Mybatis中的动态SQL-where，trim标签
目录
1.where标签（它可以去掉开头的and，但不能去掉结尾的and）-实现多条件查询例子
2.Trim标签（prefixOverrides可以去掉开头的and。suffixOverrides标签可以去掉结尾的and）
3.set标签（可以解决更新数据表时字符串拼接“，”问题）
4.foreach标签遍历数组和，集合和包装类
4.1遍历数组
4.2遍历集合
4.3遍历包装类
5.sql标签（他可以将重复的SQL代码提取出来）
1.where标签（它可以去掉开头的and，但不能去掉结尾的and）-实现多条件查询例子
User.java:
package com.sikiedu.bean;
public class User {
private Integer id;
private String username;
private String password;
private String sex;
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 getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", password=" + password + ", sex=" + sex + "]";
}
}
UserMapper.java:
package com.sikiedu.mapper;
import java.util.List;
import com.sikiedu.bean.User;
public interface UserMapper {
public User selectUserById(Integer id);
public List selectUserByName(String name);
public List selectUserListByUser(User u);
}
UserMapper.xml:
MapperTest.java:
@Test
public void Test3() throws Exception{
String resource="sqlMapConfig.xml";
InputStream in = Resources.getResourceAsStream(resource);
SqlSessionFactoryBuilder ssfb=new SqlSessionFactoryBuilder();
SqlSessionFactory ssf=ssfb.build(in);
SqlSession session = ssf.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
User u=new User();
u.setSex("男");
u.setUsername("李");
List list = mapper.selectUserListByUser(u);
for(User user:list){
System.out.println(user);
}
} 数据库：
运行结果：
2.Trim标签（prefixOverrides可以去掉开头的and。suffixOverrides标签可以去掉结尾的and）
UserMapper.java:
public List selectUserListByUserTrim(User u); UserMapper.xml:
或者：
MapperTest.java:
@Test
public void Test4() throws Exception{
String resource="sqlMapConfig.xml";
InputStream in = Resources.getResourceAsStream(resource);
SqlSessionFactoryBuilder ssfb=new SqlSessionFactoryBuilder();
SqlSessionFactory ssf=ssfb.build(in);
SqlSession session = ssf.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
User u=new User();
u.setSex("男");
u.setUsername("李");
List list = mapper.selectUserListByUserTrim(u);
for(User user:list){
System.out.println(user);
}
} 运行结果：
3.set标签（可以解决更新数据表时字符串拼接“，”问题）
UserMapper.java:
public void updateSetUser(User u);UserMapper.xml:
update user3
username=#{username},
password=#{password},
sex=#{sex}
where id=#{id}
MapperTest.java:
@Test
public void Test5() throws Exception{
String resource="sqlMapConfig.xml";
InputStream in = Resources.getResourceAsStream(resource);
SqlSessionFactoryBuilder ssfb=new SqlSessionFactoryBuilder();
SqlSessionFactory ssf=ssfb.build(in);
SqlSession session = ssf.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
User u=new User();
u.setId(3);
u.setUsername("张三三");
u.setPassword("3333");
u.setSex("女");
mapper.updateSetUser(u);
session.commit();
}运行结果:
4.foreach标签遍历数组和，集合和包装类
4.1遍历数组
UserMapper.java:
public List selectUserListByIds(Integer[] ids); UserMapper.xml:
MapperTest.java:
@Test
public void Test6() throws Exception{
String resource="sqlMapConfig.xml";
InputStream in = Resources.getResourceAsStream(resource);
SqlSessionFactoryBuilder ssfb=new SqlSessionFactoryBuilder();
SqlSessionFactory ssf=ssfb.build(in);
SqlSession session = ssf.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
Integer[] ids={1,3,4};
List list = mapper.selectUserListByIds(ids);
for (User user : list) {
System.out.println(user);
}
} 运行结果：
4.2遍历集合
UserMapper.java:
public List selectUserListByList(List idList); UserMapper.xml:
MapperTest.java:
@Test
public void Test7() throws Exception{
String resource="sqlMapConfig.xml";
InputStream in = Resources.getResourceAsStream(resource);
SqlSessionFactoryBuilder ssfb=new SqlSessionFactoryBuilder();
SqlSessionFactory ssf=ssfb.build(in);
SqlSession session = ssf.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
List idList=new ArrayList();
idList.add(1);
idList.add(3);
idList.add(4);
List list = mapper.selectUserListByList(idList);
for (User user : list) {
System.out.println(user);
}
} 运行结果：
4.3遍历包装类
UserVo.java:
package com.sikiedu.bean;
import java.util.List;
public class UserVo extends User {
private List idList;
public List getIdList() {
return idList;
}
public void setIdList(List idList) {
this.idList = idList;
}
} UserMapper.java:
public List selectUserListByUserVo(UserVo vo); UserMapper.xml:
MapperTest.java:
@Test
public void Test8() throws Exception{
String resource="sqlMapConfig.xml";
InputStream in = Resources.getResourceAsStream(resource);
SqlSessionFactoryBuilder ssfb=new SqlSessionFactoryBuilder();
SqlSessionFactory ssf=ssfb.build(in);
SqlSession session = ssf.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
List idList=new ArrayList();
idList.add(1);
idList.add(3);
idList.add(4);
UserVo vo=new UserVo();
vo.setIdList(idList);
List list = mapper.selectUserListByUserVo(vo);
for (User user : list) {
System.out.println(user);
}
} 运行结果：
5.sql标签（他可以将重复的SQL代码提取出来）
select *
from user3
使用时，只需要将select * from user3替换成