Mybatis-plus 源码执行全流程解析

系统管理员 2023-10-02 23:39 13阅读 0赞

废话 少数流程开始：

1、业务入口：userMapper.insertBatch(entityList);

执行到代理类： $Proxy222 (com.sun.proxy) 开始走代理流程，然后到了代理类：

idea 执行流程取出栈信息：

![789bbcddea964f6ea6437d23135bef52.png][]

invoke:89, MybatisMapperProxy (com.baomidou.mybatisplus.core.override)

提前生成sqlSession ，地方如下：

2、代理类：public class MybatisMapperProxy<T> implements InvocationHandler, Serializable

// 当前代理类、方法名、保存的参数对象，可能多个
        @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 {//核心接口进入，带着生成的sqlSession
                    return cachedInvoker(method).invoke(proxy, method, args, sqlSession);
                }
            } catch (Throwable t) {
                throw ExceptionUtil.unwrapThrowable(t);
            }
        }

来到：

// private final Map<Method, MapperMethodInvoker> methodCache; 类似缓存操作
     private MapperMethodInvoker cachedInvoker(Method method) throws Throwable {
            try {// 集合的操作方法，通过接口回调返回数据
                return CollectionUtils.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 MybatisMapperMethod(mapperInterface, method, sqlSession.getConfiguration()));
                    }
                });
            } catch (RuntimeException re) {
                Throwable cause = re.getCause();
                throw cause == null ? re : cause;
            }
        }

进入新的invoke 方法：

@Override
            public Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable {
                //private final MybatisMapperMethod mapperMethod 方法名对象
                return mapperMethod.execute(sqlSession, args);//核心操作
            }

3、来到 public class MybatisMapperMethod 类：

// private final MapperMethod.MethodSignature method ;方法的类名
    public Object execute(SqlSession sqlSession, Object[] args) {
            Object result;
            switch (command.getType()) {//MapperMethod.SqlCommand command; 对象
                case INSERT: {//新增会走这里，点击进入，合成参数数据，进入
                    Object param = method.convertArgsToSqlCommandParam(args);
                    //通过方法名、参数，执行并返回执行结果，进入
                    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);
                        // TODO 这里下面改了
                        if (IPage.class.isAssignableFrom(method.getReturnType())) {
                            result = executeForIPage(sqlSession, args);
                            // TODO 这里上面改了
                        } else {
                            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;
        }

4、来到 public class MapperMethod 的内部类MethodSignature

//private final ParamNameResolver paramNameResolver; 参数分解器
       public Object convertArgsToSqlCommandParam(Object[] args) {
          return paramNameResolver.getNamedParams(args);//进入
        }

5、来到：public class ParamNameResolver

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;
        }
      }

最后返回：

![875d4d8fe9894ca79253f000786e542d.png][]

下面重点分析：

result = rowCountResult(sqlSession.insert(command.getName(), param));

点击 sqlSession.insert(command.getName(), param) 进入：三个实现类的其中一个

![9d5cf05f726c4414934eadb6886430bb.png][]

根据上游入口判断进入spring的类：

public class SqlSessionTemplate implements SqlSession, DisposableBean

6、来到 SqlSessionTemplate

//private final SqlSession sqlSessionProxy;方法的全路径、执行参数
      @Override
      public int insert(String statement, Object parameter) {
        return this.sqlSessionProxy.insert(statement, parameter);//进入
      }

三个实现类：

![361c43cf6cd842d593098710811e9f2a.png][] 来到子类 public class DefaultSqlSession implements SqlSession

7、DefaultSqlSession

@Override
      public int insert(String statement, Object parameter) {
        return update(statement, parameter);//进入执行
      }

来到：

//private final Executor executor;执行器接口
     //private final Configuration configuration; 配置类
      @Override
      public int update(String statement, Object parameter) {
        try {
          dirty = true;
          MappedStatement ms = configuration.getMappedStatement(statement);//创建声明，进入
          return executor.update(ms, wrapCollection(parameter));//正式执行
        } catch (Exception e) {
          throw ExceptionFactory.wrapException("Error updating database.  Cause: " + e, e);
        } finally {
          ErrorContext.instance().reset();//实例资源清除
        }
      }

点击configuration.getMappedStatement(statement) 进入

![2eb9066852f744929dd718c50181fc3b.png][]

来到 public class MybatisConfiguration extends Configuration 此类为mybatisplus的类，继承的mybatis的配置类Configuration 。

