How do I create a Dynamic Sql Query at runtime using JDBI's Sql Object API?

问题

I've been moving an existing project from jdbc to jdbi, and I've been making much use out of jdbi's beautiful SQL Object API. We're using mysql.

While the SQL Object API can construct handled queries that are known at compile time, I couldn't find a way of generating queries at run time.

Specifically, I want to be able to do something like this:

@SqlUpdate(
  "UPDATE record SET "+
    @IfNotZero("foo") "foo=:foo" +
    @IfNotNull("bar") "bar=:bar" +
    @IfNotNull("baz") "baz=:baz" +
  "WHERE id=:id"
)
public abstract int updateRecord(
  @Bind("id") int id,
  @Bind("foo") int foo,
  @Bind("bar") String bar,
  @Bind("baz") String baz
);

回答1:

JDBI is not very well suited for constructing dynamic queries. IMO the whole point of this library is to separate code and SQL queries as much as possible.

However, your particular case might be solved by means of SQL:

COALESCE(:foo, foo)

if 'foo' is the name of the column in the table, and :foo will resolve to NULL, then mysql SET will be effectively

SET foo=foo

i.e. it will do nothing (which is desired beaviour in your case). If :foo is not null, it will be equivalent to

SET foo=:foo

回答2:

See @Define annotation and UseStringTemplate3StatementLocator usage.

回答3:

You can write a query like this:

UPDATE record SET
  foo = CASE WHEN :foo > 0 THEN :foo ELSE foo END
, bar = CASE WHEN :bar > 0 THEN :bar ELSE bar END
, baz = CASE WHEN :baz > 0 THEN :baz ELSE bar END
WHERE id = :id

In other words, you set the column to the variable if it matches condition, otherwise set it to itself (i.e. don't set it).

来源：https://stackoverflow.com/questions/18642862/how-do-i-create-a-dynamic-sql-query-at-runtime-using-jdbis-sql-object-api

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sql

jdbi