#952; Better error message or default connection manager

Author: babyfish-ct

project/jimmer-sql/src/main/java/org/babyfish/jimmer/sql/JSqlClientImpl.java

@@ -1618,13 +1618,13 @@ public Builder addExceptionTranslator(ExceptionTranslator<?> translator) {
 
         @Override
         public JSqlClient.Builder setExplicitBatchEnabled(boolean enabled) {
-            explicitBatchEnabled = true;
+            explicitBatchEnabled = enabled;
             return this;
         }
 
         @Override
         public JSqlClient.Builder setDumbBatchAcceptable(boolean acceptable) {
-            dumbBatchAcceptable = true;
+            dumbBatchAcceptable = acceptable;
             return this;
         }
 

project/jimmer-sql/src/main/java/org/babyfish/jimmer/sql/runtime/ConnectionManager.java

@@ -22,7 +22,17 @@ default <R> R execute(Function<Connection, R> block) {
     ConnectionManager EXTERNAL_ONLY = new ConnectionManager() {
         @Override
         public <R> R execute(@Nullable Connection con, Function<Connection, R> block) {
-            Objects.requireNonNull(con, "External connection cannot be null");
+            if (con == null) {
+                throw new IllegalArgumentException(
+                        "The connection manager is not specified " +
+                                "so \"ConnectionManager.EXTERNAL_ONLY\" " +
+                                "which does not support no explicit JDBC " +
+                                "connection execution is used as default. " +
+                                "There are 2 choices: " +
+                                "1. Specify the connection when execute statement/command" +
+                                "2. Specify the connection manager"
+                );
+            }
             return block.apply(con);
         }
     };

project/jimmer-sql/src/test/java/org/babyfish/jimmer/sql/mutation/IdentityTest.java

@@ -127,7 +127,10 @@ public void testInsertMySql() {
         NativeDatabases.assumeNativeDatabase();
         resetIdentity(NativeDatabases.MYSQL_DATA_SOURCE);
 
-        JSqlClient sqlClient = getSqlClient(it -> it.setDialect(new MySqlDialect()));
+        JSqlClient sqlClient = getSqlClient(it ->
+                it.setDialect(new MySqlDialect())
+                        .setExplicitBatchEnabled(true)
+        );
         Department department1 = DepartmentDraft.$.produce(draft -> {
             draft.setName("Develop");
             draft.addIntoEmployees(emp -> {