Spring数据访问2 - 通过JDBC访问数据库

因为原生的jdbc操作太复杂，几乎都是建立连接、关闭连接和处理例外等模板式的代码，Spring对此进行了抽象——使用模板来消除样板式代码 ，JdbcTemplate承担了简化数据库访问这块的任务。

利用JdbcTemplate实现简单的 JDBC 操作

• query
• queryForObject
• queryForList
• update
• execute

@Slf4j
@Repository
public class FooDao {
    @Autowired
    private JdbcTemplate jdbcTemplate;
    @Autowired
    private SimpleJdbcInsert simpleJdbcInsert;

    public void insertData() {
        Arrays.asList("b", "c").forEach(bar -> {
            jdbcTemplate.update("INSERT INTO FOO (BAR) VALUES (?)", bar);
        });

        HashMap<String, String> row = new HashMap<>();
        row.put("BAR", "d");
        Number id = simpleJdbcInsert.executeAndReturnKey(row);
        log.info("ID of d: {}", id.longValue());
    }

    public void listData() {
        log.info("Count: {}",
                jdbcTemplate.queryForObject("SELECT COUNT(*) FROM FOO", Long.class));

        List<String> list = jdbcTemplate.queryForList("SELECT BAR FROM FOO", String.class);
        list.forEach(s -> log.info("Bar: {}", s));

        List<Foo> fooList = jdbcTemplate.query("SELECT * FROM FOO", new RowMapper<Foo>() {
            @Override
            public Foo mapRow(ResultSet rs, int rowNum) throws SQLException {
                return Foo.builder()
                        .id(rs.getLong(1))
                        .bar(rs.getString(2))
                        .build();
            }
        });
        fooList.forEach(f -> log.info("Foo: {}", f));
    }
}

SQL批处理

JdbcTemplate

• batchUpdate
• BatchPreparedStatementSetter

NamedParameterJdbcTemplate

• batchUpdate
• SqlParameterSourceUtils.createBatch

public void batchInsert() {
        jdbcTemplate.batchUpdate("INSERT INTO FOO (BAR) VALUES (?)",
                new BatchPreparedStatementSetter() {
                    @Override
                    public void setValues(PreparedStatement ps, int i) throws SQLException {
                        ps.setString(1, "b-" + i);
                    }

                    @Override
                    public int getBatchSize() {
                        return 2;
                    }
                });

        List<Foo> list = new ArrayList<>();
        list.add(Foo.builder().id(100L).bar("b-100").build());
        list.add(Foo.builder().id(101L).bar("b-101").build());
        namedParameterJdbcTemplate
                .batchUpdate("INSERT INTO FOO (ID, BAR) VALUES (:id, :bar)",
                        SqlParameterSourceUtils.createBatch(list));
    }