Spring MVC系列之JDBC Demo（SpringBoot）（八）

前言

前面我们了解了Spring MVC的基本使用，其实和.NET或.NET Core MVC无异，只是语法不同而已罢了，本节我们将和和数据库打交道，从最基础的JDBC讲解起，文中若有错误之处，还望指正。

JDBC Demo

我们需要下载三个包：JDBC驱动包(mysql-connector-java)、spring boot启用jdbc(spring-boot-starter-jdbc)、对数据进行序列化的json包(jackson-databind)，如下：

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
</dependency>

接下来我们在配置文件中，通过JDBC连接MySQL数据库，如下：

spring.datasource.url = jdbc:mysql://localhost:3306/user?serverTimezone=UTC
spring.datasource.username = root
spring.datasource.password = root

这里需要注意的是：对于不同的JDBC驱动版本，可能会抛出如下错误，这是由于在JDBC指定版本中存在的bug，所以要么如上显式指定serverTimezone，要么添加JDBC版本

The server time zone value '�й���׼ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver 
(via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support

接下来我们定义对用户进行增、删、改、查的接口，如下：

public interface UserRepository {

    int save(User user);

    int update(User user);

    int deleteById(int id);

    List<User> findAll();

}

接下来我们再来看用户类，我们将对提交用户信息通过注解进行校验，同时我们对之前添加的爱好的数据类型为数组序列化为JSON后存到MySQL数据库，如下：

public class User {

    private ObjectMapper objectMapper = new ObjectMapper();

    public User() {
    }

    public User(int userId,
                String firstName,
                String lastName,
                String gender,
                String email,
                String userName,
                String password,
                String country,
                String favoritesJson) throws JsonProcessingException {
        this.userId = userId;
        this.firstName = firstName;
        this.lastName = lastName;
        this.gender = gender;
        this.email = email;
        this.userName = userName;
        this.password = password;
        this.country = country;

        this.favorites = objectMapper.readValue(favoritesJson, new TypeReference<String[]>() {
        });
    }

    private int userId;
    @NotNull(message = "名字必填")
    private String firstName;
    @NotNull(message = "姓氏必填")
    private String lastName;
    @NotNull(message = "性别必填")
    private String gender;
    @NotNull(message = "邮箱必填")
    @Email(message = "请输入有效的邮箱")
    private String email;
    @NotNull(message = "用户名必填")
    private String userName;
    @NotNull(message = "密码必填")
    private String password;
    private String country;

    public int getUserId() {
        return userId;
    }

    public String getFavoritesJson() {
        String favoritesJson = null;
        try {
            favoritesJson = objectMapper.writeValueAsString(this.favorites);
        } catch (JsonProcessingException ex) {
        }
        return favoritesJson;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    private String[] favorites;

    public String[] getFavorites() {
        return favorites;
    }

    public void setFavorites(String[] favorites) {
        this.favorites = favorites;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

最后则是实现上述用户接口，这里我们使用JDBC中的参数化类（避免SQL注入）进行增删改查，如下：

@Repository
public class NamedParameterJdbcUserRepository implements UserRepository {

    @Autowired
    public NamedParameterJdbcTemplate namedParameterJdbcTemplate;

    @Override
    public int save(User user) {
        MapSqlParameterSource mapSqlParameterSource = new MapSqlParameterSource();
        mapSqlParameterSource.addValue("userName",user.getUserName());
        mapSqlParameterSource.addValue("password",user.getPassword());
        mapSqlParameterSource.addValue("firstName",user.getFirstName());
        mapSqlParameterSource.addValue("lastName",user.getLastName());
        mapSqlParameterSource.addValue("gender",user.getGender());
        mapSqlParameterSource.addValue("email",user.getEmail());
        mapSqlParameterSource.addValue("country",user.getCountry());
        mapSqlParameterSource.addValue("favorites",user.getFavoritesJson());

        return namedParameterJdbcTemplate.update(
                "insert into users (userName, password,firstName,lastName,gender,email,country,favorites)" +
                        " values(:userName,:password,:firstName,:lastName,:gender,:email,:country,:favorites)",
             mapSqlParameterSource);
    }

    @Override
    public int update(User user) {
        return 0;
    }

    @Override
    public int deleteById(int id) {
        MapSqlParameterSource mapSqlParameterSource = new MapSqlParameterSource();
        mapSqlParameterSource.addValue("userId", id);
        return namedParameterJdbcTemplate.update("delete from  users where userId = :userId", mapSqlParameterSource);
    }

    @Override
    public List<User> findAll() {
        return namedParameterJdbcTemplate.query(
                "select * from users",
                (rs, rowNum) ->
                {
                    try {
                        return new User(
                                rs.getInt("userId"),
                                rs.getString("firstName"),
                                rs.getString("lastName"),
                                rs.getString("gender"),
                                rs.getString("email"),
                                rs.getString("userName"),
                                rs.getString("password"),
                                rs.getString("country"),
                                rs.getString("favorites")
                        );
                    } catch (JsonProcessingException e) {
                        e.printStackTrace();
                        return null;
                    }
                });
    }
}

然后在进行提交用户时，在上一节内容基础上进行改造，添加校验注解，若有错误则返回，否则提交成功后则跳转到用户列表，如下：

    @RequestMapping(value = "/user", method = RequestMethod.POST)
    public String user(@Valid @ModelAttribute("user") User user, BindingResult bindingResult) {
        if (bindingResult.hasErrors()) {
            return "user";
        } else {
            jdbcUserRepository.save(user);
            return "users";
        }
    }

这里需要注意的是：对于空字符串即使添加了校验注解后依然会忽略，所以我们还需要初始化绑定器注解去除空字符串并对其进行校验，如下：

    @InitBinder
    public void initBinder(WebDataBinder dataBinder) {

        StringTrimmerEditor stringTrimmerEditor = new StringTrimmerEditor(true);

        dataBinder.registerCustomEditor(String.class, stringTrimmerEditor);
    }

表单提交我们使用的是spring提供给我们的库，渲染用户列表，我们则是通过脚本并利用bootstrap-table实现，最终界面所呈现出的效果，如下： 

 

总结

如上只是给出了部分重要代码，这里我已经将本节通过JDBC进行增删改查代码上传到github（https://github.com/wangpengxpy/SpringBoot），切换分支即可，后续会将每一块内容分别创建一个分支，以便供我复习和有需要的童鞋使用，本节我们到此结束，我们下节见。