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.xmlsrc├───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>${spring-version}</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>exec-maven-plugin</artifactId> <version>1.6.0</version> <configuration> <mainClass>com.zetcode.Application</mainClass> </configuration> </plugin> </plugins> </build></project>
在pom.xml文件中，我们声明了基本的 Spring 依赖关系。 BeanPropertyRowMapper是spring-jdbc的一部分。
resources/db.properties
jdbc.driver=com.mysql.jdbc.Driverjdbc.url=jdbc:mysql://localhost:3306/mydbjdbc.username=user7jdbc.password=s$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:java12:47:37.079 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。
