Mybatis DyanmicSqlSourcce

  • Author: HuiFer

  • 源码阅读工程: SourceHot-Mybatis

  • org.apache.ibatis.scripting.xmltags.DynamicSqlSource

  • org.apache.ibatis.scripting.xmltags.DynamicContext.DynamicContext
  1.     <select id="list" resultType="com.huifer.mybatis.entity.HsSell">
  2.         select * from hs_sell
  3.         <trim prefix="WHERE" prefixOverrides="AND |OR">
  4.             <if test="ID != null">
  5.                 and ID = #{ID,jdbcType=INTEGER}
  6.             </if>
  8.         </trim>
  9.     </select>

image-20191219151247240

image-20191219151408597

  1. public class MixedSqlNode implements SqlNode {
  2.     private final List<SqlNode> contents;
  4.     public MixedSqlNode(List<SqlNode> contents) {
  5.         this.contents = contents;
  6.     }
  8.     @Override
  9.     public boolean apply(DynamicContext context) {
  10.         // 调用 salNode 对象本身的 apply 方法解析 sql
  11.         contents.forEach(node -> node.apply(context));
  12.         return true;
  13.     }
  14. }

  • 根据 mapper.xml 文件中的代码流程 需要走

    org.apache.ibatis.scripting.xmltags.StaticTextSqlNode#apply

    org.apache.ibatis.scripting.xmltags.TrimSqlNode#apply

    org.apache.ibatis.scripting.xmltags.IfSqlNode#apply

image-20191219152254274

  1. /**
  2.  * @author Clinton Begin
  3.  */
  4. public class StaticTextSqlNode implements SqlNode {
  5.     private final String text;
  7.     public StaticTextSqlNode(String text) {
  8.         this.text = text;
  9.     }
  11.     /**
  12.      * 静态文本apply 方法
  13.      * @param context
  14.      * @return
  15.      */
  16.     @Override
  17.     public boolean apply(DynamicContext context) {
  18.         context.appendSql(text);
  19.         return true;
  20.     }
  22. }

  • org.apache.ibatis.scripting.xmltags.DynamicContext#appendSql

    1.   public void appendSql(String sql) {
    2.       sqlBuilder.add(sql);
    3.   }

  • 解析trim标签

image-20191219152502960

  • 在解析trim的时候会往下解析下级标签

    1.     @Override
    2.     public boolean apply(DynamicContext context) {
    3.         FilteredDynamicContext filteredDynamicContext = new FilteredDynamicContext(context);
    4.        // 解析下级标签的入口
    5.         boolean result = contents.apply(filteredDynamicContext);
    6.         filteredDynamicContext.applyAll();
    7.         return result;
    8.     }

image-20191219152655746

  1.     @Override
  2.     public boolean apply(DynamicContext context) {
  3.         if (evaluator.evaluateBoolean(test, context.getBindings())) {
  4.             contents.apply(context);
  5.             return true;
  6.         }
  7.         return false;
  8.     }
  • evaluator.evaluateBoolean(test, context.getBindings())方法
  1.     /**
  2.      * @param expression      判断语句,ID != null
  3.      * @param parameterObject 参数列表
  4.      * @return
  5.      */
  6.     public boolean evaluateBoolean(String expression, Object parameterObject) {
  7.         Object value = OgnlCache.getValue(expression, parameterObject);
  8.         if (value instanceof Boolean) {
  9.             return (Boolean) value;
  10.         }
  11.         if (value instanceof Number) {
  12.             return new BigDecimal(String.valueOf(value)).compareTo(BigDecimal.ZERO) != 0;
  13.         }
  14.         return value != null;
  15.     }
  1.     /**
  2.      * 取值
  3.      * @param expression  判断语句,ID=NULL
  4.      * @param root 参数列表
  5.      * @return
  6.      */
  7.     public static Object getValue(String expression, Object root) {
  8.         try {
  9.             Map context = Ognl.createDefaultContext(root, MEMBER_ACCESS, CLASS_RESOLVER, null);
  10.             // 判断是否存在 expression 的判断内容 (判断ID是否存在)
  11.             return Ognl.getValue(parseExpression(expression), context, root);
  12.         } catch (OgnlException e) {
  13.             throw new BuilderException("Error evaluating expression '" + expression + "'. Cause: " + e, e);
  14.         }
  15.     }

image-20191219153341466

存在返回true

执行完成就得到了一个 sql

image-20191219153553127

继续执行org.apache.ibatis.scripting.xmltags.DynamicSqlSource#getBoundSql方法

image-20191219155129772

  • 发送 sqlorg.apache.ibatis.executor.SimpleExecutor#doQuery

  • 调用链路如下

  • org.apache.ibatis.executor.CachingExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler)

