Spring4 之 JdbcTemplate

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Spring4 之 JdbcTemplate

为了使 JDBC 更加易于使用, Spring 在 JDBC API 上定义了一个抽象层, 以此建立一个 JDBC 存取框架。

作为 Spring JDBC 框架的核心, JDBC 模板的设计目的是为不同类型的 JDBC 操作提供模板方法. 每个模板方法都能控制整个过程, 并允许覆盖过程中的特定任务. 通过这种方式, 可以在尽可能保留灵活性的情况下, 将数据库存取的工作量降到最低。

实例

延用之前的项目框架

添加Spring JDBC 相关的 jar包

        <!-- Spring JDBC starts -->        <!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->        <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-jdbc</artifactId>            <version>4.3.7.RELEASE</version>        </dependency>        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>            <version>5.1.6</version>        </dependency>        <!-- https://mvnrepository.com/artifact/c3p0/c3p0 -->        <dependency>            <groupId>c3p0</groupId>            <artifactId>c3p0</artifactId>            <version>0.9.1.2</version>        </dependency>        <!-- Spring JDBC ends -->

java 部分代码

Department.java

package com.spring.example.jdbc;public class Department {    private Integer id;    private String name;    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    public String toString() {        return "Department [id=" + id + ", name=" + name + "]";    }}

DepartmentDao.java

package com.spring.example.jdbc;import javax.sql.DataSource;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.jdbc.core.BeanPropertyRowMapper;import org.springframework.jdbc.core.RowMapper;import org.springframework.jdbc.core.support.JdbcDaoSupport;import org.springframework.stereotype.Repository;@Repository("departmentDao")public class DepartmentDao extends JdbcDaoSupport{    @Autowired    public void setDataSource2(DataSource dataSource){        setDataSource(dataSource);    }    public Department get(Integer id){        String sql = "SELECT id, dept_name name FROM departments WHERE id = ?";        RowMapper<Department> rowMapper = new BeanPropertyRowMapper<>(Department.class);        return getJdbcTemplate().queryForObject(sql, rowMapper, id);    }}

Employee.java

package com.spring.example.jdbc;public class Employee {    private Integer id;    private String lastName;    private String email;    private Integer dpetId;    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getLastName() {        return lastName;    }    public void setLastName(String lastName) {        this.lastName = lastName;    }    public String getEmail() {        return email;    }    public void setEmail(String email) {        this.email = email;    }    public Integer getDpetId() {        return dpetId;    }    public void setDpetId(Integer dpetId) {        this.dpetId = dpetId;    }    @Override    public String toString() {        return "Employee [id=" + id + ", lastName=" + lastName + ", email="                + email + ", dpetId=" + dpetId + "]";    }}

EmployeeDao.java

package com.spring.example.jdbc;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.jdbc.core.BeanPropertyRowMapper;import org.springframework.jdbc.core.JdbcTemplate;import org.springframework.jdbc.core.RowMapper;import org.springframework.stereotype.Repository;@Repository("employeeDao")public class EmployeeDao {    @Autowired    private JdbcTemplate jdbcTemplate;    public Employee get(Integer id){        String sql = "SELECT id, last_name lastName, email FROM employees WHERE id = ?";        RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);        Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, id);        return employee;    }}

