I can't wrap my head around how should i get my data without much boilerplate.
The problem:
I have a database that i cannot alter. Which has multiple field of same type almost same for example i have text_en and text_fr (both are the same word in different language English and French) and i got + 71 same field but different languages.
What I need is something like
#Entitiy(tableName = "blabla")
class X {
private String textTarget;
private String textMain;
...
}
How should I do my Dao interface to get desired language and map into x class
what should work is to update entity ColumnInfo(name ="text_en") for example.
#Query("select :main , :target from phrases where :id ")
List<X> getPhrase(String main,String target);
usage : getPhrase("text_en","text_esp");
// for example returning object X with field main = "hello" and target " holla")
The above example return the following error:
error: Not sure how to convert a Cursor to this method's return type
What you put in #Query is an SQL-statement, you can actually test them in sqlite command line utility or any desktop software to verify their correctness. So if you want a translation to the desired language, it should look like this:
#Query("SELECT :main AS text_main, :target AS text_target FROM `phrases` WHERE id = :id)
List<Translation> getTranslationById(String firstLang, String secondLang, long id);
Where Translation should be something like this:
class Translation {
#ColumnInfo("text_main")
String main;
#ColumnInfo("text_target")
String target;
//setters, getters, etc
}
This class is used only as a return value from the method.
I am trying to convert something like this in jOOQ:
select foo from bar
order by field(foo, 'value1', 'something-else', 'value3')
on a select query, like:
SelectQuery<Record> query = ...
query.addSelect(BAR.FOO);
query.addFrom(BAR);
query.addOrderBy( ... ? ... )
How does one add the last bit?
Background
What I am trying to accomplish is basically described here: MySQL - ORDER BY values within IN(). In my case, I have a generic batch load function that uses 'where field in(..)' and I want to preserve order. This works as I need it to using plain SQL, but I need to add this bit to a dynamically constructed query with jOOQ.
Whenever you hit jOOQ's limits, resort to plain SQL. You can write your own field function like this:
class MyDSL {
public static Field<Integer> field(Field<String> search, String in1) {
return field(search, DSL.val(in1));
}
public static Field<Integer> field(Field<String> search, Field<String> in1) {
return DSL.field("field({0}, {1})", Integer.class, search, in1);
}
public static Field<Integer> field(Field<String> search,
String in1,
String in2) {
return field(search, val(in1), val(in2));
}
public static Field<Integer> field(Field<String> search,
Field<String> in1,
Field<String> in2) {
return DSL.field("field({0}, {1}, {2})", Integer.class, search, in1, in2);
}
// ... or, support a varargs function variant, too
}
And now use that in all your statements:
query.addOrderBy( MyDSL.field(BAR.FOO, "value1", "something-else", "value3") );
This seems to do the trick. Not sure if there is a better answer,
Field[] args = new Field[]{DSL.field("foo"),
DSL.val("value1"), DSL.val("something-else"), DSL.val("value3")}
query.addOrderBy(DSL.function("field", SQLDataType.INTEGER, args));
You can use something like to convert following sql to jooq. Here 'sortAsc' is used to sort according to the given value order.
SQL
select foo from bar order by field(foo, 'value1', 'something-else', 'value3')
JOOQ
DSL()
.select(BAR.FOO)
.from(BAR)
.orderBy(BAR.FOO.sortAsc('value11', 'something-else', 'value3'))
.fetch()
In the table is a pk with uuid's stored as binary(16).
I'm able to retrieve the hexadecimal using plain sql:
select hex(UUID) as uuid from tbl ;
But the jooq equivalent does not know a hex function.
Result<Record1<byte[]>> result = ctx
.select(tbl.UUID)
.from(tbl)
.fetch();
Casting to String gives the id of the java object.
Any idea's?
Result<Record1<byte[]>> result = ctx
.select(tbl.UUID.cast(String.class))
.from(tbl)
.fetch();
Same problem using ip's (ipv4, ipv6):
select inet_ntoa(conv(hex(IP), 16, 10)) as ip from tbl ;
jOOQ doesn't support all vendor-specific functions out of the box. Whenever you are missing such a function, you can create it yourself using plain SQL:
public class DSLExtensions {
public static Field<String> hex(Field<byte[]> field) {
return DSL.field("hex({0})", String.class, field);
}
}
This obviously holds true for your other functions, too, such as inet_ntoa() and conv()
#Lukas Eder, you can simplify that even more.
public static Field<String> hex(Field<byte[]> field) {
return DSL.function("hex", String.class, field);
}
I want to make SQL look like:
select b from Book b order by rand()
how convert that query to Querydsl query?
Is it not supported by Querydsl?
If you know the way to support this query, please answer it..;
thank you.
Querydsl SQL supports it via
NumberExpression.random()
So your query could be expressed like this
query.from(b)
.orderBy(NumberExpression.random().asc())
.list(b);
I am not sure how well it is supported for JPQL, it doesn't seem to be in the standard.
A addition to Timo's answer.