    • org.apache.ibatis.executor.CachingExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql)

    • org.apache.ibatis.executor.Executor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql)

    • org.apache.ibatis.executor.BaseExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql)

      1.     @SuppressWarnings("unchecked")
      2.     @Override
      3.     public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
      4.         ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
      5.         if (closed) {
      6.             // 判断当前是否关闭
      7.             throw new ExecutorException("Executor was closed.");
      8.         }
      9.         if (queryStack == 0 && ms.isFlushCacheRequired()) {
      10.             // 查询堆栈==0 和 是否需要刷新缓存
      11.             // 清理本地缓存
      12.             clearLocalCache();
      13.         }
      14.         List<E> list;
      15.         try {
      16. //            堆栈+1,防止重新清理缓存
      17.             queryStack++;
      18.             // 通过 缓存key 在本地缓存中获取
      19.             list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
      20.             if (list != null) {
      21.                 // 通过缓存 key 查到后处理  localOutputParameterCache
      22.                 handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
      23.             } else {
      24.                 // 没有查询到从数据库查询
      25.                 list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
      26.             }
      27.         } finally {
      28.             // 堆栈-1
      29.             queryStack--;
      30.         }
      31.         if (queryStack == 0) {
      32.             for (DeferredLoad deferredLoad : deferredLoads) {
      33.                 deferredLoad.load();
      34.             }
      35.             // 清空线程安全队列(延迟队列)
      36.             // issue #601
      37.             deferredLoads.clear();
      38.             if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
      39.                 // STATEMENT 清空本地缓存
      40.                 // issue #482
      41.                 clearLocalCache();
      42.             }
      43.         }
      44.         return list;
      45.     }

      • org.apache.ibatis.executor.BaseExecutor#queryFromDatabase

        1.     private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
        2.         List<E> list;
        3.         localCache.putObject(key, EXECUTION_PLACEHOLDER);
        4.         try {
        5.             list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
        6.         } finally {
        7.             localCache.removeObject(key);
        8.         }
        9.         localCache.putObject(key, list);
        10.         if (ms.getStatementType() == StatementType.CALLABLE) {
        11.             localOutputParameterCache.putObject(key, parameter);
        12.         }
        13.         return list;
        14.     }
        • org.apache.ibatis.executor.BaseExecutor#doQuery
        • org.apache.ibatis.executor.SimpleExecutor#doQuery

image-20191219160832704

  1.     private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
  2.         Statement stmt;
  3.         // 数据库连接
  4.         Connection connection = getConnection(statementLog);
  5.         // stms 创建
  6.         // org.apache.ibatis.executor.statement.BaseStatementHandler.prepare
  7.         stmt = handler.prepare(connection, transaction.getTimeout());
  8.         // 参数放入
  9.         handler.parameterize(stmt);
  10.         return stmt;
  11.     }

image-20191219160908212

  • org.apache.ibatis.executor.statement.BaseStatementHandler#prepare
    • org.apache.ibatis.executor.statement.PreparedStatementHandler#instantiateStatement
  1.     @Override
  2.     public Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException {
  3.         ErrorContext.instance().sql(boundSql.getSql());
  4.         Statement statement = null;
  5.         try {
  6.             statement = instantiateStatement(connection);
  7.             setStatementTimeout(statement, transactionTimeout);
  8.             setFetchSize(statement);
  9.             return statement;
  10.         } catch (SQLException e) {
  11.             closeStatement(statement);
  12.             throw e;
  13.         } catch (Exception e) {
  14.             closeStatement(statement);
  15.             throw new ExecutorException("Error preparing statement.  Cause: " + e, e);
  16.         }
  17.     }
  1.     @Override
  2.     protected Statement instantiateStatement(Connection connection) throws SQLException {
  3.         String sql = boundSql.getSql();
  4.         if (mappedStatement.getKeyGenerator() instanceof Jdbc3KeyGenerator) {
  5.             String[] keyColumnNames = mappedStatement.getKeyColumns();
  6.             if (keyColumnNames == null) {
  7.                 return connection.prepareStatement(sql, PreparedStatement.RETURN_GENERATED_KEYS);
  8.             } else {
  9.                 return connection.prepareStatement(sql, keyColumnNames);
  10.             }
  11.         } else if (mappedStatement.getResultSetType() == ResultSetType.DEFAULT) {
  12.             return connection.prepareStatement(sql);
  13.         } else {
  14.             return connection.prepareStatement(sql, mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);
  15.         }
  16.     }

