1、添加数据源
既然要使用JdbcTemplate，就需要添加jdbc的依赖。
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
2、连接数据源，以mysql为例：
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
3、在src/main/resources/application.properties中配置数据源信息
注意：其中driver-class可以不写，Spring Boot会自动从url中解析使用的数据源类
Spring Boot默认采用tomcat-jdbc连接池，如果需要C3P0，DBCP，Druid等作为连接池，需要加入相关依赖以及配置，这里不作说明，采用默认配置即可。
spring.datasource.driver-class-name=com.mysql.jdbc.Driver spring.datasource.url=jdbc:mysql://localhost:3306/test spring.datasource.username=... spring.datasource.password=...
底层默认使用tomcat-jdbc连接池，所以在默认情况下会创建一个基于Tomcat连接池的DataSource，并注入到Spring IOC容器中。
abstract class DataSourceConfiguration {
@SuppressWarnings("unchecked")
protected <T> T createDataSource(DataSourceProperties properties,
Class<? extends DataSource> type) {
return (T) properties.initializeDataSourceBuilder().type(type).build();
}
/**
* Tomcat Pool DataSource configuration.
*/
@ConditionalOnClass(org.apache.tomcat.jdbc.pool.DataSource.class)
@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.tomcat.jdbc.pool.DataSource", matchIfMissing = true)
static class Tomcat extends DataSourceConfiguration {
//创建一个基于Tomcat连接池的DataSource的Bean
//由于底层使用Tomcat连接池，在不引入外部数据连接池的jar包之前，默认使用Tomcat的DataSource
@Bean
@ConfigurationProperties(prefix = "spring.datasource.tomcat")
public org.apache.tomcat.jdbc.pool.DataSource dataSource(
DataSourceProperties properties) {
org.apache.tomcat.jdbc.pool.DataSource dataSource = createDataSource(
properties, org.apache.tomcat.jdbc.pool.DataSource.class);
DatabaseDriver databaseDriver = DatabaseDriver
.fromJdbcUrl(properties.determineUrl());
String validationQuery = databaseDriver.getValidationQuery();
if (validationQuery != null) {
dataSource.setTestOnBorrow(true);
dataSource.setValidationQuery(validationQuery);
}
return dataSource;
}
}
/**
* Hikari DataSource configuration.
*/
@ConditionalOnClass(HikariDataSource.class)
@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "com.zaxxer.hikari.HikariDataSource", matchIfMissing = true)
static class Hikari extends DataSourceConfiguration {
//创建基于hikari的DataSource的Bean
@Bean
@ConfigurationProperties(prefix = "spring.datasource.hikari")
public HikariDataSource dataSource(DataSourceProperties properties) {
return createDataSource(properties, HikariDataSource.class);
}
}
/**
* DBCP DataSource configuration.
*
* @deprecated as of 1.5 in favor of DBCP2
*/
@ConditionalOnClass(org.apache.commons.dbcp.BasicDataSource.class)
@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.commons.dbcp.BasicDataSource", matchIfMissing = true)
@Deprecated
static class Dbcp extends DataSourceConfiguration {
//创建基于dbcp的DataSource的Bean
@Bean
@ConfigurationProperties(prefix = "spring.datasource.dbcp")
public org.apache.commons.dbcp.BasicDataSource dataSource(
DataSourceProperties properties) {
org.apache.commons.dbcp.BasicDataSource dataSource = createDataSource(
properties, org.apache.commons.dbcp.BasicDataSource.class);
DatabaseDriver databaseDriver = DatabaseDriver
.fromJdbcUrl(properties.determineUrl());
String validationQuery = databaseDriver.getValidationQuery();
if (validationQuery != null) {
dataSource.setTestOnBorrow(true);
dataSource.setValidationQuery(validationQuery);
}
return dataSource;
}
}
/**
* DBCP DataSource configuration.
