Spring JDBC RowMapper接口示例

JdbcTemplate類使用org.springframework.jdbc.core.RowMapper <T>接口在每行的基礎上映射ResultSet的行。該接口的實現執行將每行映射到結果對象的實際工作。如果拋出SQLExceptions將被調用的JdbcTemplate捕獲和處理。

接口的聲明

以下是org.springframework.jdbc.core.RowMapper<T>接口的聲明 -

public interface RowMapper<T>

用法

步驟1 - 使用配置的數據源創建一個JdbcTemplate對象。
步驟2 - 創建一個實現RowMapper接口的StudentMapper對象。
步驟3 - 使用JdbcTemplate對象方法在使用StudentMapper對象時進行數據庫操作。

實例

以下示例將演示如何使用spring jdbc進行讀取查詢。使用StudentMapper對象將讀取記錄從student表映射到Student對象。

語法

String SQL = "select * from Student";
List <Student> students = jdbcTemplateObject.query(SQL, 
   new StudentMapper());

在上面示例(語法)代碼中 -

  • SQL - 選擇查詢語句來來讀取學生記錄信息。
  • jdbcTemplateObject - StudentJDBCTemplate對象從數據庫中讀取Student對象。
  • StudentMapper - StudentMapper對象將學生記錄映射到Student對象。

實例項目

要了解上述與Spring JDBC相關的概念,下面我們編寫一個使用Mapper對象來讀取查詢並映射結果到Student對象。打開Eclipse IDE,並按照以下步驟創建一個Spring應用程序,這裏創建一個名稱爲:RowMapper 的項目。

步驟說明

  1. 參考第一個Spring JDBC項目來創建一個Maven項目 - http://www.yiibai.com/springjdbc/first\_application.html
  2. 更新bean配置並運行應用程序。

完整的項目結構如下所示 -

Spring

以下是Maven配置文件:pom.xml的代碼內容:

<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.yiibai</groupId>
    <artifactId>RowMapper</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>RowMapper</name>
    <url>http://maven.apache.org</url>
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.40</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>4.1.0.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.1.4.RELEASE</version>
        </dependency>
    </dependencies>
</project>

以下是數據訪問對象接口文件:StudentDAO.java的內容:

package com.yiibai;

import java.util.List;
import javax.sql.DataSource;

public interface StudentDAO {
    /**
     * This is the method to be used to initialize database resources ie.
     * connection.
     */
    public void setDataSource(DataSource ds);

    /**
     * This is the method to be used to list down all the records from the
     * Student table.
     */
    public List<Student> listStudents();
    public Student getStudent(Integer id);
    public void create(String name, Integer age);
}

以下是文件:Student.java的代碼內容:

package com.yiibai;

public class Student {
    private Integer age;
    private String name;
    private Integer id;

    public void setAge(Integer age) {
        this.age = age;
    }

    public Integer getAge() {
        return age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getId() {
        return id;
    }
}

以下是文件:StudentMapper.java的代碼內容:

package com.yiibai;

import java.sql.ResultSet;
import java.sql.SQLException;
import org.springframework.jdbc.core.RowMapper;

public class StudentMapper implements RowMapper<Student> {
    public Student mapRow(ResultSet rs, int rowNum) throws SQLException {
        Student student = new Student();
        student.setId(rs.getInt("id"));
        student.setName(rs.getString("name"));
        student.setAge(rs.getInt("age"));
        return student;
    }
}

實現類StudentJDBCTemplate.java實現了定義的DAO接口 - StudentDAO.java,以下是文件:StudentJDBCTemplate.java的代碼內容:

package com.yiibai;

import java.util.List;
import java.util.ArrayList;
import javax.sql.DataSource;

import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.PreparedStatementSetter;
import org.springframework.jdbc.core.ResultSetExtractor;

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

public class StudentJDBCTemplate implements StudentDAO {
    private DataSource dataSource;
    private JdbcTemplate jdbcTemplateObject;

    public void setDataSource(DataSource dataSource) {
        this.dataSource = dataSource;
        this.jdbcTemplateObject = new JdbcTemplate(dataSource);
    }

    public List<Student> listStudents() {
        String SQL = "select * from Student";
        List<Student> students = jdbcTemplateObject.query(SQL, new StudentMapper());
        return students;
    }

    public void create(String name, Integer age) {
        // TODO Auto-generated method stub
        String insertQuery = "insert into student (name, age) values (?, ?)";

        jdbcTemplateObject.update(insertQuery, name, age);
        System.out.println("Created Record Name = " + name + " Age = " + age);
        return;
    }

    public Student getStudent(final Integer id) {
        final String SQL = "select * from Student where id = ? ";
        List<Student> students = jdbcTemplateObject.query(SQL, new PreparedStatementSetter() {
            public void setValues(PreparedStatement preparedStatement) throws SQLException {
                preparedStatement.setInt(1, id);
            }
        }, new StudentMapper());
        return students.get(0);
    }
}

以下是文件:MainApp.java的代碼內容:

package com.yiibai;

import java.util.ArrayList;
import java.util.List;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.yiibai.StudentJDBCTemplate;

public class MainApp {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("application-beans.xml");

        StudentJDBCTemplate studentJDBCTemplate = (StudentJDBCTemplate) context.getBean("studentJDBCTemplate");

        System.out.println("------Records Creation--------");
        studentJDBCTemplate.create("Maxsu", 21);
        studentJDBCTemplate.create("Curry", 22);
        studentJDBCTemplate.create("Suzend", 23);

        System.out.println("------Listing Multiple Records--------");
        List<Student> students = studentJDBCTemplate.listStudents();
        for (Student record : students) {
            System.out.print("ID : " + record.getId());
            System.out.print(", Name : " + record.getName());
            System.out.println(", Age : " + record.getAge());
        }
    }
}

以下是文件:application-beans.xml的代碼內容:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd ">

    <!-- Initialization for data source -->
    <bean id="dataSource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost:3306/test?characterEncoding=utf8&useSSL=true" />
        <property name="username" value="root" />
        <property name="password" value="123456" />
    </bean>

    <!-- Definition for studentJDBCTemplate bean -->
    <bean id="studentJDBCTemplate" class="com.yiibai.StudentJDBCTemplate">
        <property name="dataSource" ref="dataSource" />
    </bean>

</beans>

注意: application-beans.xml 文件的位置是:{workspace}/fistapp/src/main/java 目錄,如果放置錯了,程序可能會因爲找不到此配置文件而出錯。

完成創建源代碼和bean和數據庫連接信息的文件配置後,運行應用程序。這裏先簡單說明一下運行的步驟,在項目名稱(RowMapper)上點擊右鍵,在彈出的菜單中選擇:【Run As】-> 【Maven test】

在運行測試成功後,應該會輸出類似以下內容(含有 BUILD SUCCESS 的信息) 。
接下來,點擊類文件:MainApp.java 選擇【Run As】->【Java Application】,如果應用程序一切正常,這將打印以下結果:

------Records Creation--------
Created Record Name = Maxsu Age = 21
Created Record Name = Curry Age = 22
Created Record Name = Suzend Age = 23
------Listing Multiple Records--------
ID : 1, Name : Maxsu, Age : 21
ID : 2, Name : Curry, Age : 22
ID : 3, Name : Suzend, Age : 23