Fix string cast for QueryDSL predicates (fix darrachequesne#6)

Author: darrachequesne

src/main/java/org/springframework/data/jpa/datatables/repository/DataTablesUtils.java

@@ -25,6 +25,7 @@
 import com.mysema.query.BooleanBuilder;
 import com.mysema.query.support.Expressions;
 import com.mysema.query.types.Ops;
+import com.mysema.query.types.expr.StringExpression;
 import com.mysema.query.types.path.PathBuilder;
 
 public class DataTablesUtils {
@@ -124,18 +125,16 @@ public static com.mysema.query.types.Predicate getPredicate(PathBuilder<?> entit
 }
 predicate = predicate.and(entity.getBoolean(column.getData()).in(booleanValues));
 } else {
-predicate.and(
-Expressions.stringOperation(Ops.STRING_CAST, entity.get(column.getData())).in(values));
+predicate.and(getStringExpression(entity, column.getData()).in(values));
 }
 } else {
 // the filter contains only one value, add a 'WHERE .. LIKE'
 // clause
 if (isBoolean(filterValue)) {
 predicate = predicate.and(entity.getBoolean(column.getData()).eq(Boolean.valueOf(filterValue)));
 } else {
-predicate = predicate.and(
-Expressions.stringOperation(Ops.STRING_CAST, entity.get(column.getData().toLowerCase()))
-.like(getLikeFilterValue(filterValue), ESCAPE_CHAR));
+predicate = predicate.and(getStringExpression(entity, column.getData()).lower()
+.like(getLikeFilterValue(filterValue), ESCAPE_CHAR));
 }
 }
 }
@@ -148,9 +147,8 @@ public static com.mysema.query.types.Predicate getPredicate(PathBuilder<?> entit
 // add a 'WHERE .. LIKE' clause on each searchable column
 for (ColumnParameter column : input.getColumns()) {
 if (column.getSearchable()) {
-matchOneColumnPredicate = matchOneColumnPredicate
-.or(Expressions.stringOperation(Ops.STRING_CAST, entity.get(column.getData().toLowerCase()))
-.like(getLikeFilterValue(globalFilterValue), ESCAPE_CHAR));
+matchOneColumnPredicate = matchOneColumnPredicate.or(getStringExpression(entity, column.getData())
+.lower().like(getLikeFilterValue(globalFilterValue), ESCAPE_CHAR));
 }
 }
 predicate = predicate.and(matchOneColumnPredicate);
@@ -203,4 +201,9 @@ private static Expression<String> getExpression(Root<?> root, String columnData)
 private static String getLikeFilterValue(String filterValue) {
 return "%" + filterValue.toLowerCase().replaceAll("%", "\\\\" + "%").replaceAll("_", "\\\\" + "_") + "%";
 }
+
+private static StringExpression getStringExpression(PathBuilder<?> entity, String columnData) {
+return Expressions.stringOperation(Ops.STRING_CAST, entity.get(columnData));
+}
+
 }