*/
@ConditionalOnClass(org.apache.commons.dbcp2.BasicDataSource.class)
@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.commons.dbcp2.BasicDataSource", matchIfMissing = true)
static class Dbcp2 extends DataSourceConfiguration {
//创建基于dbcp2的DataSource的Bean
@Bean
@ConfigurationProperties(prefix = "spring.datasource.dbcp2")
public org.apache.commons.dbcp2.BasicDataSource dataSource(
DataSourceProperties properties) {
return createDataSource(properties,
org.apache.commons.dbcp2.BasicDataSource.class);
}
}
/**
* Generic DataSource configuration.
*/
@ConditionalOnMissingBean(DataSource.class)
@ConditionalOnProperty(name = "spring.datasource.type")
static class Generic {
//可以在配置文件中通过spring.datasource.type指定外部的dataSource类型，并创建基于该type的DataSource的Bean
@Bean
public DataSource dataSource(DataSourceProperties properties) {
return properties.initializeDataSourceBuilder().build();
}
}
}
4、使用JdbcTemplate操作数据库
SpringBoot中的 JdbcTemplate 是自动配置的，可以直接使用 @Autowired 或者 @Resource 来注入到需要的类中。
JdbcTemplateAutoConfiguration
@Configuration
@ConditionalOnClass({ DataSource.class, JdbcTemplate.class })
@ConditionalOnSingleCandidate(DataSource.class)
//在DataSourceAutoConfiguration自动配置类完成后再进行自动配置该类JdbcTemplateAutoConfiguration
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
public class JdbcTemplateAutoConfiguration {
private final DataSource dataSource;
public JdbcTemplateAutoConfiguration(DataSource dataSource) {
this.dataSource = dataSource;
}
//创建一个JdbcTemplate的Bean
@Bean
@Primary
@ConditionalOnMissingBean(JdbcOperations.class)
public JdbcTemplate jdbcTemplate() {
return new JdbcTemplate(this.dataSource);
}
@Bean
@Primary
@ConditionalOnMissingBean(NamedParameterJdbcOperations.class)
public NamedParameterJdbcTemplate namedParameterJdbcTemplate() {
return new NamedParameterJdbcTemplate(this.dataSource);
}
}
JdbcTemplateAutoConfiguration类中会创建一个JdbcTemplate的Bean，所以在使用的时候可以直接注入。
DataSourceAutoConfiguration
@Configuration
@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })
//启动DataSourceProperties配置类
@EnableConfigurationProperties(DataSourceProperties.class)
@Import({ Registrar.class, DataSourcePoolMetadataProvidersConfiguration.class })
public class DataSourceAutoConfiguration {
private static final Log logger = LogFactory
.getLog(DataSourceAutoConfiguration.class);
@Bean
@ConditionalOnMissingBean
public DataSourceInitializer dataSourceInitializer(DataSourceProperties properties,
ApplicationContext applicationContext) {
//根据配置文件属性创建DataSource的初始化器
return new DataSourceInitializer(properties, applicationContext);
}
//...
}
class DataSourceInitializer implements ApplicationListener<DataSourceInitializedEvent> {
private final DataSourceProperties properties;
private final ApplicationContext applicationContext;
private DataSource dataSource;
private boolean initialized = false;
DataSourceInitializer(DataSourceProperties properties,
ApplicationContext applicationContext) {
this.properties = properties;
this.applicationContext = applicationContext;
}
@PostConstruct
public void init() {
//当DataSourceProperties初始化完成后
if (!this.properties.isInitialize()) {
logger.debug("Initialization disabled (not running DDL scripts)");
return;
}
if (this.applicationContext.getBeanNamesForType(DataSource.class, false,
false).length > 0) {
//获取DataSource的bean
this.dataSource = this.applicationContext.getBean(DataSource.class);
}
if (this.dataSource == null) {
logger.debug("No DataSource found so not initializing");
return;
}
//...
