keyHolder.getKey() 返回 null。

Question

为什么《Spring实战第五版》的代码不起作用（keyHolder.getKey()返回null，但实体已保存在数据库中）？

private long savePizzaInfo(Pizza pizza) {
    pizza.setCreatedAt(new Date());
    PreparedStatementCreator psc =
            new PreparedStatementCreatorFactory(
                    "insert into PIZZA (name, createdAt) values (?, ?)",
                    Types.VARCHAR, Types.TIMESTAMP
            ).newPreparedStatementCreator(
                    Arrays.asList(
                            pizza.getName(),
                            new Timestamp(pizza.getCreatedAt().getTime())));
    KeyHolder keyHolder = new GeneratedKeyHolder();
    template.update(psc, keyHolder);
    return keyHolder.getKey().longValue();
}

我的数据库表：

CREATE TABLE PIZZA
(
ID bigint DEFAULT (NEXT VALUE FOR 
PUBLIC.SYSTEM_SEQUENCE_12CA966F_4FFD_469C_BA69_80BB93916EF3) AUTO_INCREMENT 
PRIMARY KEY NOT NULL,
NAME varchar(50) NOT NULL,
CREATEDAT timestamp NOT NULL
);
CREATE UNIQUE INDEX PRIMARY_KEY_4 ON PIZZA (ID);

- lobs

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“PreparedStatementCreatorFactory return null” 是什么意思？ - user10639668

对不起，错误发生了，KeyHolder 返回 null。 - lobs

你的意思是 keyHolder.getKey() 返回了null？ - user10639668

是的，keyHolder.getKey() 返回 null。 - lobs

Answer 1

你必须指示PreparedStatementCreatorFactory实例返回生成的键：

PreparedStatementCreatorFactory preparedStatementCreatorFactory = new PreparedStatementCreatorFactory(
         "insert into PIZZA (name, createdAt) values (?, ?)",
         Types.VARCHAR, Types.TIMESTAMP
 );

// By default, returnGeneratedKeys = false so change it to true
preparedStatementCreatorFactory.setReturnGeneratedKeys(true);

 PreparedStatementCreator psc =
         preparedStatementCreatorFactory.newPreparedStatementCreator(
                    Arrays.asList(
                            pizza.getName(),
                            new Timestamp(pizza.getCreatedAt().getTime())));

- user10639668

Answer 2

您需要指定您的预编译语句，注意下面示例代码中的Statement.RETURN_GENERATED_KEYS。您需要像这样做：

final PreparedStatementCreator psc = new PreparedStatementCreator() {
      @Override
      public PreparedStatement createPreparedStatement(final Connection connection) throws SQLException {
        final PreparedStatement ps = connection.prepareStatement("INSERT INTO `names` (`name`) VALUES (?)",
            Statement.RETURN_GENERATED_KEYS);
        ps.setString(1, name);
        return ps;
      }
    };

- MC Ninjava

Answer 3

为什么不使用SimpleJdbcInsert呢？

dbcInsert = new SimpleJdbcInsert(jdbcTemplate);
        jdbcInsert.withTableName("TABLE_NAME").usingGeneratedKeyColumns(
                "Primary_key");
        Map<String, Object> parameters = new HashMap<>();
        parameters.put("Column_NAME1", bean.getval1());
        parameters.put("Column_NAME2", bean.getval2());
        // execute insert
        Number key = jdbcInsert.executeAndReturnKey(new MapSqlParameterSource(
                parameters));
           // convert Number to Int using ((Number) key).intValue()
            return ((Number) key).intValue();

- Sheetal Mohan Sharma

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这将在本书后面使用。 - Adel Khial