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mybatis(java持久层框架)

时间：2018-10-20 10:04:03

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mybatis(java持久层框架)

mybatis java持久层框架（对JDBC进行封装,并自动完成ORM操作）

ORM框架是对象关系映射，一个对象与表中的一行数据一一对应，把对象持久化到数据库中。

我将会一步一步详细的创建一个完整的mybatis

建项目 ---- 改POM ---- 写YML(或XML) ---- 写业务

1.新建maven项目

2.在POM中添加依赖（两个）

<dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.4.6</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.47</version></dependency>

3.创建数据库

新建数据库bookshop并导入表（三个）

user表

DROP TABLE IF EXISTS `user`;CREATE TABLE `user` (`id` int(11) NOT NULL AUTO_INCREMENT,`username` varchar(20) NOT NULL,`PASSWORD` varchar(32) NOT NULL,`realname` varchar(20) DEFAULT NULL,`email` varchar(50) NOT NULL,`gender` varchar(50) NOT NULL,`flag` int(11) DEFAULT NULL,`role` int(11) DEFAULT NULL,PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;-- ------------------------------ Records of user-- ----------------------------INSERT INTO `user` VALUES ('1', 'admin', '888', '李明', 'liming@', '男', '1', '0');INSERT INTO `user` VALUES ('2', 'jiangjiang', '123456', '犟犟', 'jiangjiang@', '男', '1', '1');INSERT INTO `user` VALUES ('3', 'yitao', '123456', '艺涛', 'shuliang@', '女', '1', '1');

book表

DROP TABLE IF EXISTS `book`;CREATE TABLE `book` (`id` int(11) NOT NULL AUTO_INCREMENT,`title` varchar(50) NOT NULL,`author` varchar(20) DEFAULT NULL,`publicDate` datetime DEFAULT NULL,`publisher` varchar(50) DEFAULT NULL,`isbn` varchar(15) DEFAULT NULL,`price` decimal(8,2) DEFAULT NULL,`picture` varchar(50) DEFAULT NULL,`cid` int(11) DEFAULT NULL,PRIMARY KEY (`id`),KEY `cid` (`cid`),CONSTRAINT `book_ibfk_1` FOREIGN KEY (`cid`) REFERENCES `category` (`cid`)) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;-- ------------------------------ Records of book-- ----------------------------INSERT INTO `book` VALUES ('1', 'Java核心技术卷I 基础知识', '霍斯特曼', '-12-01 00:00:00', '机械工业出版社', '9787111636663', '102.80', null, '10');INSERT INTO `book` VALUES ('2', '高性能MySQL（第3版）', '特卡琴科', '-05-10 00:00:00', '电子工业出版社', '9787121198854', '122.90', null, '10');INSERT INTO `book` VALUES ('3', 'Java从入门到精通（第5版）', '明日科技', '-03-01 00:00:00', '清华大学出版社', '9787302517597', '61.40', null, '10');INSERT INTO `book` VALUES ('4', 'Java编程思想（第4版）', 'Bruce Eckel', '-06-01 00:00:00', '机械工业出版社', '9787111213826', '100.30', null, '10');INSERT INTO `book` VALUES ('5', '深入理解Java虚拟机', '周志明', '-06-01 00:00:00', '机械工业出版社', '9787111421900', '62.40', null, '10');INSERT INTO `book` VALUES ('6', '高等数学（第七版）（上册）', '同济大学数学系', '-07-01 00:00:00', '高等教育出版社', '9787040396638', '40.20', null, '11');INSERT INTO `book` VALUES ('7', '管理学(第13版)', '斯蒂芬·P·罗宾斯', '-01-01 00:00:00', '中国人民大学出版社', '9787300234601', '66.50', null, '14');INSERT INTO `book` VALUES ('8', '红楼梦原著版（上、下册）', '曹雪芹', '-01-01 00:00:00', '人民文学出版社', '9787020002207', '38.90', null, '12');INSERT INTO `book` VALUES ('9', '水浒传（上下册）（全两册）', '施耐庵 ,罗贯中', '-09-01 00:00:00', '人民文学出版社', '9787020008742', '32.90', null, '12');INSERT INTO `book` VALUES ('10', '西游记（共两册）', '吴承恩 ', '-05-01 00:00:00', '人民文学出版社', '978701564', '48.00', null, '12');

category表

DROP TABLE IF EXISTS `category`;CREATE TABLE `category` (`cid` int(11) NOT NULL,`cname` varchar(30) NOT NULL,PRIMARY KEY (`cid`)) ENGINE=InnoDB DEFAULT CHARSET=utf8;-- ------------------------------ Records of category-- ----------------------------INSERT INTO `category` VALUES ('10', '科技');INSERT INTO `category` VALUES ('11', '教育');INSERT INTO `category` VALUES ('12', '小说');INSERT INTO `category` VALUES ('13', '文艺');INSERT INTO `category` VALUES ('14', '经管');INSERT INTO `category` VALUES ('15', '成功');INSERT INTO `category` VALUES ('16', '生活');