8、MybatisConfiguration 类

//此id就是mapper的全路径，在此服务中应该也是唯一的值
        @Override
        public MappedStatement getMappedStatement(String id) {
            return this.getMappedStatement(id, true);//正式获取声明
        }

来到：

//protected final Map<String, MappedStatement> mappedStatements 
        @Override
        public MappedStatement getMappedStatement(String id, boolean validateIncompleteStatements) {
            if (validateIncompleteStatements) {
                buildAllStatements();//上游传的true,进入
            }
            return mappedStatements.get(id);//在此处返回
        }

点击： buildAllStatements() 进入父类Configuration，组装的细节后面我们会详细分享

protected void buildAllStatements() {
        parsePendingResultMaps();
        if (!incompleteCacheRefs.isEmpty()) {
          synchronized (incompleteCacheRefs) {
            incompleteCacheRefs.removeIf(x -> x.resolveCacheRef() != null);
          }
        }
        if (!incompleteStatements.isEmpty()) {
          synchronized (incompleteStatements) {
            incompleteStatements.removeIf(x -> {
              x.parseStatementNode();
              return true;
            });
          }
        }
        if (!incompleteMethods.isEmpty()) {
          synchronized (incompleteMethods) {
            incompleteMethods.removeIf(x -> {
              x.resolve();
              return true;
            });
          }
        }
      }

返回后进入 executor.update(ms, wrapCollection(parameter));进入切面类

public class Plugin implements InvocationHandler

//切面方法
      @Override
      public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        try {
          Set<Method> methods = signatureMap.get(method.getDeclaringClass());
          if (methods != null && methods.contains(method)) {
            //private final Interceptor interceptor;拦截器接口
            return interceptor.intercept(new Invocation(target, method, args));//进入拦截器
          }
          return method.invoke(target, args);//进行执行业务
        } catch (Exception e) {
          throw ExceptionUtil.unwrapThrowable(e);
        }
      }

点击：![807ebfa2cfd942809ddff3b8c7f61cbf.png][]

来到：public class OptimisticLockerInterceptor implements Interceptor mybatis 中的类

@Override
        @SuppressWarnings({"unchecked", "rawtypes"})
        public Object intercept(Invocation invocation) throws Throwable {
            Object[] args = invocation.getArgs();
            MappedStatement ms = (MappedStatement) args[0];
            if (SqlCommandType.UPDATE != ms.getSqlCommandType()) {
                return invocation.proceed();
            }
            Object param = args[1];
            if (param instanceof Map) {
                Map map = (Map) param;
                //updateById(et), update(et, wrapper);
                Object et = map.getOrDefault(Constants.ENTITY, null);
                if (et != null) {
                    // entity
                    String methodId = ms.getId();
                    String methodName = methodId.substring(methodId.lastIndexOf(StringPool.DOT) + 1);
                    TableInfo tableInfo = TableInfoHelper.getTableInfo(et.getClass());
                    if (tableInfo == null || !tableInfo.isWithVersion()) {
                        return invocation.proceed();
                    }
                    TableFieldInfo fieldInfo = tableInfo.getVersionFieldInfo();
                    Field versionField = fieldInfo.getField();
                    // 旧的 version 值
                    Object originalVersionVal = versionField.get(et);
                    if (originalVersionVal == null) {
                        return invocation.proceed();
                    }
                    String versionColumn = fieldInfo.getColumn();
                    // 新的 version 值
                    Object updatedVersionVal = this.getUpdatedVersionVal(fieldInfo.getPropertyType(), originalVersionVal);
                    if (PARAM_UPDATE_METHOD_NAME.equals(methodName)) {
                        AbstractWrapper<?, ?, ?> aw = (AbstractWrapper<?, ?, ?>) map.getOrDefault(Constants.WRAPPER, null);
                        if (aw == null) {
                            UpdateWrapper<?> uw = new UpdateWrapper<>();
                            uw.eq(versionColumn, originalVersionVal);
                            map.put(Constants.WRAPPER, uw);
                        } else {
                            aw.apply(versionColumn + " = {0}", originalVersionVal);
                        }
                    } else {
                        map.put(Constants.MP_OPTLOCK_VERSION_ORIGINAL, originalVersionVal);
                    }
                    versionField.set(et, updatedVersionVal);
                    return invocation.proceed();
                }
            }
            return invocation.proceed();//点击进入
        }

来到：public class Invocation

public Object proceed() throws InvocationTargetException, IllegalAccessException {
      return method.invoke(target, args);//进入
    }

