SpringBoot之Access Relational Data

使用org.springframework.jdbc.core.JdbcTemplate对数据库进行操作。

程序主要代码：

package access.relational.data;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.jdbc.core.JdbcTemplate;

@SpringBootApplication
public class Application implements CommandLineRunner {

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

    @Autowired
    JdbcTemplate jdbcTemplate;

    @Override
    public void run(String... arg0) throws Exception {
        log.info("Creating tables");

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

        // Split up the array of whole names into an array of first/last names
        List<Object[]> splitUpNames = Arrays.asList("John Woo", "Jeff Dean", "Josh Bloch", "Josh Long").stream()
                .map(name -> name.split(" "))
                .collect(Collectors.toList());

        // Use a Java 8 stream to print out each tuple of the list
        splitUpNames.forEach(name -> log.info(String.format("Inserting customer record for %s %s", name[0], name[1])));

        // Uses JdbcTemplate's batchUpdate operation to bulk load data
        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()));
    }

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

}

说明：

The main() method uses Spring Boot’s SpringApplication.run() method to launch an application. Did you notice that there wasn’t a single line of XML? No web.xml file either. This web application is 100% pure Java and you didn’t have to deal with configuring any plumbing or infrastructure.

Spring Boot spots H2, an in-memory relational database engine, and automatically creates a connection. Because we are using spring-jdbc, Spring Boot automatically creates a JdbcTemplate. The @Autowired JdbcTemplate field automatically loads it and makes it available.

This Application class implements Spring Boot’s CommandLineRunner, which means it will execute the run() method after the application context is loaded up.

org.springframework.jdbc.core.JdbcTemplate