Spring JdbcTemplate Abfragen von Beispielen

Beispiele für das Abfragen von Spring JdbcTemplate

Im Folgenden finden Sie einige Beispiele, die Ihnen zeigen, wie Sie mit SpringJdbcTemplate Daten aus der Datenbank abfragen oder extrahieren.

Verwendete Technologien:

Spring Boot 2.1.2.RELEASE
Spring JDBC 5.1.4.RELEASE
Maven 3
Java 8

Zusamenfassend:

jdbcTemplate.queryForObject für einzelne Zeile oder Wert
jdbcTemplate.query für mehrere Zeilen oder Listen

Note
Der Artikel wurde von Spring Core 2.5.x auf Spring Boot 2.1.x aktualisiert

P.S You may also interested in this Spring Boot JDBC Examples

1. Abfrage für einzelne Zeile

Im Frühjahr können wirjdbcTemplate.queryForObject() verwenden, um einen einzelnen Zeilendatensatz aus der Datenbank abzufragen und die Zeile über den Zeilen-Mapper in ein Objekt zu konvertieren.

1.1 Custom RowMapper

CustomerRowMapper.java

import org.springframework.jdbc.core.RowMapper;

import java.sql.ResultSet;
import java.sql.SQLException;

public class CustomerRowMapper implements RowMapper {

    @Override
    public Customer mapRow(ResultSet rs, int rowNum) throws SQLException {

        Customer customer = new Customer();
        customer.setID(rs.getLong("ID"));
        customer.setName(rs.getString("NAME"));
        customer.setAge(rs.getInt("AGE"));
        customer.setCreatedDate(rs.getTimestamp("created_date").toLocalDateTime());

        return customer;

    }
}

import org.springframework.jdbc.core.JdbcTemplate;

    @Autowired
    private JdbcTemplate jdbcTemplate;

    public Customer findByCustomerId(Long id) {

        String sql = "SELECT * FROM CUSTOMER WHERE ID = ?";

        return jdbcTemplate.queryForObject(sql, new Object[]{id}, new CustomerRowMapper());

    }

1.2 Spring BeanPropertyRowMapper, this class saves you a lot of time for the mapping.

import org.springframework.jdbc.core.BeanPropertyRowMapper;

    public Customer findByCustomerId2(Long id) {

        String sql = "SELECT * FROM CUSTOMER WHERE ID = ?";

        return (Customer) jdbcTemplate.queryForObject(
            sql,
            new Object[]{id},
            new BeanPropertyRowMapper(Customer.class));

    }

1.3 In Java 8, we can map it directly:

    public Customer findByCustomerId3(Long id) {

        String sql = "SELECT * FROM CUSTOMER WHERE ID = ?";

        return jdbcTemplate.queryForObject(sql, new Object[]{id}, (rs, rowNum) ->
                new Customer(
                        rs.getLong("id"),
                        rs.getString("name"),
                        rs.getInt("age"),
                        rs.getTimestamp("created_date").toLocalDateTime()
                ));

    }

2. Abfrage für mehrere Zeilen

Für mehrere Zeilen verwenden wirjdbcTemplate.query()

2.1 Custom RowMapper

    public List findAll() {

        String sql = "SELECT * FROM CUSTOMER";

        List customers = jdbcTemplate.query(
                sql,
                new CustomerRowMapper());

        return customers;

    }

2.2 BeanPropertyRowMapper

    public List findAll() {

        String sql = "SELECT * FROM CUSTOMER";

        List customers = jdbcTemplate.query(
                sql,
                new BeanPropertyRowMapper(Customer.class));

        return customers;
    }

2.3 Java 8

    public List findAll() {

        String sql = "SELECT * FROM CUSTOMER";

        return jdbcTemplate.query(
                sql,
                (rs, rowNum) ->
                        new Customer(
                                rs.getLong("id"),
                                rs.getString("name"),
                                rs.getInt("age"),
                                rs.getTimestamp("created_date").toLocalDateTime()
                        )
        );
    }

2.4 jdbcTemplate.queryForList, it works, but not recommend, the mapping in Map may not same as the object, need casting.

    public List findAll() {

        String sql = "SELECT * FROM CUSTOMER";

        List customers = new ArrayList<>();

        List> rows = jdbcTemplate.queryForList(sql);

        for (Map row : rows) {
            Customer obj = new Customer();

            obj.setID(((Integer) row.get("ID")).longValue());
            obj.setName((String) row.get("NAME"));
            // Spring returns BigDecimal, need convert
            obj.setAge(((BigDecimal) row.get("AGE")).intValue());
            obj.setCreatedDate(((Timestamp) row.get("CREATED_DATE")).toLocalDateTime());
            customers.add(obj);
        }

        return customers;
    }

3. Abfrage für einen einzelnen Wert

Es ist dasselbe wie beim Abfragen einer einzelnen Zeile aus der Datenbank, wobeijdbcTemplate.queryForObject() verwendet werden