  • 这个方法都去了java.sql.Connection#prepareStatement(java.lang.String, java.lang.String[])

  • 接下来需要考虑的问题是如何将?换成我们的参数2

    image-20191219161555793

  • org.apache.ibatis.executor.statement.StatementHandler#parameterize

    • org.apache.ibatis.executor.statement.RoutingStatementHandler#parameterize
      • org.apache.ibatis.executor.statement.StatementHandler#parameterize
        • org.apache.ibatis.executor.statement.PreparedStatementHandler#parameterize
          • org.apache.ibatis.executor.parameter.ParameterHandler
            • org.apache.ibatis.scripting.defaults.DefaultParameterHandler#setParameters

image-20191219162258040

这样就拿到了value的值

image-20191219162506920

准备工作就绪了发送就可以了

doQuery的工作完成了继续往下走

  1.     @Override
  2.     public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
  3.         Statement stmt = null;
  4.         try {
  5.             Configuration configuration = ms.getConfiguration();
  6.             StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
  7.             stmt = prepareStatement(handler, ms.getStatementLog());
  8.             return handler.query(stmt, resultHandler);
  9.         } finally {
  10.             closeStatement(stmt);
  11.         }
  12.     }
  • org.apache.ibatis.executor.statement.RoutingStatementHandler#query
    • org.apache.ibatis.executor.statement.PreparedStatementHandler#query
      • org.apache.ibatis.executor.resultset.ResultSetHandler#handleResultSets
      • org.apache.ibatis.executor.resultset.DefaultResultSetHandler#handleResultSets

image-20191219163628214

image-20191219163640968

image-20191219163957488

处理后结果如上

  1.     /**
  2.      * 处理查询结果
  3.      * @param stmt
  4.      * @return
  5.      * @throws SQLException
  6.      */
  7.     @Override
  8.     public List<Object> handleResultSets(Statement stmt) throws SQLException {
  9.         ErrorContext.instance().activity("handling results").object(mappedStatement.getId());
  11.         final List<Object> multipleResults = new ArrayList<>();
  13.         int resultSetCount = 0;
  14.         ResultSetWrapper rsw = getFirstResultSet(stmt);
  16.         List<ResultMap> resultMaps = mappedStatement.getResultMaps();
  17.         int resultMapCount = resultMaps.size();
  18.         validateResultMapsCount(rsw, resultMapCount);
  19.         while (rsw != null && resultMapCount > resultSetCount) {
  20.             ResultMap resultMap = resultMaps.get(resultSetCount);
  21.             handleResultSet(rsw, resultMap, multipleResults, null);
  22.             rsw = getNextResultSet(stmt);
  23.             cleanUpAfterHandlingResultSet();
  24.             resultSetCount++;
  25.         }
  27.         String[] resultSets = mappedStatement.getResultSets();
  28.         if (resultSets != null) {
  29.             while (rsw != null && resultSetCount < resultSets.length) {
  30.                 ResultMapping parentMapping = nextResultMaps.get(resultSets[resultSetCount]);
  31.                 if (parentMapping != null) {
  32.                     String nestedResultMapId = parentMapping.getNestedResultMapId();
  33.                     ResultMap resultMap = configuration.getResultMap(nestedResultMapId);
  34.                     handleResultSet(rsw, resultMap, null, parentMapping);
  35.                 }
  36.                 rsw = getNextResultSet(stmt);
  37.                 cleanUpAfterHandlingResultSet();
  38.                 resultSetCount++;
  39.             }
  40.         }
  42.         // 查询结果
  43.         return collapseSingleResultList(multipleResults);
  44.     }