开篇
这篇文章的目的是介绍Fescar的RM模块中的ExecuteTemplate的代码，ExecuteTemplate作为StatementProxy当中真正执行SQL操作的模块，在Proxy和Executor的串联中起到承上启下的作用。
调用链上按照DataSourceProxy->ConnectionProxy->StatementProxy->Executor的顺序进行。
ExecuteTemplate源码介绍
public class StatementProxy<T extends Statement> extends AbstractStatementProxy<T> {
@Override
public ResultSet executeQuery(String sql) throws SQLException {
this.targetSQL = sql;
return ExecuteTemplate.execute(this, new StatementCallback<ResultSet, T>() {
@Override
public ResultSet execute(Statement statement, Object... args)
throws SQLException {
return statement.executeQuery((String) args[0]);
}
}, sql);
}
@Override
public int executeUpdate(String sql) throws SQLException {
this.targetSQL = sql;
return ExecuteTemplate.execute(this, new StatementCallback<Integer, T>() {
@Override
public Integer execute(Statement statement, Object... args)
throws SQLException {
return statement.executeUpdate((String) args[0]);
}
}, sql);
}
}
说明：
- StatementProxy通过执行executeQuery和executeUpdate执行具体的SQL语句。
public class ExecuteTemplate {
public static <T, S extends Statement> T execute(StatementProxy<S> statementProxy,
StatementCallback<T, S> statementCallback,
Object... args) throws SQLException {
return execute(null, statementProxy, statementCallback, args);
}
public static <T, S extends Statement> T execute(SQLRecognizer sqlRecognizer,
StatementProxy<S> statementProxy,
StatementCallback<T, S> statementCallback,
Object... args) throws SQLException {
if (!RootContext.inGlobalTransaction()) {
// Just work as original statement
return statementCallback.execute(statementProxy.getTargetStatement(), args);
}
if (sqlRecognizer == null) {
sqlRecognizer = SQLVisitorFactory.get(
statementProxy.getTargetSQL(),
statementProxy.getConnectionProxy().getDbType());
}
Executor<T> executor = null;
if (sqlRecognizer == null) {
executor = new PlainExecutor<T, S>(statementProxy, statementCallback);
} else {
switch (sqlRecognizer.getSQLType()) {
case INSERT:
executor = new InsertExecutor<T, S>(statementProxy, statementCallback, sqlRecognizer);
break;
case UPDATE:
executor = new UpdateExecutor<T, S>(statementProxy, statementCallback, sqlRecognizer);
break;
case DELETE:
executor = new DeleteExecutor<T, S>(statementProxy, statementCallback, sqlRecognizer);
break;
case SELECT_FOR_UPDATE:
executor = new SelectForUpdateExecutor(statementProxy, statementCallback, sqlRecognizer);
break;
default:
executor = new PlainExecutor<T, S>(statementProxy, statementCallback);
break;
}
}
T rs = null;
try {
rs = executor.execute(args);
} catch (Throwable ex) {
if (ex instanceof SQLException) {
throw (SQLException) ex;
} else {
// Turn everything into SQLException
new SQLException(ex);
}
}
return rs;
}
}
说明：
- ExecuteTemplate内部根据SQL执行类型不同分为InsertExecutor、UpdateExecutor、DeleteExecutor、SelectForUpdateExecutor、PlainExecutor。
- InsertExecutor负责执行insert的SQL。
- UpdateExecutor负责执行update的SQL。
- DeleteExecutor负责执行delete的SQL。
- SelectForUpdateExecutor负责执行select for update操作的SQL。
期待
后续进一步分析不同的Executor的执行逻辑，很快就要接近RM的核心逻辑。
