SpringBoot——使用Spring和JDBC访问关系型数据

创建一个Customer类

public class Customer {
    private long id;
    private String firstName, lastName;

    public Customer(long id, String firstName, String lastName) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getFirstName() {
        return firstName;
    }

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

    public String getLastName() {
        return lastName;
    }

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

    @Override
    public String toString() {
        return     String.format("Customer[id=%d,firstName='%s',lastName='%s'", id, firstName, lastName);
    }
}

存储和检索数据

Spring提供了一个名为JdbcTemplate的模板类。

  @SpringBootApplication
public class Application implements CommandLineRunner {

private static final Logger log = LoggerFactory.getLogger(Application.class);

public static void main(String[] args) {
    SpringApplication.run(Application.class);
}

@Autowired
JdbcTemplate jdbcTemplate;

@Override
public void run(String... strings) throws Exception {
    log.info("Createing tables");

    jdbcTemplate.execute("DROP TABLE customers IF EXISTS ");
    jdbcTemplate.execute("CREATE TABLE customers(" +
            "id SERIAL, first_name VARCHAR(255), last_name VARCHAR(255))");

    List<Object[]> splitUpNames = Arrays.asList("John Woo", "Jeff Dean", "Josh Bloch", "Josh Long").stream()
            .map(name -> name.split(" ")).collect(Collectors.toList());

    splitUpNames.forEach(name -> log.info(String.format("Inserting customer record for %s %s", name[0], name[1])));

    jdbcTemplate.batchUpdate("INSERT INTO customers(first_name, last_name) VALUES (?,?)", splitUpNames);
    log.info("Querying for customer records where first_name = 'Josh':");

    jdbcTemplate.query(
            "SELECT id, first_name, last_name FROM customers WHERE first_name = ?", new Object[]{"Josh"},
            (rs, rowNum) -> new Customer(rs.getLong("id"), rs.getString("first_name"), rs.getString("last_name"))
    ).forEach(customer -> log.info(customer.toString()));
    }
}

Spring Boot支持H2（一种内存中的关系数据库引擎），并自动创建一个连接。因为我们使用的是spring-jdbc，Spring Boot会自动创建一个JdbcTemplate。@Autowired JdbcTemplate字段会自动加载它并使其可用。

这个Application类实现了Spring Boot的CommandLineRunner，这意味着它将在应用程序上下文加载完成后执行run（）方法。