怎么看一个网站是否是外包做的,新开传奇网站发布网站,软件网站关键词优化,山东做网站找哪家好一 关系
1 应用 数据是存在关系的#xff0c;将有关系的数据通过 MyBatis 持久化到数据库#xff0c;且存储的数据也能表示出来这种关系#xff0c;再由数据库中把有关系的数据查询出来在页面展示。 保存#xff1a;页面数据 — Java 对象封装 — MyBatis — …一 关系
1 应用 数据是存在关系的将有关系的数据通过 MyBatis 持久化到数据库且存储的数据也能表示出来这种关系再由数据库中把有关系的数据查询出来在页面展示。 保存页面数据 — Java 对象封装 — MyBatis — 数据库表数据 查询数据库表数据 — MyBatis — 封装成 Java 对象 — 页面展示数据 使用数据库表设计来表示数据之间关系使用 Java 类设计来表示对象之间关系通过 MyBatis 配置来映射上面两者。
2 对象关系分类
关联关系 聚合关系 组合关系
泛化关系 实现关系 依赖关系3 关联关系分类 A 对象依赖 B 对象并把 B 作为 A 的一个成员变量则 A 和 B 存在关联关系。在 UML 中依赖通常使用实线箭头表示。
① 按导航分 若通过 A 对象中的某一个属性可以访问到 B 对象则说 A 可以导航到 B。 单向只能从 A 通过属性导航到 BB 不能导航到 A。 双向A 可以通过属性导航到 BB 也可以通过属性导航到 A。 ② 按多重性分 一对一一个人对一个身份证号 一对多一个部门对多个员工 多对一多个员工对一个部门 多对多多个班级对多个老师
4 判断对象关系 判断关系必须确定具体需求根据对象的属性从对象的实例上进行判断
5 注释
① useGeneratedKeys useGeneratedKeys“true” 和 keyProperty“id” 是 MyBatis 的映射文件中用于处理自动插入 ID 的配置选项。 useGeneratedKeys“true”默认为false: 让MyBatis 启用 JDBC 的 getGeneratedKeys 方法获取数据库自动生成的键值。通常这个键值是主键例如 MySQL 的 AUTO_INCREMENT 字段。 keyProperty“id”: 这个设置指定了将自动生成的键值设置到哪个 Java 对象的属性中。在这它是 id所以 MyBatis 会将自动生成的键值设置到 Java 对象的 id 属性中。 这两个设置通常一起使用以便在插入新记录后自动填充 Java 对象的 ID 属性。调用这个插入方法并传入一个对象时MyBatis 会将这个对象插入到数据库中然后获取自动生成的 ID 值并将其设置到这个对象的 id 属性中。
6 项目准备
pom
?xml version1.0 encodingUTF-8?
project xmlnshttp://maven.apache.org/POM/4.0.0 xmlns:xsihttp://www.w3.org/2001/XMLSchema-instancexsi:schemaLocationhttp://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsdmodelVersion4.0.0/modelVersiongroupIdcn.tj/groupIdartifactIdplay/artifactIdversion1.0-SNAPSHOT/versionpropertiesproject.build.sourceEncodingUTF-8/project.build.sourceEncodingmaven.compiler.source1.7/maven.compiler.sourcemaven.compiler.target1.7/maven.compiler.target/propertiesdependenciesdependencygroupIdorg.mybatis/groupIdartifactIdmybatis/artifactIdversion3.4.5/version/dependencydependencygroupIdmysql/groupIdartifactIdmysql-connector-java/artifactIdversion5.1.45/versionscoperuntime/scope/dependencydependencygroupIdlog4j/groupIdartifactIdlog4j/artifactIdversion1.2.17/version/dependencydependencygroupIdjunit/groupIdartifactIdjunit/artifactIdversion4.12/versionscopetest/scope!-- 测试阶段才用 --/dependencydependencygroupIdorg.projectlombok/groupIdartifactIdlombok/artifactIdversion1.18.22/versionscopeprovided/scope!-- 编译阶段和测试阶段才使用 --/dependency/dependencies
/projectdb.properties
jdbc.drivercom.mysql.jdbc.Driver
jdbc.urljdbc:mysql:///play_web
jdbc.usernameroot
jdbc.passwordrootlog4j.properties
log4j.rootLoggererror, stdout
log4j.logger.cn.tjTRACE
log4j.appender.stdoutorg.apache.log4j.ConsoleAppender
log4j.appender.stdout.layoutorg.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern%5p [%t] - %m%nmybatis-config.xml
?xml version1.0 encodingUTF-8 ?
