Java——JDBC Template

Posted 2021-03-04 明王不动心

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1.JDBC Template概念

为了简化持久化操作，Spring在JDBC API之上提供了JDBC Template组件。
传统操作方式：

使用JDBC Template操作方式：

JDBC Template提供统一的模板方法，在保留代码灵活性的基础上，尽量减少持久化代码。

基于JDBC的API的开发案例：

String sql = "select * from user";
Statement stmt = conn.createStatement();
ResultSet resultSet = stmt.executeQuery(sql);
while (resultSet.next()){
    int uid = resultSet.getInt("uid");
    String name = resultSet.getString("name");
    String mobile = resultSet.getString("mobile");
    String addr = resultSet.getString("addr");
    System.out.println(uid+"  "+name+"  "+mobile+"  "+addr);
}

基于JDBC Template的开发案例：
Integer count = jt.queryForObject("select * from user",Integer.class);

2.环境依赖

（1）依赖导入

<properties>
    <spring.version>4.2.4.RELEASE</spring.version>
</properties>
<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>compile</scope>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.44</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-beans</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-aop</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-tx</artifactId>
        <version>${spring.version}</version>
    </dependency>
</dependencies>

（2）bean配置

<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop.xsd
    http://www.springframework.org/schema/tx
    http://www.springframework.org/schema/tx/spring-tx.xsd">
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://148.70.251.10:3306/selection_course?useUnicode=yes&amp;characterEncoding=utf8"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
    </bean>

    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="dataSource"/>
    </bean>
</beans>

3.简单使用

1）execute方法——一般用来执行DDL语句，与表操作相关

@org.junit.Test
public void testExecute(){
    ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
    JdbcTemplate jdbcTemplate = (JdbcTemplate) context.getBean("jdbcTemplate");
    jdbcTemplate.execute("create table test(id int,name varchar(32))");
}

2）update与batchUpdate方法——对数据进行增删改

将jdbcTemplate提取出来，方便后面多次利用。

private JdbcTemplate jdbcTemplate;
{
    ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
    jdbcTemplate = (JdbcTemplate) context.getBean("jdbcTemplate");
}

（1）update：对数据进行增删改操作

　　int update(String sql, Object[] args)
　　int update(String sql, Object... args)

@org.junit.Test
public void testExecute(){
    jdbcTemplate.execute("create table test(id int,name varchar(32))");
}

@org.junit.Test
public void testUpdate(){
    String sql = "insert into student(name,sex) values(?,?)";
    jdbcTemplate.update(sql,new Object[]{"ming","boy"});
}

（2）batchUpdate方法：批量增删改操作

　　int[] batchUpdate(String[] sql)
　　int[] batchUpdate(String sql, List<Object[]>)

@org.junit.Test
public void testBatchUpdate(){
    String[] sqls = {
            "insert into student(name,sex) values(\'kebi\',\'boy\')",
            "insert into student(name,sex) values(\'maoxian\',\'boy\')",
            "insert into student(name,sex) values(\'jiaqi\',\'girl\')",
            "insert into student(name,sex) values(\'xue\',\'girl\')",
            "update student set name=\'xuejiaqi\' where name=\'xue\'"
    };
    int[] ret = jdbcTemplate.batchUpdate(sqls);
    System.out.println(ret);
}

@org.junit.Test
public void testBatchUpdate2(){
    String sql = "insert into selection(student,course) values(?,?)";
    List<Object[]> list =  new ArrayList<Object[]>();
    list.add(new Object[]{2001,1001});
    list.add(new Object[]{2002,1003});
    int[] ret = jdbcTemplate.batchUpdate(sql, list);
    for (int r: ret){
        System.out.println(r);  //返回值1表示成功
    }
}

3）query与queryXXX方法——对数据进行查询操作

查询简单数据项
（1）获取一个
　　T queryForObject(String sql, Class<T> type)
　　T queryForObject(String sql, Class[] args, Class<T> type)
　　T queryForObject(String sql, Class<T> type, Object... args)

（2）获取多个
　　List<T> queryForList(String sql, Class<T> type)
　　List<T> queryForList(String sql, Object[] args, Class<T> type)
　　LIst<T> queryForList(String sql, Class<T> type, Object... args)

简单示例：

    //查询单个数据
    @org.junit.Test
    public void testQuerySimple(){
        String sql = "select count(*) from student";
        int count = jdbcTemplate.queryForObject(sql, Integer.class);
        System.out.println(count);  //4
    }

    //查询多个数据
    @org.junit.Test
    public void testQuerySimple2(){
        String sql = "select NAME from student";
        List<String> names = jdbcTemplate.queryForList(sql,String.class);
        System.out.println(names);
    }

