Spring In Action 5th Edition Question

[Will Myers]

Hi,
Does Spring 5 allow you to inject a lambda into a bean via configuration?

[Craig Walls]

It depends on how you do configuration, but yes. Certainly, there's no way to do it with XML config. But if you are using JavaConfig and the bean you're creating requires a functional type, then there's no reason you couldn't just pass a lambda or method reference into the setter or constructor arg.

On the other hand, if you're asking if it's possible to declare a lambda as a bean, then I'm not so sure. I'd wonder what that would even look like. i suppose that it'd be possible to manually register a lambda as a bean by calling registerBean() on a given GenericApplicationContext, but I can't say that I've tried it. (I have used Lambdas to define a bean of a given type when calling registerBean(), but never have had the bean itself be defined as a Lambda.)

Will Myers wrote:Hi,
Does Spring 5 allow you to inject a lambda into a bean via configuration?

[meenakshi sundar]

I have never personally used, but I have seen some examples around ...

Spring 4 on Java 8

Method references with Spring's JdbcTemplate
public List<Person> getPersonList(String department) {
JdbcTemplate jt = new JdbcTemplate(this.dataSource);
return jt.query("SELECT name, age FROM person WHERE dep = ?",
ps -> ps.setString(1, "Sales"),
this::mapPerson);
}
private Person mapPerson(ResultSet rs, int rowNum) throws SQLException {
return new Person(rs.getString(1), rs.getInt(2));
}

[meenakshi sundar]

Another interesting read on the functional web framework...

functional-web-framework

[Craig Walls]

Yes, this is a good example, I often use lambdas or method references in place of a RowMapper when working with JdbcTemplate (in fact, I cover this in the book). I wasn't thinking of that use of lambdas as being DI, though...although I guess you could say that they are. I was thinking more of how you'd inject a lambda in the context of a configuration class.

meenakshi sundar wrote:I have never personally used, but I have seen some examples around ...

Spring 4 on Java 8

Method references with Spring's JdbcTemplate
public List<Person> getPersonList(String department) {
JdbcTemplate jt = new JdbcTemplate(this.dataSource);
return jt.query("SELECT name, age FROM person WHERE dep = ?",
ps -> ps.setString(1, "Sales"),
this::mapPerson);
}
private Person mapPerson(ResultSet rs, int rowNum) throws SQLException {
return new Person(rs.getString(1), rs.getInt(2));
}

[Craig Walls]

Again, another great example of using functions (lambdas or method references) in Spring. In fact, I cover this in the book, as well.

meenakshi sundar wrote:Another interesting read on the functional web framework...

functional-web-framework