4.创建mybatis配置文件（mybatis-config.xml）

xml文件内容格式

mybatis配置 JDBC环境配置mysql数据库环境配置事件管理连接池驱动urlusernamepasswordmapper注册注册mapper文件所在位置

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE configurationPUBLIC "-////DTD Config 3.0//EN""/dtd/mybatis-3-config.dtd"><configuration><environments default="MySqlDB"><environment id="MySqlDB"><transactionManager type="JDBC"></transactionManager><dataSource type="org.apache.ibatis.datasource.pooled.PooledDataSourceFactory"><property name="driver" value="com.mysql.jdbc.Driver"/><property name="url" value="jdbc:mysql://127.0.0.1:3306/bookshop?useUnicode=true&characterEncoding=UTF-8"/><property name="username" value="root"/><property name="password" value="123456"/></dataSource></environment></environments><mappers><mapper resource="*Mapper.xml"></mapper></mappers></configuration>

5.创建对应表中字段的对象

user表

public class User implements Serializable {private static final long serialVersionUID = 937774262561524430L;private Integer id;private String username;private String password;private String realname;private String email;private String gender;private Integer flag;private Integer role;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public String getRealname() {return realname;}public void setRealname(String realname) {this.realname = realname;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}public String getGender() {return gender;}public void setGender(String gender) {this.gender = gender;}public Integer getFlag() {return flag;}public void setFlag(Integer flag) {this.flag = flag;}public Integer getRole() {return role;}public void setRole(Integer role) {this.role = role;}@Overridepublic String toString() {System.out.println( "User{" +"id=" + id +", username='" + username + '\'' +", password='" + password + '\'' +", realname='" + realname + '\'' +", email='" + email + '\'' +", gender='" + gender + '\'' +", flag=" + flag +", role=" + role +'}');return null;}}

book表

/*** (Book)实体类** @author makejava* @since -07-03 11:07:37*/public class Book implements Serializable {private static final long serialVersionUID = -35101824717255137L;private Integer id;private String title;private String author;private Date publicdate;private String publisher;private String isbn;private Double price;private String picture;private Integer cid;private Category category;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getAuthor() {return author;}public void setAuthor(String author) {this.author = author;}public Date getPublicdate() {return publicdate;}public void setPublicdate(Date publicdate) {this.publicdate = publicdate;}public String getPublisher() {return publisher;}public void setPublisher(String publisher) {this.publisher = publisher;}public String getIsbn() {return isbn;}public void setIsbn(String isbn) {this.isbn = isbn;}public Double getPrice() {return price;}public void setPrice(Double price) {this.price = price;}public String getPicture() {return picture;}public void setPicture(String picture) {this.picture = picture;}public Integer getCid() {return cid;}public void setCid(Integer cid) {this.cid = cid;}public Category getCategory() {return category;}public void setCategory(Category category) {this.category = category;}@Overridepublic String toString() {return "Book{" +"id=" + id +", title='" + title + '\'' +", author='" + author + '\'' +", publicdate=" + publicdate +", publisher='" + publisher + '\'' +", isbn='" + isbn + '\'' +", price=" + price +", picture='" + picture + '\'' +", cid=" + cid +", category=" + category +'}';}}

category表

public class Category implements Serializable {private static final long serialVersionUID = -9481033681756L;private Integer cid;private String cname;public Integer getCid() {return cid;}public void setCid(Integer cid) {this.cid = cid;}public String getCname() {return cname;}public void setCname(String cname) {ame = cname;}@Overridepublic String toString() {return "Category{" +"cid=" + cid +", cname='" + cname + '\'' +'}';}}

6.定义DAO层接口

6.1新建dao层接口

public interface UserMapper {//返回数据库所有Book数据public List<User> selectAllUser();}

6.2传参

上面我们的方法是无参方法，如果我们想要传参分为两种情况，

一个参数如下

public List<User> selectAllUser(String name);

