Spring Boot BeanPropertyRowMapper
最后修改于 2023 年 7 月 24 日
在本文中，我们将展示如何使用 BeanPropertyRowMapper 将表行转换为指定 Bean 类的新实例。
Spring Boot 是一个流行的应用程序框架，用于在 Java、Kotlin 或 Groovy 中创建企业应用程序。
BeanPropertyRowMapper
BeanPropertyRowMapper 是一个 RowMapper 实现，它将表行转换为指定映射目标类的新实例。 映射目标类必须是顶级类，并且它必须具有默认的或无参数构造函数。
Spring Boot BeanPropertyRowMapper 示例
以下应用程序使用 BeanPropertyRowMapper 将结果集行映射到 City Bean。
build.gradle
...
src
├───main
│ ├───java
│ │ └───com
│ │ └───zetcode
│ │ │ Application.java
│ │ │ MyRunner.java
│ │ ├───model
│ │ │ City.java
│ │ └───service
│ │ CityService.java
│ │ ICityService.java
│ └───resources
│ application.properties
│ data-h2.sql
│ schema-h2.sql
└───test
└───java
这是 Spring Boot 应用程序的项目结构。
build.gradle
plugins {
id 'org.springframework.boot' version '3.1.1'
id 'io.spring.dependency-management' version '1.1.0'
id 'java'
}
group = 'com.zetcode'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'
repositories {
mavenCentral()
}
dependencies {
implementation 'org.springframework.boot:spring-boot-starter-jdbc'
runtimeOnly 'com.h2database:h2'
}
这是 Gradle 构建文件。 RowMapper 位于 spring-boot-starter-jdbc 依赖项中。 我们将数据存储在 H2 数据库中。
resources/application.properties
spring.main.banner-mode=off # spring.datasource.platform=h2 deprecated spring.sql.init.platform=h2 spring.datasource.driverClassName=org.h2.Driver spring.datasource.url=jdbc:h2:mem:testdb
在 application.properties 中，我们关闭 Spring Boot 标语并设置 H2 数据源。
resources/schema-h2.sql
CREATE TABLE cities(id BIGINT PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(255), population BIGINT);
此 SQL 脚本创建城市表。
resources/data-h2.sql
INSERT INTO cities(name, population) VALUES('Bratislava', 432000);
INSERT INTO cities(name, population) VALUES('Budapest', 1759000);
INSERT INTO cities(name, population) VALUES('Prague', 1280000);
INSERT INTO cities(name, population) VALUES('Warsaw', 1748000);
INSERT INTO cities(name, population) VALUES('Los Angeles', 3971000);
INSERT INTO cities(name, population) VALUES('New York', 8550000);
INSERT INTO cities(name, population) VALUES('Edinburgh', 464000);
INSERT INTO cities(name, population) VALUES('Berlin', 3671000);
SQL 脚本用数据填充表。
com/zetcode/model/City.java
package com.zetcode.model;
import java.util.Objects;
public class City {
private Long id;
private String name;
private int population;
public City() {
}
public City(Long id, String name, int population) {
this.id = id;
this.name = name;
this.population = population;
}
public Long getId() {
return id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getPopulation() {
return population;
}
public void setPopulation(int population) {
this.population = population;
}
@Override
public int hashCode() {
int hash = 7;
hash = 79 * hash + Objects.hashCode(this.id);
hash = 79 * hash + Objects.hashCode(this.name);
hash = 79 * hash + this.population;
return hash;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
final City other = (City) obj;
if (this.population != other.population) {
return false;
}
if (!Objects.equals(this.name, other.name)) {
return false;
}
return Objects.equals(this.id, other.id);
}
@Override
public String toString() {
final StringBuilder sb = new StringBuilder("City{");
sb.append("id=").append(id);
sb.append(", name='").append(name).append('\'');
sb.append(", population=").append(population);
sb.append('}');
return sb.toString();
}
}
这是 City 模型类。
com/zetcode/service/ICityService.java
package com.zetcode.service;
import com.zetcode.model.City;
import java.util.List;
public interface ICityService {
List<City> findAll();
City findById(Long id);
}
在 ICityService 中有两个契约方法。
com/zetcode/service/CityService.java
package com.zetcode.service;
import com.zetcode.model.City;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;
import java.util.List;
@Service
public class CityService implements ICityService {
private final JdbcTemplate jtm;
public CityService(JdbcTemplate jtm) {
this.jtm = jtm;
}
@Override
public List<City> findAll() {
String sql = "SELECT * FROM cities";
return jtm.query(sql, BeanPropertyRowMapper.newInstance(City.class));
}
@Override
public City findById(Long id) {
String sql = "SELECT * FROM cities WHERE id = ?";
return jtm.queryForObject(sql,
BeanPropertyRowMapper.newInstance(City.class), id);
}
}
我们有两个契约方法的实现，使用 BeanPropertyRowMapper。 列值基于将从结果集元数据获取的列名与相应属性的公共 setter 进行匹配来映射。
com/zetcode/MyRunner.java
package com.zetcode;
import com.zetcode.service.ICityService;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
@Component
public class MyRunner implements CommandLineRunner {
private final ICityService cityService;
public MyRunner(ICityService cityService) {
this.cityService = cityService;
}
@Override
public void run(String... args) throws Exception {
var city = cityService.findById(1L);
System.out.println(city);
var data = cityService.findAll();
System.out.println(data);
}
}
在 MyRunner 中，我们通过其 Id 查找一个城市，然后查找所有城市。
com/zetcode/Application.java
package com.zetcode;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
`Application` 设置了 Spring Boot 应用程序。
$ ./gradlew bootRun
...
City{id=null, name='Bratislava', population=432000}
[City{id=null, name='Bratislava', population=432000},
City{id=null, name='Budapest', population=1759000},
City{id=null, name='Prague', population=1280000},
City{id=null, name='Warsaw', population=1748000},
City{id=null, name='Los Angeles', population=3971000},
City{id=null, name='New York', population=8550000},
City{id=null, name='Edinburgh', population=464000},
City{id=null, name='Berlin', population=3671000}]
...
在本文中，我们使用了 Spring Boot BeanPropertyRowMapper。