3.1 Single column name

    public String findCustomerNameById(Long id) {

        String sql = "SELECT NAME FROM CUSTOMER WHERE ID = ?";

        return jdbcTemplate.queryForObject(
                sql, new Object[]{id}, String.class);

    }

3.2 Count

    public int count() {

        String sql = "SELECT COUNT(*) FROM CUSTOMER";

        // queryForInt() is Deprecated
        // https://www.example.com/spring/jdbctemplate-queryforint-is-deprecated/
        //int total = jdbcTemplate.queryForInt(sql);

        return jdbcTemplate.queryForObject(sql, Integer.class);

    }

4. Test

Führen Sie die Anwendung Spring BootCommandLineRunneraus, erstellen Sie Tabellen und testen Sie die APIs.

pom.xml

    
        org.springframework.boot
        spring-boot-starter-jdbc
    

    
    
        com.h2database
        h2

StartApplication.java

package com.example;

import com.example.customer.Customer;
import com.example.customer.CustomerRepository;

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;

import java.math.BigDecimal;
import java.util.Arrays;
import java.util.List;

@SpringBootApplication
public class StartApplication implements CommandLineRunner {

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

    @Autowired
    JdbcTemplate jdbcTemplate;

    @Autowired
    CustomerRepository customerRepository;

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

    @Override
    public void run(String... args) {

        log.info("StartApplication...");

        startCustomerApp();

    }

    // Tested with H2 database
    void startCustomerApp() {

        jdbcTemplate.execute("DROP TABLE customer IF EXISTS");
        jdbcTemplate.execute("CREATE TABLE customer(" +
                "id SERIAL, name VARCHAR(255), age NUMERIC(2), created_date timestamp)");

        List list = Arrays.asList(
                new Customer("Customer A", 19),
                new Customer("Customer B", 20),
                new Customer("Customer C", 21),
                new Customer("Customer D", 22)
        );

        list.forEach(x -> {
            log.info("Saving...{}", x.getName());
            customerRepository.save(x);
        });

        log.info("[FIND_BY_ID]");
        log.info("{}", customerRepository.findByCustomerId(1L));
        log.info("{}", customerRepository.findByCustomerId2(2L));
        log.info("{}", customerRepository.findByCustomerId3(3L));

        log.info("[FIND_ALL]");
        log.info("{}", customerRepository.findAll());
        log.info("{}", customerRepository.findAll2());
        log.info("{}", customerRepository.findAll3());
        log.info("{}", customerRepository.findAll4());

        log.info("[FIND_NAME_BY_ID]");
        log.info("{}", customerRepository.findCustomerNameById(4L));

        log.info("[COUNT]");
        log.info("{}", customerRepository.count());

    }

}

Ausgabe

INFO  com.example.StartApplication - Saving...Customer A
INFO  com.example.StartApplication - Saving...Customer B
INFO  com.example.StartApplication - Saving...Customer C
INFO  com.example.StartApplication - Saving...Customer D
INFO  com.example.StartApplication - [FIND_BY_ID]
INFO  com.example.StartApplication - Customer{ID=1, name='Customer A', age=19, createdDate=2019-08-01T15:48:45.950848}
INFO  com.example.StartApplication - Customer{ID=2, name='Customer B', age=20, createdDate=2019-08-01T15:48:45.961819}
INFO  com.example.StartApplication - Customer{ID=3, name='Customer C', age=21, createdDate=2019-08-01T15:48:45.961819}
INFO  com.example.StartApplication - [FIND_ALL]
INFO  com.example.StartApplication - [
    Customer{ID=1, name='Customer A', age=19, createdDate=2019-08-01T15:48:45.950848},
    Customer{ID=2, name='Customer B', age=20, createdDate=2019-08-01T15:48:45.961819},
    Customer{ID=3, name='Customer C', age=21, createdDate=2019-08-01T15:48:45.961819},
    Customer{ID=4, name='Customer D', age=22, createdDate=2019-08-01T15:48:45.961819}
    ]
//...omitted, duplicate code
INFO  com.example.StartApplication - [FIND_NAME_BY_ID]
INFO  com.example.StartApplication - Customer D
INFO  com.example.StartApplication - [COUNT]
INFO  com.example.StartApplication - 4

Quellcode herunterladen

$ git clone https://github.com/example/spring-boot.git
$ cd spring-jdbc
$ find com.example.customer

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