    //查询一个对象
    @org.junit.Test
    public void testQueryMap(){
        String sql = "select * from student where id = ?";
        Map<String,Object> s =jdbcTemplate.queryForMap(sql,2001);
        System.out.println(s);  //{id=2001, name=ming_test, sex=boy, born=null}
    }

    //查询多个对象
    @org.junit.Test
    public void testQueryMap2(){
        String sql = "select * from student";
        List<Map<String,Object>> s =jdbcTemplate.queryForList(sql);
        System.out.println(s);
//        [{id=2001, name=ming_test, sex=boy, born=null},
//        {id=2002, name=kebi, sex=boy, born=null},
//        {id=2003, name=maoxian, sex=boy, born=null},
//        {id=2005, name=xuejiaqi, sex=girl, born=null}]

    }

如果将查询结果进行映射了？这样方面后期的数据处理。
封装一条数据：

public void testQueryEntity(){
    String sql = "select * from student where id = ?";
    Student stu = jdbcTemplate.queryForObject(sql, new RowMapper<Student>() {
        public Student mapRow(ResultSet resultSet, int i) throws SQLException {
            Student stu = new Student();
            stu.setId(resultSet.getInt("id"));
            stu.setName(resultSet.getString("name"));
            stu.setSex(resultSet.getString("sex"));
            stu.setBorn(resultSet.getDate("born"));
            return stu;
        }
    }, 2001);
    System.out.println(stu);  //Student{2001,ming_test,boy,null}
}

封装多条数据：

@org.junit.Test
public void testQueryEntity2(){
    String sql = "select * from student";
    List<Student> list = jdbcTemplate.query(sql, new RowMapper<Student>() {
        public Student mapRow(ResultSet resultSet, int i) throws SQLException {
            Student stu = new Student();
            stu.setId(resultSet.getInt("id"));
            stu.setName(resultSet.getString("name"));
            stu.setSex(resultSet.getString("sex"));
            stu.setBorn(resultSet.getDate("born"));
            return stu;
        }
    });
    System.out.println(list);
}

可以将rowmapper封装成一个对象：

@org.junit.Test
public void testQueryEntity(){
    String sql = "select * from student where id = ?";
    Student stu = jdbcTemplate.queryForObject(sql, new StudentRowMapper(), 2001);
    System.out.println(stu);  //Student{2001,ming_test,boy,null}
}

@org.junit.Test
public void testQueryEntity2(){
    String sql = "select * from student";
    List<Student> list = jdbcTemplate.query(sql, new StudentRowMapper());
    System.out.println(list);
}
private class StudentRowMapper implements RowMapper<Student>{
    public Student mapRow(ResultSet resultSet, int i) throws SQLException {
        Student stu = new Student();
        stu.setId(resultSet.getInt("id"));
        stu.setName(resultSet.getString("name"));
        stu.setSex(resultSet.getString("sex"));
        stu.setBorn(resultSet.getDate("born"));
        return stu;
    }
}

4.JDBC Template持久层示例

（1）接口类

//定义student查询接口
public interface StudentDao {
    void insert(Student stu);
    void update(Student stu);
    void delete(int id);
    Student select(int id);
    List<Student> selectAll();
}


public class Student {
    private int id;
    private String name;
    private String sex;
    private Date born;

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Date getBorn() {
        return born;
    }

    public void setBorn(Date born) {
        this.born = born;
    }

    @Override
    public String toString() {
        return "Student{" +id+","+name+","+sex+","+born +"}";
    }
}

（2）持久层代码开发，之后都可以调用这里面的接口

@Repository  //声明持久化对象
public class StudentDaoImpl implements StudentDao {

    @Autowired  //自动注入
    private JdbcTemplate jdbcTemplate;

    public void insert(Student stu) {
        String sql = "insert into student(name,sex,born) values(?,?,?)";
        jdbcTemplate.update(sql,stu.getName(),stu.getSex(),stu.getBorn());
    }

    public void update(Student stu) {
        String sql = "update student set name=?,sex=?,born=? where id=?";
        jdbcTemplate.update(sql,stu.getName(),stu.getSex(),stu.getBorn(),stu.getId());
    }

    public void delete(int id) {
        String sql = "delete from student where id=?";
        jdbcTemplate.update(sql,id);
    }

    public Student select(int id) {
        String sql = "select * from student where id=?";
        return jdbcTemplate.queryForObject(sql,new StudentRowMapper(),id);
    }

    public List<Student> selectAll() {
        String sql = "select * from student";
        return jdbcTemplate.query(sql,new StudentRowMapper());
    }

    private class StudentRowMapper implements RowMapper<Student> {
        public Student mapRow(ResultSet resultSet, int i) throws SQLException {
            Student stu = new Student();
            stu.setId(resultSet.getInt("id"));
            stu.setName(resultSet.getString("name"));
            stu.setSex(resultSet.getString("sex"));
            stu.setBorn(resultSet.getDate("born"));
            return stu;
        }
    }
}

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