极客教程Spring BeanPropertyRowMapper 教程展示了如何使用 BeanPropertyRowMapper 将表行转换为指定 Bean 类的新实例。
Spring 是用于创建企业应用的流行 Java 应用框架。
Spring BeanPropertyRowMapper
BeanPropertyRowMapper是RowMapper执行该表的行转换成指定的映射的目标类的一个新实例。 映射的目标类必须是顶级类，并且必须具有默认或无参数构造函数。
Spring BeanPropertyRowMapper示例
以下应用使用BeanPropertyRowMapper从coutries表中读取所有行。 在示例中，我们使用 MySQL 数据库。
countries.sql
CREATE TABLE countries(id INT PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(255), population INT);
INSERT INTO countries(name, population) VALUES('China', 1382050000);
INSERT INTO countries(name, population) VALUES('India', 1313210000);
INSERT INTO countries(name, population) VALUES('USA', 324666000);
INSERT INTO countries(name, population) VALUES('Indonesia', 260581000);
INSERT INTO countries(name, population) VALUES('Brazil', 207221000);
INSERT INTO countries(name, population) VALUES('Pakistan', 196626000);
INSERT INTO countries(name, population) VALUES('Nigeria', 186988000);
INSERT INTO countries(name, population) VALUES('Bangladesh', 162099000);
INSERT INTO countries(name, population) VALUES('Nigeria', 186988000);
INSERT INTO countries(name, population) VALUES('Russia', 146838000);
INSERT INTO countries(name, population) VALUES('Japan', 126830000);
INSERT INTO countries(name, population) VALUES('Mexico', 122273000);
INSERT INTO countries(name, population) VALUES('Philippines', 103738000);
这是我们示例的一些测试数据。
pom.xml
src
├───main
│ ├───java
│ │ └───com
│ │ └───zetcode
│ │ │ Application.java
│ │ ├───config
│ │ │ DBConfig.java
│ │ └───model
│ │ Country.java
│ └───resources
│ db.properties
│ logback.xml
└───test
└───java
这是项目结构。
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.zetcode</groupId>
<artifactId>springbeanpropertyrowmapperex</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
<spring-version>5.1.3.RELEASE</spring-version>
</properties>
<dependencies>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>{spring-version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>{spring-version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring-version}</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.6.0</version>
<configuration>
<mainClass>com.zetcode.Application</mainClass>
</configuration>
</plugin>
</plugins>
</build>
</project>
在pom.xml文件中，我们声明了基本的 Spring 依赖关系。 BeanPropertyRowMapper是spring-jdbc的一部分。
resources/db.properties
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mydb
jdbc.username=user7
jdbc.password=s$cret
我们在外部文件中具有基本的数据库属性。
resources/logback.xml
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<logger name="org.springframework" level="ERROR"/>
<logger name="com.zetcode" level="INFO"/>
<appender name="consoleAppender" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<Pattern>%d{HH:mm:ss.SSS} [%thread] %blue(%-5level) %magenta(%logger{36}) - %msg %n
</Pattern>
</encoder>
</appender>
<root>
<level value="INFO" />
<appender-ref ref="consoleAppender" />
</root>
</configuration>
logback.xml是 Logback 日志库的配置文件。
com/zetcode/model/Country.java
package com.zetcode.model;
import java.util.Objects;
public class Country {
private Long id;
private String name;
private int population;
public Country() {
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = 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 boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Country country = (Country) o;
return population == country.population &&
Objects.equals(id, country.id) &&
Objects.equals(name, country.name);
}
@Override
public int hashCode() {
return Objects.hash(id, name, population);
}
@Override
public String toString() {
final StringBuilder sb = new StringBuilder("Country{");
sb.append("id=").append(id);
sb.append(", name='").append(name).append('\'');
sb.append(", population=").append(population);
sb.append('}');
return sb.toString();
}
}
这是Country bean。 它具有id，name和population属性。
com/zetcode/config/DBConfig.java
package com.zetcode.config;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import javax.sql.DataSource;
@Configuration
@PropertySource(value="classpath:db.properties", ignoreResourceNotFound=true)
public class DBConfig {
@Autowired
private Environment env;
@Bean
public DataSource dataSource() {
var dataSource = new DriverManagerDataSource();
dataSource.setDriverClassName(env.getProperty("jdbc.driver"));
dataSource.setUrl(env.getProperty("jdbc.url"));
dataSource.setUsername(env.getProperty("jdbc.username"));
dataSource.setPassword(env.getProperty("jdbc.password"));
return dataSource;
}
@Bean
public JdbcTemplate jdbcTemplate() {
var template = new JdbcTemplate();
template.setDataSource(dataSource());
return template;
}
}
DBConfig配置dataSource和jdbcTemplate bean。 它从db.properties文件读取配置数据。
com/zetcode/Application.java
package com.zetcode;
import com.zetcode.model.Country;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
@ComponentScan("com.zetcode")
public class Application {
private static final Logger logger = LoggerFactory.getLogger(Application.class);
public static void main(String[] args) {
var ctx = new AnnotationConfigApplicationContext(Application.class);
var app = ctx.getBean(Application.class);
app.run();
ctx.close();
}
@Autowired
private JdbcTemplate jdbcTemplate;
private void run() {
var sql = "SELECT * FROM countries";
var rowMapper = BeanPropertyRowMapper.newInstance(Country.class);
var countries = jdbcTemplate.query(sql, rowMapper);
countries.forEach(country -> logger.info("{}", country));
}
}
这是主要的应用类。
var sql = "SELECT * FROM countries";
我们定义一个查询以从countries表中检索所有行。
var rowMapper = BeanPropertyRowMapper.newInstance(Country.class);
我们为Country类创建BeanPropertyRowMapper的新实例。
var countries = jdbcTemplate.query(sql, rowMapper);
JdbcTemplate 的query()执行 SQL 查询。 由于BeanPropertyRowMapper，表列自动映射到 bean 属性。
$ mvn -q exec:java
12:47:37.079 INFO com.zetcode.Application - Country{id=1, name='China', population=1382050000}
12:47:37.082 INFO com.zetcode.Application - Country{id=2, name='India', population=1313210000}
12:47:37.083 INFO com.zetcode.Application - Country{id=3, name='USA', population=324666000}
12:47:37.084 INFO com.zetcode.Application - Country{id=4, name='Indonesia', population=260581000}
12:47:37.084 INFO com.zetcode.Application - Country{id=5, name='Brazil', population=207221000}
12:47:37.085 INFO com.zetcode.Application - Country{id=6, name='Pakistan', population=196626000}
12:47:37.086 INFO com.zetcode.Application - Country{id=7, name='Nigeria', population=186988000}
12:47:37.087 INFO com.zetcode.Application - Country{id=8, name='Bangladesh', population=162099000}
12:47:37.088 INFO com.zetcode.Application - Country{id=9, name='Nigeria', population=186988000}
12:47:37.088 INFO com.zetcode.Application - Country{id=10, name='Russia', population=146838000}
12:47:37.089 INFO com.zetcode.Application - Country{id=11, name='Japan', population=126830000}
12:47:37.090 INFO com.zetcode.Application - Country{id=12, name='Mexico', population=122273000}
12:47:37.090 INFO com.zetcode.Application - Country{id=13, name='Philippines', population=103738000}
我们运行该应用。
在本教程中，我们使用BeanPropertyRowMapper将表行映射到 bean 属性。