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。