}
}
JdbcTemplate操作数据库，就类似在Spring框架中使用JdbcTemplate一样，这里就不再累赘了。
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附上代码：
User实体类：
public class User implements Serializable {
private Integer uid;
private String uname;
private int uage;
//getter和setter
}
User控制器：
@RestController
@RequestMapping("/user")
public class UserController {
@Autowired
private IUserService userService;
@PostMapping("/")
public String insertUser(User user){
int count = userService.insertUser(user);
if(count != 1){
return "error";
}else{
return "success";
}
}
@GetMapping("/{uid}")
public User getUserById(@PathVariable Integer uid){
User user = userService.getUserById(uid);
return user;
}
@GetMapping("/")
public List<User> getAllUsers(){
return userService.getAllUsers();
}
@PutMapping("/{uid}")
public String updateUserById(@PathVariable Integer uid, User user){
return userService.updateUserById(uid, user) == 1 ? "success" : "error";
}
@DeleteMapping("/{uid}")
public String deleteUserById(@PathVariable Integer uid){
return userService.deleteUserById(uid) == 1 ? "success" : "error";
}
}
User业务层接口：
public interface IUserService {
int insertUser(User user);
User getUserById(Integer id);
List<User> getAllUsers();
int updateUserById(Integer uid, User user);
int deleteUserById(Integer uid);
}
User业务层接口实现类：
@Service
public class UserServiceImpl implements IUserService {
@Autowired
private IUserDao userDao;
@Override
public int insertUser(User user) {
return userDao.insertUser(user);
}
@Override
public User getUserById(Integer id) {
return userDao.getUserById(id);
}
@Override
public List<User> getAllUsers() {
return userDao.getAllUsers();
}
@Override
public int updateUserById(Integer uid, User user) {
return userDao.updateUserById(uid, user);
}
@Override
public int deleteUserById(Integer uid) {
return userDao.deleteUserById(uid);
}
}
User持久层接口：
public interface IUserDao {
int insertUser(User user);
User getUserById(Integer id);
List<User> getAllUsers();
int updateUserById(Integer uid, User user);
int deleteUserById(Integer uid);
}
User持久层接口实现类：
@Repository
public class UserDaoImpl implements IUserDao {
@Autowired
private JdbcTemplate jdbcTemplate;
@Override
public int insertUser(User user) {
return jdbcTemplate.update("insert into user values(null, ?, ?)", user.getUname(), user.getUage());
}
@Override
public User getUserById(Integer id) {
Object[] params = {id};
return jdbcTemplate.queryForObject("select * from user where uid=?", params, new UserRowMapper());
}
@Override
public List<User> getAllUsers() {
return jdbcTemplate.query("select * from user", new UserRowMapper());
}
@Override
public int updateUserById(Integer uid, User user) {
StringBuilder sb = new StringBuilder();
List<Object> params = new ArrayList<>();
boolean isUpdate = false;
if (user != null) {
sb.append("update user set ");
if (user.getUname() != null && !"".equals(StringUtils.trimWhitespace(user.getUname()))) {
isUpdate = true;
sb.append(" uname = ?,");
params.add(StringUtils.trimWhitespace(user.getUname()));
}
if (user.getUage() != 0) {
isUpdate = true;
sb.append(" uage = ?,");
params.add(user.getUage());
}
}
if (isUpdate) {
sb.deleteCharAt(sb.length() - 1);
sb.append(" where uid = ? ");
params.add(user.getUid());
return jdbcTemplate.update(sb.toString(), params.toArray());
} else {
return 0;
}
}
@Override
public int deleteUserById(Integer uid) {
return jdbcTemplate.update("delete from user where uid = ?", uid);
}
}
User数据映射类：
public class UserRowMapper implements RowMapper<User> {
@Override
public User mapRow(ResultSet resultSet, int i) throws SQLException {
User user = new User();
user.setUid(resultSet.getInt("uid"));
user.setUname(resultSet.getString("uname"));
user.setUage(resultSet.getInt("uage"));
return user;
}
}
本节使用Restful风格进行编写，大概知道Restful格式即可，此处不多讲述。
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