对BatchExecutor进行中文注释

src/main/java/org/apache/ibatis/executor/BatchExecutor.java

@@ -35,74 +35,92 @@
 import org.apache.ibatis.transaction.Transaction;
 
 /**
- * @author Jeff Butler 
+ * @author Jeff Butler
  */
 public class BatchExecutor extends BaseExecutor {
 
   public static final int BATCH_UPDATE_RETURN_VALUE = Integer.MIN_VALUE + 1002;
 
+  //JDBC Statement接口:其实现类有PreparedStatement,PreparedStatement
   private final List<Statement> statementList = new ArrayList<Statement>();
+  //BatchResult主体是封装好的sql，这儿声明一个List主要是为了sql的复用
   private final List<BatchResult> batchResultList = new ArrayList<BatchResult>();
+  //executor当前的sql
   private String currentSql;
   private MappedStatement currentStatement;
 
+  //BatchExecutor也支持事务
   public BatchExecutor(Configuration configuration, Transaction transaction) {
     super(configuration, transaction);
   }
 
+  //为父类BaseExecutor中的doUpdate()方法的批量实现
   @Override
   public int doUpdate(MappedStatement ms, Object parameterObject) throws SQLException {
     final Configuration configuration = ms.getConfiguration();
     final StatementHandler handler = configuration.newStatementHandler(this, ms, parameterObject, RowBounds.DEFAULT, null, null);
     final BoundSql boundSql = handler.getBoundSql();
     final String sql = boundSql.getSql();
     final Statement stmt;
+    //获取当前sql对应的Statement
     if (sql.equals(currentSql) && ms.equals(currentStatement)) {
       int last = statementList.size() - 1;
       stmt = statementList.get(last);
       BatchResult batchResult = batchResultList.get(last);
       batchResult.addParameterObject(parameterObject);
     } else {
+      //如果没有当前sql对应的Statement,创建一个Statement并添加到batchResultList,方便下次复用
       Connection connection = getConnection(ms.getStatementLog());
       stmt = handler.prepare(connection);
       currentSql = sql;
       currentStatement = ms;
       statementList.add(stmt);
       batchResultList.add(new BatchResult(ms, sql, parameterObject));
     }
+    //给每个Statement设置参数
     handler.parameterize(stmt);
+    //调用Statement.batch()方法,批量更新
     handler.batch(stmt);
     return BATCH_UPDATE_RETURN_VALUE;
   }
 
+  //查询方法
   @Override
   public <E> List<E> doQuery(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql)
-      throws SQLException {
+          throws SQLException {
     Statement stmt = null;
     try {
+      //调用父类BaseExcutor的flushStatements()的方法执行BatchExecutor中doFlushStatements()方法
       flushStatements();
       Configuration configuration = ms.getConfiguration();
       StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameterObject, rowBounds, resultHandler, boundSql);
       Connection connection = getConnection(ms.getStatementLog());
       stmt = handler.prepare(connection);
+      //设置参数
       handler.parameterize(stmt);
+      //查询方法，并将查询到的结果交给resultHandler封装
       return handler.<E>query(stmt, resultHandler);
     } finally {
       closeStatement(stmt);
     }
   }
 
+  //实现父类BaseExcutor的静态方法
   @Override
   public List<BatchResult> doFlushStatements(boolean isRollback) throws SQLException {
     try {
       List<BatchResult> results = new ArrayList<BatchResult>();
       if (isRollback) {
+        //如果调用了父类BaseExecutor中回滚方法,会清空要执行的sql语句
         return Collections.emptyList();
       }
       for (int i = 0, n = statementList.size(); i < n; i++) {
         Statement stmt = statementList.get(i);
         BatchResult batchResult = batchResultList.get(i);
         try {
+          //对多个Statement的查询结果进行拦截,并设置返回的主键
+          //注:BatchExecutor的doQuery()不会执行此逻辑 查询时不存在sql语句复用 此时statementList为空
+          //反而是对doUpdate()方法进行了拦截,如果是对数据库进行批量添加,这里能够往bean中自动注入主键
           batchResult.setUpdateCounts(stmt.executeBatch());
           MappedStatement ms = batchResult.getMappedStatement();
           List<Object> parameterObjects = batchResult.getParameterObjects();
@@ -118,14 +136,14 @@ public List<BatchResult> doFlushStatements(boolean isRollback) throws SQLExcepti
         } catch (BatchUpdateException e) {
           StringBuilder message = new StringBuilder();
           message.append(batchResult.getMappedStatement().getId())
-              .append(" (batch index #")
-              .append(i + 1)
-              .append(")")
-              .append(" failed.");
+                  .append(" (batch index #")
+                  .append(i + 1)
+                  .append(")")
+                  .append(" failed.");
           if (i > 0) {
             message.append(" ")
-                .append(i)
-                .append(" prior sub executor(s) completed successfully, but will be rolled back.");
+                    .append(i)
+                    .append(" prior sub executor(s) completed successfully, but will be rolled back.");
           }
           throw new BatchExecutorException(message.toString(), e, results, batchResult);
         }