!DOCTYPE configurationPUBLIC -//mybatis.org//DTD Config 3.0//ENhttp://mybatis.org/dtd/mybatis-3-config.dtd
configurationproperties resourcedb.properties/propertiestypeAliasespackage namecn.tj.domain//typeAliasesenvironments defaultdevenvironment iddevtransactionManager typeJDBC/transactionManagerdataSource typePOOLEDproperty namedriver value${jdbc.driver}/property nameurl value${jdbc.url}/property nameusername value${jdbc.username}/property namepassword value${jdbc.password}//dataSource/environment/environmentsmappers!--开启mapper目录扫描mapper接口和xml文件必须目录结构一致--package namecn.tj.mapper//mappers
/configuration二 单向多对一保存
1 数据库表
建立一个部门和两个员工这两个员工属于这个部门
// 部门表
CREATE TABLE department (id bigint(11) NOT NULL AUTO_INCREMENT,name varchar(50) DEFAULT NULL,PRIMARY KEY (id)
) ENGINEInnoDB AUTO_INCREMENT13 DEFAULT CHARSETutf8;// 员工表
CREATE TABLE employee (id bigint(11) NOT NULL AUTO_INCREMENT,name varchar(50) DEFAULT NULL,salary double(10,2) DEFAULT NULL,dept_id bigint(11) DEFAULT NULL,PRIMARY KEY (id)
) ENGINEInnoDB AUTO_INCREMENT13 DEFAULT CHARSETutf8;2 实体类
部门实体类
Data
NoArgsConstructor
AllArgsConstructor
public class Department {private Long id;private String name;
}员工实体类
Data
NoArgsConstructor
AllArgsConstructor
public class Employee {private Long id;private String name;private Double salary;//设置部门属性private Department department;
}3 Mapper 接口
部门接口
public interface DepartmentMapper {/*增加部门*/public int insertDept(Department department);/*根据id查询*/public Department queryById(Long id);
}员工接口
public interface EmployeeMapper {/*增加员工*/int insertEmp(Employee employee);/*根据id查询*/Employee queryById(Long id);/*根据员工id关联查询*/Employee selectById(Long id);
}4 Mapper XML
部门xml
?xml version1.0 encodingUTF-8?
!DOCTYPE mapper PUBLIC -//mybatis.org//DTD Mapper 3.0//EN http://mybatis.org/dtd/mybatis-3-mapper.dtd
mapper namespacecn.tj.mapper.DepartmentMapper!--增加部门useGeneratedKeystrue keyPropertyid 获取增加数据的自增主键值--insert idinsertDept useGeneratedKeystrue keyPropertyidinsert into department (name)values(#{name})/insertselect idqueryById resultTypedepartmentSELECT * from department WHERE id#{id}/select
/mapper员工xml
?xml version1.0 encodingUTF-8?
