最近需要做一个根据表名和字段更新表的功能,项目结构是springboot+jpa,记录如下:
1.经查阅资料jpa和hibernate自带对原生sql的支持都是不支持该操作的,原因是:jpa和hibernate在进行参数替换的时候是使用占位符的形式,防止了sql的注入,在解析会给参数带上单引号,但是可以通过定义原生的sql进行解决动态sql查询,但无法实现动态sql更新,如果需要更新必须获取到表对应的实体类
例子实现动态查询sql,假设目前有两张表,表ta、tb,拥有相同的字段 id 、name、desc
pom.xml
org.springframework.boot
spring-boot-starter-data-jpa
mysql
mysql-connector-java
runtime
org.springframework.boot
spring-boot-starter-web
org.springframework.boot
spring-boot-starter-test
test
org.springframework.boot
spring-boot-starter-web
ta实体类
package com.example.demo;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import java.util.Objects;
/**
* Author: hezishan
* Date: 2018/7/11.
* Description:
**/
@Entity
public class Ta {
private int id;
private String name;
private String desc;
@Id
@Column(name = "id")
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Basic
@Column(name = "name")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Basic
@Column(name = "desc")
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Ta ta = (Ta) o;
return id == ta.id &&
Objects.equals(name, ta.name) &&
Objects.equals(desc, ta.desc);
}
@Override
public int hashCode() {
return Objects.hash(id, name, desc);
}
}
动态sql类:
entityManager来定义原生sql
package com.example.demo;
import org.springframework.stereotype.Component;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import java.util.Map;
/**
* Author: hezishan
* Date: 2018/7/11.
* Description:
**/
@Component
public class UpdateResponsity {
@PersistenceContext //注入的是实体管理器,执行持久化操作
EntityManager entityManager;
public Object selectByTableNameAndAttr(String tableName,String attr,String attrVal){
String sql="select * from "+tableName + " where "+attr+" = "+attrVal;
Object object=entityManager.createNativeQuery(sql).getSingleResult();
return object;
}
}
测试类:
@RunWith(SpringRunner.class)
@SpringBootTest
public class DemoApplicationTests {
@Autowired
UpdateResponsity updateResponsity;
@Autowired
@Test
public void contextLoads() {
Object object= updateResponsity.selectByTableNameAndAttr("ta","id","1");
Object object1= updateResponsity.selectByTableNameAndAttr("tb","id","1");
System.out.println(object);
System.out.println(object1);
}
}
2.jpa和hibernate做不了,可mybatis可以实现,mybatis不同于其他持久层框架就是其能实现动态sql,mybatis提供两种方式参数的传入,分别是#、$.其区别如下:mybatis 在对 sql 语句进行预编译之前,会对 sql 进行动态解析,解析为一个 BoundSql 对象,也是在此处对动态 SQL 进行处理的。
在动态 SQL 解析阶段, #{ } 和 ${ } 会有不同的表现:#{ } 解析为一个 JDBC 预编译语句(prepared statement)的参数标记符。例如,sqlMap 中如下的 sql 语句
select * from user where name = #{name};
解析为:
select * from user where name = ?;
一个 #{ } 被解析为一个参数占位符 ? 。
而${ } 仅仅为一个纯碎的 string 替换,在动态 SQL 解析阶段将会进行变量替换
例如,sqlMap 中如下的 sql
select * from user where name = '${name}';
当我们传递的参数为 "ruhua" 时,上述 sql 的解析为:
select * from user where name = "ruhua";
预编译之前的 SQL 语句已经不包含变量 name 了。
综上所得, ${ } 的变量的替换阶段是在动态 SQL 解析阶段,而 #{ }的变量的替换是在 DBMS 中。
1.1使用注解方式:
pom.xml
dependency>
org.springframework.boot
spring-boot-starter
org.springframework.boot
spring-boot-starter-web
org.mybatis.spring.boot
mybatis-spring-boot-starter
1.3.2
mysql
mysql-connector-java
org.springframework.boot
spring-boot-starter-test
test
UpdateResposity.java:在表名和属性名的使用$作为值传入
/**
* Author: hezishan
* Date: 2018/7/11.
* Description:
**/
@Mapper
public interface UpdateResposity {
@Select("select ${id} as id,${val} as val from ${tableName} where ${atrr}=#{attrVal} ")
public Map queryByTableNameAndAtrr(@Param("tableName") String tableName,@Param("id") String id,@Param("val") String val,@Param("atrr") String atrr,@Param("attrVal") String attrVal);
@Update("update ${tableName} set ${updateAttr}=#{updateAttrVal} where ${condition}=#{conditionVal}")
public void updateByTableNameAndAttr(@Param("tableName") String tableName,@Param("condition") String condition,@Param("conditionVal") String conditionVal,@Param("updateAttr") String updateAttr,@Param("updateAttrVal") String updateAttrVal);
}
测试:
@RunWith(SpringRunner.class)
@MapperScan("com.example.demo")
@SpringBootTest
public class DemoApplicationTests {
@Autowired
UpdateResposity resposity;
@Test
public void contextLoads() {
Map ob =resposity.queryByTableNameAndAtrr("ta","id","name","id","1");
if(ob!=null){
String name=ob.get("val")+"hello ";
System.out.println(ob.get("id"));
resposity.updateByTableNameAndAttr("ta","id",ob.get("id")+""
,"name",name);
}
System.out.println(ob);
}
}
1.2使用xml配置文件方式:
pom.xml
org.mybatis.spring.boot
mybatis-spring-boot-starter
1.3.2
tk.mybatis
mapper-spring-boot-starter
1.1.7
mysql
mysql-connector-java
runtime
org.springframework.boot
spring-boot-starter-web
org.springframework.boot
spring-boot-starter-test
test
mapper接口:
/**
* Author: hezishan
* Date: 2018/7/12.
* Description:
**/
public interface TMapper {
Map selectByTableNameAndPrimaryAttr(@Param("tableName") String tableName,@Param("conditions")List conditions);
List
mapper.xml
update ${tableName} set
${change.attr}= #{change.value}
${condition.attr}=${condition.value}
condition类:存放属性、属性值
/**
* Author: hezishan
* Date: 2018/7/12.
* Description:
**/
public class Condition {
private String attr;
private String opera;
private Object value; //get set}
测试:
public String update() {
List list=new ArrayList();
Condition condition=new Condition();
condition.setAttr("id");
condition.setValue(1);
list.add(condition);
Map map=tMapper.selectByTableNameAndPrimaryAttr("ta",list);
if(map!=null){
List changeList=new ArrayList();
Condition cond=new Condition();
cond.setAttr("name");
cond.setValue("hello world");
changeList.add(cond);
tMapper.updateByTableName("ta",changeList,list);
}
return "success" ;
}
通过上面的简单例子可以看出,使用xml配置方式能够指定多参数,适用范围为大。
提供mybatis带通用mapper逆向工程:https://github.com/hzsbrave/mybatisgenerator.git