到了：public final class Method extends Executable

@CallerSensitive
        @ForceInline // to ensure Reflection.getCallerClass optimization
        @HotSpotIntrinsicCandidate
        public Object invoke(Object obj, Object... args)
            throws IllegalAccessException, IllegalArgumentException,
               InvocationTargetException
        {
            if (!override) {
                Class<?> caller = Reflection.getCallerClass();
                checkAccess(caller, clazz,
                            Modifier.isStatic(modifiers) ? null : obj.getClass(),
                            modifiers);
            }
            MethodAccessor ma = methodAccessor;             // read volatile
            if (ma == null) {
                ma = acquireMethodAccessor();
            }
            return ma.invoke(obj, args);//进入
        }

进入：

三个实现类

![6815af85e2fa4ae982f6ee13adbe6b87.png][]

9、来到 public class MybatisCachingExecutor implements Executor 实现类 mybatisplus包中

@Override
        public int update(MappedStatement ms, Object parameterObject) throws SQLException {
            flushCacheIfRequired(ms);//刷新清除缓存，下次查询此表，会到数据库查，点击
            // private final Executor delegate;执行器执行
            return delegate.update(ms, parameterObject);//核心执行,点击
        }

来到：

private void flushCacheIfRequired(MappedStatement ms) {
            Cache cache = ms.getCache();
            if (cache != null && ms.isFlushCacheRequired()) {
                tcm.clear(cache);//清除缓存
            }
        }

点击 delegate.update(ms, parameterObject);

10、到了 public abstract class BaseExecutor implements Executor

@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.");
        }
        clearLocalCache();//清除缓存
        return doUpdate(ms, parameter);//正式执行
      }

点击：

protected abstract int doUpdate(MappedStatement ms, Object parameter) throws SQLException;

抽象方法的重写：有mybatis和plus的两组实现

![cdaf0fe96fd043c0883e0d66a2b96864.png][]10、 到：public class MybatisSimpleExecutor extends AbstractBaseExecutor

@Override
        public int doUpdate(MappedStatement ms, Object parameter) throws SQLException {
            Statement stmt = null;
            try {
                Configuration configuration = ms.getConfiguration();
                StatementHandler handler = configuration.newStatementHandler(this, ms, parameter, RowBounds.DEFAULT, null, null);//生成执行的声明，里面很复杂，后期我们很专题讲解
                stmt = prepareStatement(handler, ms.getStatementLog(), false);//拿数据源重点，进入
                return stmt == null ? 0 : handler.update(stmt);//正式执行，点击
            } finally {
                closeStatement(stmt);//关闭声明
            }
        }

点击 prepareStatement(handler, ms.getStatementLog(), false);

private Statement prepareStatement(StatementHandler handler, Log statementLog, boolean isCursor) throws SQLException {
            Statement stmt;
            Connection connection = getConnection(statementLog);//取数据源，进入
            stmt = handler.prepare(connection, transaction.getTimeout());封装数据源到声明里
            //游标不支持返回null.
            if (stmt == null && !isCursor) {
                return null;
            } else {
                handler.parameterize(stmt);
                return stmt;
            }
        }

11、到了父类 public abstract class BaseExecutor implements Executor

protected Connection getConnection(Log statementLog) throws SQLException {
        // protected Transaction transaction;
        Connection connection = transaction.getConnection();//获取数据源,进入
        if (statementLog.isDebugEnabled()) {
          return ConnectionLogger.newInstance(connection, statementLog, queryStack);
        } else {
          return connection;
        }
      }

点击发现常用的三种实现：

![776c50dea50c4cc2b6bde98f06970ae5.png][]

显然 进入 mybatis-spring 包里的SpringManagedTransaction

10、来到 public class SpringManagedTransaction implements Transaction 类

@Override
      public Connection getConnection() throws SQLException {
        if (this.connection == null) {
          openConnection();//获取连接，进入
        }
        return this.connection;
      }

点击 openConnection()

private void openConnection() throws SQLException {
        //通过spring的工具类DataSourceUtils 获取 数据库连接connection（JDK包里的），进入
        this.connection = DataSourceUtils.getConnection(this.dataSource);
        this.autoCommit = this.connection.getAutoCommit();//自动提交的获取
        //是否连接、事务的判断
        this.isConnectionTransactional = DataSourceUtils.isConnectionTransactional(this.connection, this.dataSource);
    