!DOCTYPE mapper PUBLIC -//mybatis.org//DTD Mapper 3.0//EN http://mybatis.org/dtd/mybatis-3-mapper.dtd
mapper namespacecn.tj.mapper.EmployeeMapper
!--增加员工--insert idinsertEmpinsert into employee (name,salary,dept_id)values(#{name},#{salary},#{department.id})/insert!--自定义返回结果常用在多表关联查询返回结果集--!--resultMap标签可封装自定义的结果集给多个查询语句使用type查询的返回结果对应的javaBean的全类名获别名--resultMap idempMap typeemployee!--配置javaBean属性和数据库表字段的映射关系:column是数据库字段property是实体类属性id配置主键字段关联关系 result配置非主键关联--id columnid propertyid/idresult columnname propertyname/resultresult columnsalary propertysalary/resultresult columndept_id propertydepartment.id/result/resultMap!--根据员工id查询--select idqueryById resultMapresMapSELECT * from employee WHERE id#{id}/select!--通过框架参数来设置发送sql--resultMap idresMap typeemployee!--配置javaBean属性和数据库表字段的映射关系:id配置主键字段关联关系 result配置非主键关联--id columnid propertyid/idresult columnname propertyname/result!--配置多对一关系中的一的一方:property多方实体类中设置的一方的属性名称column执行多方sql需要传递给下一条sql的字段名(id)select需要调用的一方的sql执行的方法(namespaceid)javaType一方实体类全类名或别名--association propertydepartment columndept_idselectcn.tj.mapper.DepartmentMapper.queryByIdjavaTypedepartment /association/resultMapresultMap idbaseMap typeemployee!--配置多方实体类属性参数--id columnid propertyid/idresult columnname propertyname/resultresult columnsalary propertysalary/result!--配置一方的实体类属性参数--association propertydepartment javaTypedepartmentid columndid propertyid/idresult propertyname columndname/result/association/resultMap!--多表关联查询员工部门信息--select idselectById resultMapbaseMapSELECT e.id,e.name,e.salary salary,d.id did,d.name dnamefrom employee e,department dWHERE e.dept_idd.id and e.id#{id};/select
/mapper5 测试类
public class EmployeeMapperTest {// 保存两个同部门下的员工Testpublic void emp_save(){//1.创建sqlsessionSqlSession sqlSession MybatisUtil.getSqlSession();//2.创建mapper对象EmployeeMapper employeeMapper sqlSession.getMapper(EmployeeMapper.class);DepartmentMapper departmentMapper sqlSession.getMapper(DepartmentMapper.class);//3.增加一个部门Department deptnew Department();dept.setName(安保部);departmentMapper.insertDept(dept);//4.新增的部门下面增加两个员工Employee emp1 new Employee();emp1.setName(石昊);emp1.setSalary(new Double(8848));emp1.setDepartment(dept);//建立员工和部门的关系Employee emp2 new Employee();emp2.setName(叶凡);emp2.setSalary(new Double(8848));emp2.setDepartment(dept);employeeMapper.insertEmp(emp1);employeeMapper.insertEmp(emp2);}
}三 单向多对一的额外 SQL 查询
1 介绍 额外sql的本质就是分步sql通过前一个的结果集进行下一条语句的查询
2 Mapper 接口
员工
Employee queryById(Long id);部门
Department queryById(Long id);3 Mapper XML
员工
!--自定义返回结果常用在多表关联查询返回结果集--
!--resultMap标签可封装自定义的结果集给多个查询语句使用type查询的返回结果对应的javaBean的全类名获别名
--
resultMap idempMap typeemployee!--配置javaBean属性和数据库表字段的映射关系:column是数据库字段property是实体类属性id配置主键字段关联关系 result配置非主键关联--id columnid propertyid/idresult columnname propertyname/resultresult columnsalary propertysalary/resultresult columndept_id propertydepartment.id/result
/resultMap
!--根据员工id查询--
select idqueryById resultMapempMapSELECT * from employee WHERE id#{id}
/select部门
select idqueryById resultTypedepartmentSELECT * from department WHERE id#{id}
