Mybatis-基础使用

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Class.forName("com.mysql.jdbc.Driver");

2. 获取数据库连接

然后需要获取数据库连接，如下所示。

// url用于标识数据库位置，即告诉Jdbc连接哪个数据库
String url = "jdbc:mysql://127.0.0.1:3306/test";
// 数据库用户名和密码
String username = "root";
String password = "root";
// Connection是数据库编程中的一个重要对象，客户端与数据库的所有交互均依赖该对象
Connection connection = DriverManager.getConnection(url, username, password);

Statement statement = connection.createStatement();

Statement statement = connection.createStatement();
String sql = "SELECT * FROM worker";
ResultSet resultSet = statement.executeQuery(sql);

由于

String sql = "SELECT * FROM worker WHERE sex = ?"
// 获取PreparedStatement对象时就需要传入SQL语句进行预编译
PreparedStatement preparedStatement = connection.prepareStatement(sql);
// 设置参数，将第一个占位符替换为"male"
preparedStatement.setString(1, "male");
// 执行查询，查询结果由ResultSet对象封装
ResultSet resultSet = preparedStatement.executeQuery();

相较于

if (resultSet != null) {
    resultSet.close();
}
if (preparedStatement != null) {
    preparedStatement.close();
}
if (connection != null) {
    connection.close();
}

二. Mybatis基础使用

1. Mybatis结构

        SELECT * FROM worker WHERE sex = #{sex}
    

原始

// 指定全局配置文件
String resource = "mybatis-config.xml";
// 读取全局配置文件
InputStream inputStream = Resources.getResourceAsStream(resource);
// 构建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 获取SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();

// 第一个参数为：（映射文件的）命名空间 + "." + （映射文件的SQL语句的）id
// 第二个参数为：需要执行的SQL语句的参数值
List workers = sqlSession.selectList("MyMapper.selectWorker", "male");

最后不要忘记关闭

if (sqlSession != null) {
    sqlSession.close();
}

3. 动态代理Mybatis使用

动态代理

        SELECT * FROM worker WHERE sex = #{sex}
    

上面的映射文件中，

public interface WorkerMapper {

    List selectWorkerBySex(String sex);

}

动态代理

// 指定全局配置文件
String resource = "mybatis-config.xml";
// 读取全局配置文件
InputStream inputStream = Resources.getResourceAsStream(resource);
// 构建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 获取SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();

获取映射接口的实例的步骤如下所示。

WorkerMapper workerMapper = sqlSession.getMapper(WorkerMapper.class);

获取映射接口的实例后，通过调用映射接口的实例的方法来执行

List list = workerMapper.selectWorkerBySex("male");

最后关闭

if (sqlSession != null) {
    sqlSession.close();
}

三. Mybatis标签语法

本节对映射文件中的常用标签进行分析，无特殊说明时，默认

        SELECT * FROM worker WHERE age > #{age} and salary > #{salary}
    

映射接口如下所示。

public interface WorkerMapper {

    List selectAgeSalaryByMap(Map map);

}

测试代码如下所示（省略

......
WorkerMapper workerMapper = sqlSession.getMapper(WorkerMapper.class);
Map map = new HashMap();
map.put("age", 20L);
map.put("salary", 10000L);
List workers = workerMapper.selectAgeSalaryByMap(map);
......

例子2：通过

public class SelectInfo {

    private Long age;
    private Long salary;

    public Long getAge() {
        return age;
    }

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

    public Long getSalary() {
        return salary;
    }

    public void setSalary(Long salary) {
        this.salary = salary;
    }
    
}

映射文件如下所示。

        SELECT * FROM worker WHERE age > #{age} and salary > #{salary}
    

映射接口如下所示。

public interface WorkerMapper {

    List selectAgeSalaryByBean(SelectInfo selectInfo);

}

测试代码如下所示（省略

......
WorkerMapper workerMapper = sqlSession.getMapper(WorkerMapper.class);
SelectInfo selectInfo = new SelectInfo();
selectInfo.setAge(20L);
selectInfo.setSalary(10000L);
List workers = workerMapper.selectAgeSalaryByBean(selectInfo);
......

2. 标签

        INSERT INTO
        worker (name, sex, age, salary)
        VALUES
        (#{name}, #{sex}, #{age}, #{salary})
    

映射接口如下所示。

public interface WorkerMapper {

    Integer insertWorker(Worker worker);

}

public class Worker {

    private long id;
    private String name;
    private String sex;
    private long age;
    private long salary;

    public Worker() {}

    public Worker(String name, String sex,
                  long age, long salary) {
        this.name = name;
        this.sex = sex;
        this.age = age;
        this.salary = salary;
    }

    // 省略getter和setter
    ......

}

worker表的创建语句如下。

CREATE TABLE worker(
    id INT(11) PRIMARY KEY NOT NULL AUTO_INCREMENT,
    name VARCHAR(30) NOT NULL,
    sex VARCHAR(30) NOT NULL,
    age INT(11) NOT NULL,
    salary INT(11) NOT NULL
)

测试代码如下所示（省略

...
WorkerMapper workerMapper = sqlSession.getMapper(WorkerMapper.class);
Worker worker = new Worker("Lee", "male", 20L, 10000L);
Integer result = workerMapper.insertWorker(worker);
System.out.println(result + " pieces of data were inserted.");
System.out.println("The primary key of the inserted data is " + worker.getId());
...

3. 和标签

这两个标签的属性与

CREATE TABLE book(
    id INT(11) PRIMARY KEY AUTO_INCREMENT,
    b_name VARCHAR(255) NOT NULL,
    b_price INT(11) NOT NULL
)

创建一个

public class Book {

    private long id;
    private String bookName;
    private long bookPrice;

    // 省略getter和setter
    ......

}

可以看到，

        SELECT * FROM book WHERE b_name=#{bookName}
    

public interface BookMapper {

    List selectBookByName(String bookName);

}

测试代码如下所示（省略

......
BookMapper bookMapper = sqlSession.getMapper(BookMapper.class);
List mathBooks = bookMapper.selectBookByName("Math");
......

如果

public class Book {

    private long id;
    private String bookName;
    private long bookPrice;

    private BookStore bookStore;

    // 省略getter和setter
    ......

}

public class BookStore {

    private long bsId;
    private String bsName;

    // 省略getter和setter
    ......

}

此时映射文件如下所示。

        SELECT * FROM book WHERE b_name=#{bookName}
    

关于

Mybatis

Mybatis

总结

本文对

JDBC

Mybatis

Mybatis

Mybatis

Mybatis

JDK

MappedStatement

SQL

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