If you use mysql you will get the error "ERROR: FUNCTION schema.random does not exist", this is because mysql has a RAND function instead of a RANDOM function. To fix this you can either add the random function in sql, like this:
DROP FUNCTION IF EXISTS RANDOM;
DELIMITER $$
CREATE FUNCTION RANDOM ()
RETURNS DECIMAL(15,15)
DETERMINISTIC
BEGIN
DECLARE dist DECIMAL(15,15);
SET dist = RAND();
RETURN dist;
END$$
DELIMITER ;
Or fix the random function to use rand with:
public class MySQLJPATemplates extends JPQLTemplates {
public static final MySQLJPATemplates DEFAULT = new MySQLJPATemplates();
public MySQLJPATemplates() {
this(DEFAULT_ESCAPE);
add(Ops.MathOps.RANDOM, "rand()");
add(Ops.MathOps.RANDOM2, "rand({0})");
}
public MySQLJPATemplates(char escape) {
super(escape);
}
}
And use the template as follows:
JPAQuery<Route> query = new JPAQuery<Route>(em, MySQLJPATemplates.DEFAULT);
query.from(b)
.orderBy(NumberExpression.random().asc())
.list(b);
We'd like to use only annotations with MyBatis; we're really trying to avoid xml. We're trying to use an "IN" clause:
#Select("SELECT * FROM blog WHERE id IN (#{ids})")
List<Blog> selectBlogs(int[] ids);
MyBatis doesn't seem able to pick out the array of ints and put those into the resulting query. It seems to "fail softly" and we get no results back.
It looks like we could accomplish this using XML mappings, but we'd really like to avoid that. Is there a correct annotation syntax for this?
I believe the answer is the same as is given in this question. You can use myBatis Dynamic SQL in your annotations by doing the following:
#Select({"<script>",
"SELECT *",
"FROM blog",
"WHERE id IN",
"<foreach item='item' index='index' collection='list'",
"open='(' separator=',' close=')'>",
"#{item}",
"</foreach>",
"</script>"})
List<Blog> selectBlogs(#Param("list") int[] ids);
The <script> element enables dynamic SQL parsing and execution for the annotation. It must be very first content of the query string. Nothing must be in front of it, not even white space.
Note that the variables that you can use in the various XML script tags follow the same naming conventions as regular queries, so if you want to refer to your method arguments using names other than "param1", "param2", etc... you need to prefix each argument with an #Param annotation.
I believe this is a nuance of jdbc's prepared statements and not MyBatis. There is a link here that explains this problem and offers various solutions. Unfortunately, none of these solutions are viable for your application, however, its still a good read to understand the limitations of prepared statements with regards to an "IN" clause. A solution (maybe suboptimal) can be found on the DB-specific side of things. For example, in postgresql, one could use:
"SELECT * FROM blog WHERE id=ANY(#{blogIds}::int[])"
"ANY" is the same as "IN" and "::int[]" is type casting the argument into an array of ints. The argument that is fed into the statement should look something like:
"{1,2,3,4}"
Had some research on this topic.
one of official solution from mybatis is to put your dynamic sql in #Select("<script>...</script>"). However, writing xml in java annotation is quite ungraceful. think about this #Select("<script>select name from sometable where id in <foreach collection=\"items\" item=\"item\" seperator=\",\" open=\"(\" close=\")\">${item}</script>")
#SelectProvider works fine. But it's a little complicated to read.
PreparedStatement not allow you set list of integer. pstm.setString(index, "1,2,3,4") will let your SQL like this select name from sometable where id in ('1,2,3,4'). Mysql will convert chars '1,2,3,4' to number 1.
FIND_IN_SET don't works with mysql index.
Look in to mybatis dynamic sql mechanism, it has been implemented by SqlNode.apply(DynamicContext). However, #Select without <script></script> annotation will not pass parameter via DynamicContext
see also
org.apache.ibatis.scripting.xmltags.XMLLanguageDriver
org.apache.ibatis.scripting.xmltags.DynamicSqlSource
org.apache.ibatis.scripting.xmltags.RawSqlSource
So,
Solution 1: Use #SelectProvider
Solution 2: Extend LanguageDriver which will always compile sql to DynamicSqlSource. However, you still have to write \" everywhere.
Solution 3: Extend LanguageDriver which can convert your own grammar to mybatis one.
Solution 4: Write your own LanguageDriver which compile SQL with some template renderer, just like mybatis-velocity project does. In this way, you can even integrate groovy.