/select4 测试类 // 额外sql之手动发送sql:查询15号员工所在部门Testpublic void emp_queryById() {SqlSession sqlSessionMybatisUtil.getSqlSession();EmployeeMapper employeeMapper sqlSession.getMapper(EmployeeMapper.class);DepartmentMapper departmentMapper sqlSession.getMapper(DepartmentMapper.class);//根据员工id查询Employee employee employeeMapper.queryById(15l);//根据员工所在 的部门id查部门Department department departmentMapper.queryById(employee.getDepartment().getId());System.out.println(employeedepartment.getName());}5 association 发送额外 SQL
① 员工 Mapper XML
select idqueryById resultMapresMapSELECT * from employee WHERE id#{id}/select!--通过框架参数来设置发送sql--resultMap idresMap typeemployee!--配置javaBean属性和数据库表字段的映射关系:id配置主键字段关联关系 result配置非主键关联--id columnid propertyid/idresult columnname propertyname/result!--配置多对一关系中的一的一方:property多方实体类中设置的一方的属性名称column执行多方sql需要传递给下一条sql的字段名(id)select需要调用的一方的sql执行的方法(namespaceid)javaType一方实体类全类名或别名--association propertydepartment columndept_idselectcn.tj.mapper.DepartmentMapper.queryByIdjavaTypedepartment /association/resultMap② 员工 Mapper 接口
Employee queryById(Long id);③ 测试类 Testpublic void emp_queryByEmpId() {SqlSession sqlSessionMybatisUtil.getSqlSession();EmployeeMapper employeeMapper sqlSession.getMapper(EmployeeMapper.class);//根据员工id查询Employee employee employeeMapper.queryById(15l);System.out.println(employee);}四 单向多对一的关联查询
1 员工 mapper 接口
Employee selectById(Long id);2 员工 mapper xml resultMap idbaseMap typeemployee!--配置多方实体类属性参数--id columnid propertyid/idresult columnname propertyname/resultresult columnsalary propertysalary/result!--配置一方的实体类属性参数column可用别名--association propertydepartment javaTypedepartmentid columndid propertyid/idresult propertyname columndname/result/association/resultMap!--多表关联查询员工部门信息--select idselectById resultMapbaseMapSELECT e.id,e.name,e.salary salary,d.id did,d.name dnamefrom employee e,department dWHERE e.dept_idd.id and e.id#{id};/select3 测试类 Testpublic void emp_selectByEmpId() {SqlSession sqlSessionMybatisUtil.getSqlSession();EmployeeMapper employeeMapper sqlSession.getMapper(EmployeeMapper.class);//根据员工id查询Employee employee employeeMapper.selectById(15l);System.out.println(employee);}五 单向一对多的保存与查询
1 数据库表 无变化
2 实体类
员工
Data
NoArgsConstructor
AllArgsConstructor
public class Employee {private Long id;private String name;private Double salary;// 封装员工的部门id 非关联属性private Long dept_id;
}部门 – 一对多时在一方设置多方属性
Data
NoArgsConstructor
AllArgsConstructor
public class Department {private Long id;private String name;/*设置多方的属性*/private ListEmployee employeeListnew ArrayList();
}3 Mapper 接口
员工
public interface EmployeeMapper {/*增加员工*/int insertEmp(Employee employee);/*根据部门id查询员工*/ListEmployee queryById(Long id);
}部门
public interface DepartmentMapper {/*增加部门*/public int insertDept(Department department);/*根据id查询*/public Department queryById(Long id);
}4 Mapper XML
员工
?xml version1.0 encodingUTF-8?
!DOCTYPE mapper PUBLIC -//mybatis.org//DTD Mapper 3.0//EN http://mybatis.org/dtd/mybatis-3-mapper.dtd
mapper namespacecn.tj.mapper.EmployeeMapper!--增加员工--insert idinsertEmpinsert into employee (name,salary,dept_id)values(#{name},#{salary},#{dept_id})/insert!--根据部门id查询员工--select idqueryById resultTypeemployeeSELECT * from employee WHERE dept_id#{id}/select
/mapper部门
?xml version1.0 encodingUTF-8?
