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Add more lambda expressions in data-access code examples #24398

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061a9e6
more java8 lambda expressions in code examples
maxxedev Jan 20, 2020
b2ee97a
more polishing on variable name and style.
maxxedev Feb 6, 2020
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98 changes: 42 additions & 56 deletions src/docs/asciidoc/data-access.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -2715,7 +2715,7 @@ The following query looks for a `String`:
----
String lastName = this.jdbcTemplate.queryForObject(
"select last_name from t_actor where id = ?",
new Object[]{1212L}, String.class);
String.class, 1212L);
----
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
.Kotlin
Expand All @@ -2732,15 +2732,13 @@ The following query finds and populates a single domain object:
----
Actor actor = this.jdbcTemplate.queryForObject(
"select first_name, last_name from t_actor where id = ?",
new Object[]{1212L},
new RowMapper<Actor>() {
public Actor mapRow(ResultSet rs, int rowNum) throws SQLException {
Actor actor = new Actor();
actor.setFirstName(rs.getString("first_name"));
actor.setLastName(rs.getString("last_name"));
return actor;
}
});
(resultSet, rowNum) -> {
Actor newActor = new Actor();
newActor.setFirstName(resultSet.getString("first_name"));
newActor.setLastName(resultSet.getString("last_name"));
return newActor;
},
1212L);
----
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
.Kotlin
Expand All @@ -2759,13 +2757,11 @@ The following query finds and populates a number of domain objects:
----
List<Actor> actors = this.jdbcTemplate.query(
"select first_name, last_name from t_actor",
new RowMapper<Actor>() {
public Actor mapRow(ResultSet rs, int rowNum) throws SQLException {
Actor actor = new Actor();
actor.setFirstName(rs.getString("first_name"));
actor.setLastName(rs.getString("last_name"));
return actor;
}
(resultSet, rowNum) -> {
Actor actor = new Actor();
actor.setFirstName(resultSet.getString("first_name"));
actor.setLastName(resultSet.getString("last_name"));
return actor;
});
----
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
Expand All @@ -2777,27 +2773,25 @@ The following query finds and populates a number of domain objects:


If the last two snippets of code actually existed in the same application, it would make
sense to remove the duplication present in the two `RowMapper` anonymous inner classes
and extract them out into a single class (typically a `static` nested class) that could
then be referenced by DAO methods as needed. For example, it may be better to write the
preceding code snippet as follows:
sense to remove the duplication present in the two `RowMapper` lambda expressions and
extract them out into a single field that could then be referenced by DAO methods as needed.
For example, it may be better to write the preceding code snippet as follows:

[source,java,indent=0,subs="verbatim,quotes",role="primary"]
.Java
----
public List<Actor> findAllActors() {
return this.jdbcTemplate.query( "select first_name, last_name from t_actor", new ActorMapper());
}

private static final class ActorMapper implements RowMapper<Actor> {
private final RowMapper<Actor> actorRowMapper = (resultSet, rowNum) -> {
Actor actor = new Actor();
actor.setFirstName(resultSet.getString("first_name"));
actor.setLastName(resultSet.getString("last_name"));
return actor;
};

public Actor mapRow(ResultSet rs, int rowNum) throws SQLException {
Actor actor = new Actor();
actor.setFirstName(rs.getString("first_name"));
actor.setLastName(rs.getString("last_name"));
return actor;
}
public List<Actor> findAllActors() {
return this.jdbcTemplate.query( "select first_name, last_name from t_actor", actorRowMapper);
}

----
[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
.Kotlin
Expand Down Expand Up @@ -3562,15 +3556,11 @@ on Oracle but may not work on other platforms:
final String name = "Rob";

KeyHolder keyHolder = new GeneratedKeyHolder();
jdbcTemplate.update(
new PreparedStatementCreator() {
public PreparedStatement createPreparedStatement(Connection connection) throws SQLException {
PreparedStatement ps = connection.prepareStatement(INSERT_SQL, new String[] {"id"});
ps.setString(1, name);
return ps;
}
},
keyHolder);
jdbcTemplate.update(connection -> {
PreparedStatement ps = connection.prepareStatement(INSERT_SQL, new String[] { "id" });
ps.setString(1, name);
return ps;
}, keyHolder);

// keyHolder.getKey() now contains the generated key
----
Expand Down Expand Up @@ -4053,12 +4043,10 @@ The following example shows a batch update that uses a batch size of 100:
"update t_actor set first_name = ?, last_name = ? where id = ?",
actors,
100,
new ParameterizedPreparedStatementSetter<Actor>() {
public void setValues(PreparedStatement ps, Actor argument) throws SQLException {
ps.setString(1, argument.getFirstName());
ps.setString(2, argument.getLastName());
ps.setLong(3, argument.getId().longValue());
}
(PreparedStatement ps, Actor argument) -> {
ps.setString(1, argument.getFirstName());
ps.setString(2, argument.getLastName());
ps.setLong(3, argument.getId().longValue());
});
return updateCounts;
}
Expand Down Expand Up @@ -5567,16 +5555,14 @@ declared type `ITEM_TYPE`:
public TestItemStoredProcedure(DataSource dataSource) {
// ...
declareParameter(new SqlOutParameter("item", OracleTypes.STRUCT, "ITEM_TYPE",
new SqlReturnType() {
public Object getTypeValue(CallableStatement cs, int colIndx, int sqlType, String ) throws SQLException {
STRUCT struct = (STRUCT) cs.getObject(colIndx);
Object[] attr = struct.getAttributes();
TestItem item = new TestItem();
item.setId(((Number) attr[0]).longValue());
item.setDescription((String) attr[1]);
item.setExpirationDate((java.util.Date) attr[2]);
return item;
}
(CallableStatement cs, int colIndx, int sqlType, String typeName) -> {
STRUCT struct = (STRUCT) cs.getObject(colIndx);
Object[] attr = struct.getAttributes();
TestItem item = new TestItem();
item.setId(((Number) attr[0]).longValue());
item.setDescription((String) attr[1]);
item.setExpirationDate((java.util.Date) attr[2]);
return item;
}));
// ...
}
Expand Down