两个或两个以上的有四种方式：

6.2.1 采用Map传多参

Dao层：

方法（Map 参数）

XML ：

{key} 或 {key,dbcType=VARCHAR}

当mybatis不能自动识别传入对象类型时加入jdbcType=VARCHAR 不加也可以。

如下：

//dao层public List<User> selectAllUser(Map name);

<select id="selectIdUser" resultType="com.wjh.pojo.User">SELECT * FROM user WHERE id = #{key}</select>

6.2.2 param （param从1开始）

Dao层 :

方法（@param(“username”)String name,@param(“userpassword”)String password）

XML :

{username}或{username,dbcType=VARCHAR}

当mybatis不能自动识别传入对象类型时加入jdbcType=VARCHAR 不加也可以。

如下：

//dao层public List<User> selectAllUser(@param("username")String name,@param("userpassword")String password);

<select id="selectIdUser" resultType="com.wjh.pojo.User">SELECT * FROM user WHERE name = #{username} AND password = #{userpassword}</select>

6.2.3 args （arg从0开始）

Dao层

方法（String name，String password）

XML

{arg0} {arg1}

必须要在{}前面加上#和$ 区别为#会自动处理为字符串 $是原样放上， #会防止sql注入 $不会防止sql注入

如下：

//dao层public List<User> selectAllUser(String name，String password);

<select id="selectIdUser" resultType="com.wjh.pojo.User">SELECT * FROM user WHERE name = #{arg0} AND password = #{arg1}</select>

6.2.4 对象传参

Dao层

方法（User user）

XML

{对象函数}

如下：

//dao层public List<User> selectAllUser(User user);

<select id="selectIdUser" resultType="com.wjh.pojo.User">SELECT * FROM user WHERE name = #{name} AND password = #{password}</select>

7.写XML

新建Mapper.xml并编写Mapper.xml

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE mapperPUBLIC "-////DTD Mapper 3.0//EN""/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.wjh.dao.UserDao"><select id="selectIdUser" resultType="com.wjh.pojo.User">-- #{arg0} = 方法的第一个参数SELECT * FROM user WHERE id = #{arg0}</select></mapper>

7.测试

新建一个Test测试类

7.1首先获取mybatis配置文件的流对象

通过Resources.getResourceAsStream（“文件位置/文件名”）

7.2构建sqlsession连接工厂

SqlSessionFactoryBuilder.build(获取到mtbatis配置文档的流对象)

SqlSessionFactory是MyBatis的关键对象,它是个单个数据库映射关系经过编译后的内存镜像.SqlSessionFactory对象的实例可以通过SqlSessionFactoryBuilder对象类获得,而 SqlSessionFactoryBuilder则可以从XML配置文件或一个预先定制的Configuration的实例构建出SqlSessionFactory的实例.每一个MyBatis的应用程序都以一个SqlSessionFactory对象的实例为核心.同时SqlSessionFactory也是线程安全的,SqlSessionFactory一旦被创建,
应该在应用执行期间都存在.在应用运行期间不要重复创建多次,建议使用单例模式.SqlSessionFactory是创建SqlSession的工厂.

7.3通过工厂获取连接（SqlSession）

通过Resources.getResourceAsStream（“文件位置/文件名”）

7.4通过连接对象获取接口实现类对象

UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

7.5执行方法

public class MybatisTest {@Testpublic void test1(){try {//1.获取读取mybatis配置文件的流对象//Resources.getResourceAsStream加载资源InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");//2.构建sqlsession连接工厂 build编译 java -> classSqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);/** SqlSessionFactory是MyBatis的关键对象,它是个单个数据库映射关系经过编译后的内存镜像.SqlSessionFactory对象的实例可以通过SqlSessionFactoryBuilder对象类获得,* 而SqlSessionFactoryBuilder则可以从XML配置文件或一个预先定制的Configuration的实例构建出SqlSessionFactory的实例.* 每一个MyBatis的应用程序都以一个SqlSessionFactory对象的实例为核心.同时SqlSessionFactory也是线程安全的,SqlSessionFactory一旦被创建,* 应该在应用执行期间都存在.在应用运行期间不要重复创建多次,建议使用单例模式.SqlSessionFactory是创建SqlSession的工厂.* *///3.通过工厂获取连接SqlSession sqlSession = sqlSessionFactory.openSession();//4.通过连接对象获取接口实现类对象UserMapper userMapper = sqlSession.getMapper(UserMapper.class);User user = userMapper.selectIdUser(3,null,null,null);user.toString();// System.out.println(sqlSession.getMapper(BookMapper.class).selectAllBook().toString());//5.调用接口中的方法} catch (IOException e) {e.printStackTrace();}}}