        LOGGER.debug(() -> "JDBC Connection [" + this.connection + "] will"
            + (this.isConnectionTransactional ? " " : " not ") + "be managed by Spring");
      }

来到：

public static Connection getConnection(DataSource dataSource) throws CannotGetJdbcConnectionException {
    		try {
    			return doGetConnection(dataSource);//点击
    		}
    		catch (SQLException ex) {
    			throw new CannotGetJdbcConnectionException("Failed to obtain JDBC Connection", ex);
    		}
    		catch (IllegalStateException ex) {
    			throw new CannotGetJdbcConnectionException("Failed to obtain JDBC Connection: " + ex.getMessage());
    		}
    	}

点击：

public static Connection doGetConnection(DataSource dataSource) throws SQLException {
    		Assert.notNull(dataSource, "No DataSource specified");
    
    		ConnectionHolder conHolder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource);
    		if (conHolder != null && (conHolder.hasConnection() || conHolder.isSynchronizedWithTransaction())) {
    			conHolder.requested();
    			if (!conHolder.hasConnection()) {
    				logger.debug("Fetching resumed JDBC Connection from DataSource");
    				conHolder.setConnection(fetchConnection(dataSource));
    			}
    			return conHolder.getConnection();
    		}
    		// Else we either got no holder or an empty thread-bound holder here.
    
    		logger.debug("Fetching JDBC Connection from DataSource");
    		Connection con = fetchConnection(dataSource);//重点进入
    
    		if (TransactionSynchronizationManager.isSynchronizationActive()) {
    			try {
    				// Use same Connection for further JDBC actions within the transaction.
    				// Thread-bound object will get removed by synchronization at transaction completion.
    				ConnectionHolder holderToUse = conHolder;
    				if (holderToUse == null) {
    					holderToUse = new ConnectionHolder(con);
    				}
    				else {
    					holderToUse.setConnection(con);
    				}
    				holderToUse.requested();
    				TransactionSynchronizationManager.registerSynchronization(
    						new ConnectionSynchronization(holderToUse, dataSource));
    				holderToUse.setSynchronizedWithTransaction(true);
    				if (holderToUse != conHolder) {
    					TransactionSynchronizationManager.bindResource(dataSource, holderToUse);
    				}
    			}
    			catch (RuntimeException ex) {
    				// Unexpected exception from external delegation call -> close Connection and rethrow.
    				releaseConnection(con, dataSource);
    				throw ex;
    			}
    		}
    
    		return con;
    	}

来到：

private static Connection fetchConnection(DataSource dataSource) throws SQLException {
    		Connection con = dataSource.getConnection();//点击进入，dataSource 的实现类
    		if (con == null) {
    			throw new IllegalStateException("DataSource returned null from getConnection(): " + dataSource);
    		}
    		return con;
    	}

点击：dataSource.getConnection()发现好的实现类，应该进入哪一个啊？？

![b01ec0ed26954affb5f9bde85a5c676d.png][]

根据业务判断：进入NandaoDataSource

public class NandaoDataSource  extends AbstractTenantDataSource implements DataSource, NandaoDataSourceMXBean, MBeanRegistration, AutoCloseable{

@Override
        public Connection getConnection() throws SQLException {
            if (provider == null) {
                throw new Exception("provider is null");
            }
            return getConnection(provider.getUserId());//业务封装回去自定义数据源
        }

进入

public Connection getConnection(String userId) throws SQLException {
    
            for (int retry = 1; retry <= retryTimes; retry++) {
                UserDbInfo dbInfo = userDbInfoInfoService.getDatabaseInfo(userId);
                
                    return getDataSource(dbInfo).getConnection();
               }
        }

这是获取数据源的流程，分析到此，下篇我们分析真正执行数据库的流程 handler.update(stmt);，敬请期待！

[789bbcddea964f6ea6437d23135bef52.png]: https://img-blog.csdnimg.cn/789bbcddea964f6ea6437d23135bef52.png
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[2eb9066852f744929dd718c50181fc3b.png]: https://img-blog.csdnimg.cn/2eb9066852f744929dd718c50181fc3b.png
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[cdaf0fe96fd043c0883e0d66a2b96864.png]: https://img-blog.csdnimg.cn/cdaf0fe96fd043c0883e0d66a2b96864.png
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[b01ec0ed26954affb5f9bde85a5c676d.png]: https://img-blog.csdnimg.cn/b01ec0ed26954affb5f9bde85a5c676d.png