JDBCTest.java

package com.spring.example.jdbc;import java.sql.SQLException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import javax.sql.DataSource;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import org.springframework.jdbc.core.BeanPropertyRowMapper;import org.springframework.jdbc.core.JdbcTemplate;import org.springframework.jdbc.core.RowMapper;import org.springframework.jdbc.core.namedparam.BeanPropertySqlParameterSource;import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;import org.springframework.jdbc.core.namedparam.SqlParameterSource;public class JDBCTest {    private ApplicationContext ctx = null;    private JdbcTemplate jdbcTemplate;    private EmployeeDao employeeDao;    private DepartmentDao departmentDao;    private NamedParameterJdbcTemplate namedParameterJdbcTemplate;    {        ctx = new ClassPathXmlApplicationContext("applicationContext.xml");        jdbcTemplate = (JdbcTemplate) ctx.getBean("jdbcTemplate");        employeeDao = ctx.getBean(EmployeeDao.class);        departmentDao = ctx.getBean(DepartmentDao.class);        namedParameterJdbcTemplate = ctx.getBean(NamedParameterJdbcTemplate.class);    }    /**     * 使用具名参数时, 可以使用 update(String sql, SqlParameterSource paramSource) 方法进行更新操作     * 1. SQL 语句中的参数名和类的属性一致!     * 2. 使用 SqlParameterSource 的 BeanPropertySqlParameterSource 实现类作为参数.      */    @Test    public void testNamedParameterJdbcTemplate2(){        String sql = "INSERT INTO employees(last_name, email, dept_id) "                + "VALUES(:lastName,:email,:dpetId)";        Employee employee = new Employee();        employee.setLastName("XYZ");        employee.setEmail("xyz@sina.com");        employee.setDpetId(3);        SqlParameterSource paramSource = new BeanPropertySqlParameterSource(employee);        namedParameterJdbcTemplate.update(sql, paramSource);    }    /**     * 可以为参数起名字.      * 1. 好处: 若有多个参数, 则不用再去对应位置, 直接对应参数名, 便于维护     * 2. 缺点: 较为麻烦.      */    @Test    public void testNamedParameterJdbcTemplate(){        String sql = "INSERT INTO employees(last_name, email, dept_id) VALUES(:ln,:email,:deptid)";        Map<String, Object> paramMap = new HashMap<>();        paramMap.put("ln", "FF");        paramMap.put("email", "ff@163.com");        paramMap.put("deptid", 2);        namedParameterJdbcTemplate.update(sql, paramMap);    }    @Test    public void testDepartmentDao(){        System.out.println(departmentDao.get(1));    }    @Test    public void testEmployeeDao(){        System.out.println(employeeDao.get(1));    }    /**     * 获取单个列的值, 或做统计查询     * 使用 queryForObject(String sql, Class<Long> requiredType)      */    @Test    public void testQueryForObject2(){        String sql = "SELECT count(id) FROM employees";        long count = jdbcTemplate.queryForObject(sql, Long.class);        System.out.println(count);    }    /**     * 查到实体类的集合     * 注意调用的不是 queryForList 方法     */    @Test    public void testQueryForList(){        String sql = "SELECT id, last_name lastName, email FROM employees WHERE id > ?";        RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);        List<Employee> employees = jdbcTemplate.query(sql, rowMapper,5);        System.out.println(employees);    }    /**     * 从数据库中获取一条记录, 实际得到对应的一个对象     * 注意不是调用 queryForObject(String sql, Class<Employee> requiredType, Object... args) 方法!     * 而需要调用 queryForObject(String sql, RowMapper<Employee> rowMapper, Object... args)     * 1. 其中的 RowMapper 指定如何去映射结果集的行, 常用的实现类为 BeanPropertyRowMapper     * 2. 使用 SQL 中列的别名完成列名和类的属性名的映射. 例如 last_name lastName     * 3. 不支持级联属性. JdbcTemplate 到底是一个 JDBC 的小工具, 而不是 ORM 框架     */    @Test    public void testQueryForObject(){        String sql = "SELECT id, last_name lastName, email, dept_id as \"department.id\" FROM employees WHERE id = ?";        RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<>(Employee.class);        Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, 1);        System.out.println(employee);    }    /**     * 执行批量更新: 批量的 INSERT, UPDATE, DELETE     * 最后一个参数是 Object[] 的 List 类型: 因为修改一条记录需要一个 Object 的数组, 那么多条不就需要多个 Object 的数组吗     */    @Test    public void testBatchUpdate(){        String sql = "INSERT INTO employees(last_name, email, dept_id) VALUES(?,?,?)";        List<Object[]> batchArgs = new ArrayList<>();        batchArgs.add(new Object[]{"AA", "aa@163.com", 1});        batchArgs.add(new Object[]{"BB", "bb@163.com", 2});        batchArgs.add(new Object[]{"CC", "cc@163.com", 3});        batchArgs.add(new Object[]{"DD", "dd@163.com", 3});        batchArgs.add(new Object[]{"EE", "ee@163.com", 2});        jdbcTemplate.batchUpdate(sql, batchArgs);    }    /**     * 执行 INSERT, UPDATE, DELETE     */    @Test    public void testUpdate(){        String sql = "UPDATE employees SET last_name = ? WHERE id = ?";        jdbcTemplate.update(sql, "Jack", 5);    }    @Test    public void testDataSource() throws SQLException {        DataSource dataSource = ctx.getBean(DataSource.class);        System.out.println(dataSource.getConnection());    }}

数据库建表

CREATE TABLE `employees` (  `id` int(8) NOT NULL AUTO_INCREMENT,  `last_name` varchar(255) DEFAULT NULL,  `email` varchar(255) DEFAULT NULL,  `dept_id` int(8) DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8;

db.properties

jdbc.user=rootjdbc.password=bai5331359jdbc.driverClass=com.mysql.jdbc.Driverjdbc.jdbcUrl=jdbc:mysql://localhost:3306/spring4?useUnicode=true&characterEncoding=utf8&characterSetResults=utf8&autoReconnect=truejdbc.initPoolSize=5jdbc.maxPoolSize=10

Bean 配置

<!-- 一注解的方式扫描指定的包 -->    <context:component-scan base-package="com.spring.example">    <!--    <context:exclude-filter type="annotation"            expression="org.springframework.stereotype.Controller" />        <context:exclude-filter type="annotation"            expression="org.springframework.web.method.ControllerAdviceBean" /> -->    </context:component-scan>     <!-- 配置属性文件 -->    <bean id="propertyConfigurer"        class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">        <property name="locations">            <list>                <value>classpath:db.properties</value>                <!-- <value>/WEB-INF/classes/redis.properties</value> -->            </list>        </property>    </bean>    <!-- 配置 C3P0 数据源 -->    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">        <property name="user" value="${jdbc.user}"></property>        <property name="password" value="${jdbc.password}"></property>        <property name="jdbcUrl" value="${jdbc.jdbcUrl}"></property>        <property name="driverClass" value="${jdbc.driverClass}"></property>        <property name="initialPoolSize" value="${jdbc.initPoolSize}"></property>        <property name="maxPoolSize" value="${jdbc.maxPoolSize}"></property>    </bean>    <!-- 配置 Spirng 的 JdbcTemplate -->    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">        <property name="dataSource" ref="dataSource"></property>    </bean><!-- 配置 NamedParameterJdbcTemplate, 该对象可以使用具名参数, 其没有无参数的构造器, 所以必须为其构造器指定参数 -->    <bean id="namedParameterJdbcTemplate"        class="org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate">        <constructor-arg ref="dataSource"></constructor-arg>        </bean>

小结

Spring 自生提供了 JDBC 的底层API，同时也支持其他持久层的整合比如 Hibernate、Mybatis等。只不过不同的持久层使用了不同的 “JdbcTemplate”。实现高度热拔插式的封装，这是Spring 受欢迎的一大因素。
由于Spring 自生提供的JDBC API 在实际的项目中很少用到在这里我们简单了解一下，后续将会详细介绍Spring 整个主流的持久层框架比如 Mybatis 和 Hibernate等。

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