!DOCTYPE mapper PUBLIC -//mybatis.org//DTD Mapper 3.0//EN http://mybatis.org/dtd/mybatis-3-mapper.dtd
mapper namespacecn.tj.mapper.DepartmentMapper!--增加部门useGeneratedKeystrue keyPropertyid 获取增加数据的自增主键值--insert idinsertDept useGeneratedKeystrue keyPropertyidinsert into department (name)values(#{name})/insert!--部门查询的自定义结果集对象--resultMap iddeptMap typedepartment!--一方实体类参数配置 ofType多方属性对应的实体类全类名或别名--id columnid propertyid/idresult columnname propertyname/resultcollection propertyemployeeList selectcn.tj.mapper.EmployeeMapper.queryByIdcolumnid ofTypeemployee/collection/resultMap!--根据id查询--select idqueryById resultMapdeptMapSELECT * from department WHERE id#{id}/select
/mapper5 测试类
员工
public class EmployeeMapperTest {// 保存一个部门和两个员工且这两个员工都是这个部门的Testpublic void emp_save(){//1.创建sqlsessionSqlSession sqlSession MybatisUtil.getSqlSession();//2.创建mapper对象EmployeeMapper employeeMapper sqlSession.getMapper(EmployeeMapper.class);DepartmentMapper departmentMapper sqlSession.getMapper(DepartmentMapper.class);//3.增加一个部门Department departmentnew Department();department.setName(实施部);departmentMapper.insertDept(department);//4.新增的部门下面增加两个员工Employee emp1new Employee();emp1.setName(利威尔);emp1.setSalary(new Double(8848));//设置部门关联idemp1.setDept_id(department.getId());employeeMapper.insertEmp(emp1);Employee emp2new Employee();emp2.setName(艾伦);emp2.setSalary(new Double(8848));//设置部门关联idemp2.setDept_id(department.getId());employeeMapper.insertEmp(emp2);}
}部门
public class DepartmentMapperTest {// 根据 id 查询部门并把其部门的员工信息也查询出来。Testpublic void dept_list() {SqlSession sqlSession MybatisUtil.getSqlSession();DepartmentMapper mapper sqlSession.getMapper(DepartmentMapper.class);Department department mapper.queryById(805l);System.out.println(department);}
}六 单向多对多的保存
1 数据库表
//学生表
CREATE TABLE student (id bigint(11) NOT NULL AUTO_INCREMENT,name varchar(50) DEFAULT NULL,PRIMARY KEY (id)
) ENGINEInnoDB AUTO_INCREMENT21 DEFAULT CHARSETutf8;
//老师表
CREATE TABLE teacher (id bigint(11) NOT NULL AUTO_INCREMENT,name varchar(50) DEFAULT NULL,PRIMARY KEY (id)
) ENGINEInnoDB AUTO_INCREMENT21 DEFAULT CHARSETutf8;
//中间表
CREATE TABLE student_teacher (student_id bigint(20) DEFAULT NULL,teacher_id bigint(20) DEFAULT NULL
) ENGINEInnoDB DEFAULT CHARSETutf8;2 实体类
// 学生
Data
public class Student {private Long id;private String name;/*设置老师属性*/private ListTeacher teacherListnew ArrayList();
}
// 老师
Data
public class Teacher {private Long id;private String name;
}3 Mapper 接口
// 学生
public interface StudentMapper {/*增加学生*/public int insertStudent(Student student);/*增加中间表数据*/public int insertRelation(Param(sid)Long sid,Param(tid)Long tid);
}// 老师
public interface TeacherMapper {/*增加老师*/int insertTeacher(Teacher teacher);
}4 Mapper XML
// 学生
?xml version1.0 encodingUTF-8?
