlSession, args); }  }可见mapperMethod来实行execute，携带sqlSession和参数（默认的statement是prepareStatement）

mapperMethod类中有2个属性，分别是SqlCommand、MethodSignature,均是MapperMethod的内部类。
public class MapperMethod {  private final SqlCommand command;  private final MethodSignature method;  public static class SqlCommand { 类全路径名+方法名：com.orion.mapper.TAccountMapper.selectByPrimaryKey private final String name; 罗列，CURD那几种，如SELECT private final SqlCommandType type;  } public static class MethodSignature { private final boolean returnsMany; private final boolean returnsMap; private final boolean returnsVoid; private final boolean returnsCursor; private final boolean returnsOptional; 返回范例 private final Class<?> returnType; private final String mapKey; private final Integer resultHandlerIndex; private final Integer rowBoundsIndex; 参数 private final ParamNameResolver paramNameResolver;  }  }SELECT

debug下去终极实行execute之类的方法，而实行的execute方法是sqlSession，注意sqlSession是携带configuration的，configuration内里有mappedStatement（全部方法聚集），末了根据SqlCommand中的name作为id从mappedStatement中获取相应的MappedStatement对象。
DefaultSqlSession:  private <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) { try {    MappedStatement ms = configuration.getMappedStatement(statement);    return executor.query(ms, wrapCollection(parameter), rowBounds, handler); } catch (Exception e) {    throw ExceptionFactory.wrapException("Error querying database.  Cause: " + e, e); } finally {    ErrorContext.instance().reset(); }  }CachingExecutor:  @Override  public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException { BoundSql boundSql = ms.getBoundSql(parameterObject); CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql); return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);  }MappedStatement：  public BoundSql getBoundSql(Object parameterObject) { BoundSql boundSql = sqlSource.getBoundSql(parameterObject); List<

arameterMapping> parameterMappings = boundSql.getParameterMappings(); if (parameterMappings == null || parameterMappings.isEmpty()) { boundSql = new BoundSql(configuration, boundSql.getSql(), parameterMap.getParameterMappings(), parameterObject); } // check for nested result maps in parameter mappings (issue #30) for (ParameterMapping pm : boundSql.getParameterMappings()) { String rmId = pm.getResultMapId(); if (rmId != null) { ResultMap rm = configuration.getResultMap(rmId); if (rm != null) { hasNestedResultMaps |= rm.hasNestedResultMaps(); } } } return boundSql; } public BoundSql getBoundSql(Object parameterObject) { BoundSql boundSql = sqlSource.getBoundSql(parameterObject); List<

arameterMapping> parameterMappings = boundSql.getParameterMappings(); if (parameterMappings == null || parameterMappings.isEmpty()) { boundSql = new BoundSql(configuration, boundSql.getSql(), parameterMap.getParameterMappings(), parameterObject); }boundSql内下属性，具有sql以及参数mapping

终极去到BaseExecutor，实行query方法,第一次没有缓存，走queryFromDatabase方法，注意一级缓存是session级别，二级缓存才是最大范围全局的。

@SuppressWarnings("unchecked") @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) { handleLocallyCachedOutputParameters(ms, key, parameter, boundSql); } else { 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; }查询数据库，将Cachekey加入本地内存 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 { 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: @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); ！！！参数mapping，stmt是一个proxy stmt = prepareStatement(handler, ms.getStatementLog()); return handler.query(stmt, resultHandler); } finally { closeStatement(stmt); } } private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException { Statement stmt; Connection connection = getConnection(statementLog); stmt = handler.prepare(connection, transaction.getTimeout()); //参数按照index嵌入，无参数的也是prepareStatementHandler ，只是parameterize里不会循环而已 handler.parameterize(stmt); return stmt; }ConnectionLogger：@Override public Object invoke(Object proxy, Method method, Object[] params) throws Throwable { try { if (Object.class.equals(method.getDeclaringClass())) { return method.invoke(this, params); } if ("prepareStatement".equals(method.getName()) || "prepareCall".equals(method.getName())) { if (isDebugEnabled()) { debug(" Preparing: " + removeExtraWhitespace((String) params[0]), true); } PreparedStatement stmt = (PreparedStatement) method.invoke(connection, params); stmt = PreparedStatementLogger.newInstance(stmt, statementLog, queryStack); return stmt; } else if ("createStatement".equals(method.getName())) { Statement stmt = (Statement) method.invoke(connection, params); stmt = StatementLogger.newInstance(stmt, statementLog, queryStack); return stmt; } else { return method.invoke(connection, params); } } catch (Throwable t) { throw ExceptionUtil.unwrapThrowable(t); } }末了结果resultMap匹配映射，返回结果集，完成过程

PreparedStatementHandler: @Override public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException { PreparedStatement ps = (PreparedStatement) statement; ps.execute(); return resultSetHandler.handleResultSets(ps); }

剩下的增加、删除、修改

MapperMethod:rowCountResult就是返回影响行数 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 { 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; }它们末了都是实行DefaultSqlSession中的update方法：
DefaultSqlSession: @Override public int update(String statement, Object parameter) { try { dirty = true; MappedStatement ms = configuration.getMappedStatement(statement); return executor.update(ms, wrapCollection(parameter)); } catch (Exception e) { throw ExceptionFactory.wrapException("Error updating database. Cause: " + e, e); } finally { ErrorContext.instance().reset(); } }SimpleExecutor @Override public int update(MappedStatement ms, Object parameter) throws SQLException { ErrorContext.instance().resource(ms.getResource()).activity("executing an update").object(ms.getId()); if (closed) { throw new ExecutorException("Executor was closed."); } update就是要清除LocalCache clearLocalCache(); return doUpdate(ms, parameter); } @Override public int doUpdate(MappedStatement ms, Object parameter) throws SQLException {主体代码和select差不多 Statement stmt = null; try { Configuration configuration = ms.getConfiguration(); StatementHandler handler = configuration.newStatementHandler(this, ms, parameter, RowBounds.DEFAULT, null, null); stmt = prepareStatement(handler, ms.getStatementLog()); return handler.update(stmt); } finally { closeStatement(stmt); } } PreparedStatementHandler ： @Override public int update(Statement statement) throws SQLException { PreparedStatement ps = (PreparedStatement) statement; ps.execute(); int rows = ps.getUpdateCount(); Object parameterObject = boundSql.getParameterObject(); KeyGenerator keyGenerator = mappedStatement.getKeyGenerator(); keyGenerator.processAfter(executor, mappedStatement, ps, parameterObject); return rows; }终极得到影响行数，竣事。

Mybatis的署理对象MapperProxy的CURD

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