My project take solution 3 and here's the code:
public class MybatisExtendedLanguageDriver extends XMLLanguageDriver
implements LanguageDriver {
private final Pattern inPattern = Pattern.compile("\\(#\\{(\\w+)\\}\\)");
public SqlSource createSqlSource(Configuration configuration, String script, Class<?> parameterType) {
Matcher matcher = inPattern.matcher(script);
if (matcher.find()) {
script = matcher.replaceAll("(<foreach collection=\"$1\" item=\"__item\" separator=\",\" >#{__item}</foreach>)");
}
script = "<script>" + script + "</script>";
return super.createSqlSource(configuration, script, parameterType);
}
}
And the usage:
#Lang(MybatisExtendedLanguageDriver.class)
#Select("SELECT " + COLUMNS + " FROM sometable where id IN (#{ids})")
List<SomeItem> loadByIds(#Param("ids") List<Integer> ids);
I've made a small trick in my code.
public class MyHandler implements TypeHandler {
public void setParameter(PreparedStatement ps, int i, Object parameter, JdbcType jdbcType) throws SQLException {
Integer[] arrParam = (Integer[]) parameter;
String inString = "";
for(Integer element : arrParam){
inString = "," + element;
}
inString = inString.substring(1);
ps.setString(i,inString);
}
And I used this MyHandler in SqlMapper :
#Select("select id from tmo where id_parent in (#{ids, typeHandler=ru.transsys.test.MyHandler})")
public List<Double> getSubObjects(#Param("ids") Integer[] ids) throws SQLException;
It works now :)
I hope this will help someone.
Evgeny
Other option can be
public class Test
{
#SuppressWarnings("unchecked")
public static String getTestQuery(Map<String, Object> params)
{
List<String> idList = (List<String>) params.get("idList");
StringBuilder sql = new StringBuilder();
sql.append("SELECT * FROM blog WHERE id in (");
for (String id : idList)
{
if (idList.indexOf(id) > 0)
sql.append(",");
sql.append("'").append(id).append("'");
}
sql.append(")");
return sql.toString();
}
public interface TestMapper
{
#SelectProvider(type = Test.class, method = "getTestQuery")
List<Blog> selectBlogs(#Param("idList") int[] ids);
}
}
In my project, we are already using Google Guava, so a quick shortcut is.
public class ListTypeHandler implements TypeHandler {
#Override
public void setParameter(PreparedStatement ps, int i, Object parameter, JdbcType jdbcType) throws SQLException {
ps.setString(i, Joiner.on(",").join((Collection) parameter));
}
}
In Oracle, I use a variant of Tom Kyte's tokenizer to handle unknown list sizes (given Oracle's 1k limit on an IN clause and the aggravation of doing multiple INs to get around it). This is for varchar2, but it can be tailored for numbers (or you could just rely on Oracle knowing that '1' = 1 /shudder).
Assuming you pass or perform myBatis incantations to get ids as a String, to use it:
select #Select("SELECT * FROM blog WHERE id IN (select * from table(string_tokenizer(#{ids}))")
The code:
create or replace function string_tokenizer(p_string in varchar2, p_separator in varchar2 := ',') return sys.dbms_debug_vc2coll is
return_value SYS.DBMS_DEBUG_VC2COLL;
pattern varchar2(250);
begin
pattern := '[^(''' || p_separator || ''')]+' ;
select
trim(regexp_substr(p_string, pattern, 1, level)) token
bulk collect into
return_value
from
dual
where
regexp_substr(p_string, pattern, 1, level) is not null
connect by
regexp_instr(p_string, pattern, 1, level) > 0;
return return_value;
end string_tokenizer;
You could use a custom type handler to do this. For example:
public class InClauseParams extends ArrayList<String> {
//...
// marker class for easier type handling, and avoid potential conflict with other list handlers
}
Register the following type handler in your MyBatis config (or specify in your annotation):
public class InClauseTypeHandler extends BaseTypeHandler<InClauseParams> {
#Override
public void setNonNullParameter(final PreparedStatement ps, final int i, final InClauseParams parameter, final JdbcType jdbcType) throws SQLException {
// MySQL driver does not support this :/
Array array = ps.getConnection().createArrayOf( "VARCHAR", parameter.toArray() );
ps.setArray( i, array );
}
// other required methods omitted for brevity, just add a NOOP implementation
}
You can then use them like this
#Select("SELECT * FROM foo WHERE id IN (#{list})"
List<Bar> select(#Param("list") InClauseParams params)
However, this will not work for MySQL, because the MySQL connector does not support setArray() for prepared statements.
A possible workaround for MySQL is to use FIND_IN_SET instead of IN:
#Select("SELECT * FROM foo WHERE FIND_IN_SET(id, #{list}) > 0")
List<Bar> select(#Param("list") InClauseParams params)
And your type handler becomes:
#Override
public void setNonNullParameter(final PreparedStatement ps, final int i, final InClauseParams parameter, final JdbcType jdbcType) throws SQLException {
// note: using Guava Joiner!
ps.setString( i, Joiner.on( ',' ).join( parameter ) );
}
Note: I don't know the performance of FIND_IN_SET, so test this if it is important
I had done this with postgresql.
#Update('''
UPDATE sample_table
SET start = null, finish = null
WHERE id=ANY(#{id});
''')
int resetData(#Param("id") String[] id)
ANY works like the IN.
Code above is using groovy but can be converted into java by replacing the single quotes into double.