!DOCTYPE mapper PUBLIC -//mybatis.org//DTD Mapper 3.0//EN http://mybatis.org/dtd/mybatis-3-mapper.dtd
mapper namespacecn.tj.mapper.StudentMapper!--增加学生--insert idinsertStudent useGeneratedKeystrue keyPropertyidinsert into student(name) values(#{name})/insert!--增加中间表数据--insert idinsertRelationinsert into student_teacher (student_id,teacher_id)values(#{sid},#{tid})/insert
/mapper
// 老师
?xml version1.0 encodingUTF-8?
!DOCTYPE mapper PUBLIC -//mybatis.org//DTD Mapper 3.0//EN http://mybatis.org/dtd/mybatis-3-mapper.dtd
mapper namespacecn.tj.mapper.TeacherMapper!--增加老师--insert idinsertTeacher useGeneratedKeystrue keyPropertyidinsert into teacher(name) VALUES(#{name})/insert
/mapper5 测试类
public class StudentMapperTest {//保存两个学生和两个老师且这两个老师都教了这个两个学生Testpublic void student_save() {SqlSession sqlSession MybatisUtil.getSqlSession();StudentMapper studentMapper sqlSession.getMapper(StudentMapper.class);TeacherMapper teacherMapper sqlSession.getMapper(TeacherMapper.class);//1.保存学生Student student1new Student();student1.setName(陈汉生);studentMapper.insertStudent(student1);Student student2new Student();student2.setName(穿山甲);studentMapper.insertStudent(student2);//2.保存老师Teacher teacher1new Teacher();teacher1.setName(沈幼楚);teacherMapper.insertTeacher(teacher1);Teacher teacher2new Teacher();teacher2.setName(慕容鱼);teacherMapper.insertTeacher(teacher2);//3.保存中间表数据studentMapper.insertRelation(student1.getId(),teacher1.getId());studentMapper.insertRelation(student1.getId(),teacher2.getId());studentMapper.insertRelation(student2.getId(),teacher1.getId());studentMapper.insertRelation(student2.getId(),teacher2.getId());}
}七 单向多对多的额外 SQL 查询
1 mapper 接口
// 学生
/*根据id查询学生*/
public Student queryById(Long id);// 老师
/*根据学生id查询老师信息*/
ListTeacher queryBySid(Long sid);2 mapper xml !--学生--resultMap idstudentMap typestudentid columnid propertyid/idresult columnname propertyname/resultcollection propertyteacherList columnidselectcn.tj.mapper.TeacherMapper.queryBySidofTypeteacher/collection/resultMap!--根据id查询--select idqueryById resultMapstudentMapSELECT * from student WHERE id #{id}/select!--老师--!--查询学生关联的老师--select idqueryBySid resultTypeTeacherSELECT * from teacher t,student_teacher stWHERE t.idst.teacher_id and st.student_id#{sid}/select3 测试类 // 根据 id 查询学生并查询教过他的老师Testpublic void student_query() {SqlSession sqlSession MybatisUtil.getSqlSession();StudentMapper mapper sqlSession.getMapper(StudentMapper.class);Student student mapper.queryById(2l);System.out.println(student);}八 单向多对多的删除 先删中间表(删除学生)
1 mapper 接口 /*根据id删除*/public int deleteById(Long id);/*根据学生id删除中间表数据*/public int deleteBySid(Long sid);2 mapper xml !--根据id删除--delete iddeleteByIdDELETE from student WHERE id#{id}/delete!--根据学生id删除中间表数据--delete iddeleteBySidDELETE from student_teacher WHERE student_id#{sid}/delete3 测试类 /*根据id删除学生*/Testpublic void student_delete() {SqlSession sqlSession MybatisUtil.getSqlSession();StudentMapper mapper sqlSession.getMapper(StudentMapper.class);mapper.deleteBySid(2l);//需要先删除中间表数据mapper.deleteById(2l);//再删除学生表数据}
