使用RowMapper和JdbcTemplate有NullPointerException
我有两个实体 - 用户和访问组。 当在JdbcTemplate中使用RowMapper从MySQL数据库获取用户实体时,我有NullPointerException。 在UserRowMapper中不使用setter作为accessgroup时,我没有NPE,但在AccessGroup accessGroup中有空。
表
CREATE TABLE `users` ( `USER_ID` int(11) NOT NULL AUTO_INCREMENT, `USER_EMAIL` varchar(255) DEFAULT NULL, `USER_NAME` varchar(255) DEFAULT NULL, `USER_PWD` varchar(255) DEFAULT NULL, `ACCESSGROUP_GROUP_ID` int(11) DEFAULT NULL, PRIMARY KEY (`USER_ID`), KEY `FK_users_ACCESSGROUP_GROUP_ID` (`ACCESSGROUP_GROUP_ID`), CONSTRAINT `FK_users_ACCESSGROUP_GROUP_ID` FOREIGN KEY (`ACCESSGROUP_GROUP_ID`) REFERENCES `access_group` (`GROUP_ID`) ) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=latin1;
CREATE TABLE `access_group` ( `GROUP_ID` int(11) NOT NULL AUTO_INCREMENT, `GROUP_NAME` varchar(255) NOT NULL DEFAULT '', PRIMARY KEY (`GROUP_ID`) ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=latin1;
实体
@Entity @Table(name = "users") public class User implements Serializable { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Basic(optional = false) @Column(name = "USER_ID") private Integer userId; @Column(name = "USER_EMAIL") private String userEmail; @Column(name = "USER_NAME") private String userName; @Column(name = "USER_PWD") private String userPwd; @JoinColumn(name = "ACCESSGROUP_GROUP_ID", referencedColumnName = "GROUP_ID") @ManyToOne private AccessGroup accessGroup;
@Entity @Table(name = "access_group") public class AccessGroup implements Serializable { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Basic(optional = false) @Column(name = "GROUP_ID") private Integer groupId; @Basic(optional = false) @Column(name = "GROUP_NAME") private String groupName; @OneToMany(mappedBy = "accessGroup") private Set users;
道
@Repository("userDao") public class UserDaoImpl implements IUserDao { @Autowired private JdbcTemplate jdbcTemplate; @Value("${sql.user.get.email.pwd}") private String getByEmailAndPwd; //sql.user.get.email.pwd=SELECT * FROM users WHERE user_email = ? AND user_pwd = ? @Transactional @Override public User getUserByEmailAndPwd(String email, String password) { return jdbcTemplate.queryForObject(getByEmailAndPwd, new Object[]{email, password}, new UserRowMapper()); }
@Repository("accessGroupDao") public class AccessGroupDaoImpl implements IAccessGroupDao { private JdbcTemplate jdbcTemplate; @Autowired public void setJdbcTemplate(JdbcTemplate jdbcTemplate) { this.jdbcTemplate = jdbcTemplate; } @Value("${sql.accessgroup.get.id}") private String getAccessGroupById; //sql.accessgroup.get.id=SELECT * FROM access_group WHERE GROUP_ID = ? @Transactional @Override public AccessGroup getGroupById(int id) { return jdbcTemplate.queryForObject(getAccessGroupById, new Object[]{id}, new AccessGroupRowMapper()); }
RowMappers
@Component public class UserRowMapper implements RowMapper { private AccessGroupService accessGroupService; @Autowired public void setAccessGroupService(AccessGroupService accessGroupService) { this.accessGroupService = accessGroupService; } @Override public User mapRow(ResultSet resultSet, int i) throws SQLException { User user = new User(); user.setId(resultSet.getInt("USER_ID")); user.setEmail(resultSet.getString("USER_EMAIL")); user.setName(resultSet.getString("USER_NAME")); user.setpwd(resultSet.getString("USER_PWD")); //when adding here user.setAccessGroup(accessGroupService.getGroupById(resultSet.getInt("ACCESSGROUP_GROUP_ID"))); I have NPE return user; }
public class AccessGroupRowMapper implements RowMapper { @Override public AccessGroup mapRow(ResultSet resultSet, int i) throws SQLException { AccessGroup accessGroup = new AccessGroup(); accessGroup.setId(resultSet.getInt("GROUP_ID")); accessGroup.setName(resultSet.getString("GROUP_NAME")); return accessGroup; } }
1)将以下属性添加到您的@Entity类'User'并生成getter&setter方法:
@Transient
private Integer userIdTransientField;
@Transient表示该属性不会存储在数据库中
2)修改RowMapper类:
将此行替换为以下内容:
user.setId(resultSet.getInt("USER_ID")); -> user.setUserIdTransientField(resultSet.getInt("USER_ID"));
3)当您引用'User'对象并且想要为jdbcTemplate执行Update / Delete或仅想获取Id值时,请使用getUserIdTransientField方法。
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