MyBatis使用 @SelectProvider、@InsertProvider、@UpdateProvider、@DeleteProvider注解 建动态SQL语句。
type属性，该属性指定一个类；method属性指定该类的方法，其用来提供需要执行的SQL语句


PetMapper.java
@SelectProvider(type= SqlProvider.class,method="queryPetsByStartId")
List< PetDO> queryPetsByStartIdIfIdNotNull2(PetDO pet);

public class SqlProvider {
    public String queryPetsByStartId(PetDO pet){
        String sql = "SELECT id,name,age FROM pet ";
        Long id = null;
        if(pet!=null) {
            id = pet.getId();
        }
        if(id!=null && id>0){
            sql = sql + " where id=#{id} ";
        }
        sql = sql + " order by id asc";
        return sql;
    }
}



    @RequestMapping("/queryPetsByStartIdIfIdNotNull2")
    public Object queryPetsByStartIdIfIdNotNull2(@RequestParam long id){
        PetDO pet = new PetDO();
        if(id>0){
            pet.setId(id);
        }
        return petMapper.queryPetsByStartIdIfIdNotNull2(pet);
    }


查看 sql 信息的工具 



    @RequestMapping("/getMappedStatementNames")
    public Object getMappedStatementNames(){
        return sqlSessionFactory.getConfiguration().getMappedStatementNames();
    }

    @RequestMapping("/getSqlSource")
    public Object getSqlSource(String id)throws Exception{

        Configuration config = sqlSessionFactory.getConfiguration();
        MappedStatement mappedStatement = config.getMappedStatement(id);
        if(mappedStatement==null){
            return "mappedStatement_null";
        }
        SqlSource sqlSource = mappedStatement.getSqlSource();
        Map map = new HashMap<>();
        map.put("type",sqlSource.getClass().toString());
        map.put("info",sqlSource.toString());
        
        return map;
    }

    @RequestMapping("/getBoundSql")
    public Object getBoundSql(String id)throws Exception{

        Configuration config = sqlSessionFactory.getConfiguration();
        MappedStatement mappedStatement = config.getMappedStatement(id);
        if(mappedStatement==null){
            return "mappedStatement_null";
        }
        SqlSource sqlSource = mappedStatement.getSqlSource();
        return sqlSource.getBoundSql(null);
    }

    @RequestMapping("/getBoundSql2")
    public Object getBoundSql2(String id,long petId)throws Exception{

        Configuration config = sqlSessionFactory.getConfiguration();
        MappedStatement mappedStatement = config.getMappedStatement(id);
        if(mappedStatement==null){
            return "mappedStatement_null";
        }
        SqlSource sqlSource = mappedStatement.getSqlSource();
        PetDO pet = null;new PetDO();
        if(petId>0) {
            pet = new PetDO();
            pet.setId(petId);
        }
        return sqlSource.getBoundSql(pet);
    }
}




http://127.0.0.1:8080/getSqlSource?id=org.demo.dao.mapper.PetMapper.queryPetsByStartIdIfIdNotNull2
{"type":"class org.apache.ibatis.builder.annotation.ProviderSqlSource","info":"org.apache.ibatis.builder.annotation.ProviderSqlSource@152789ae"}


http://127.0.0.1:8080/getBoundSql2?id=org.demo.dao.mapper.PetMapper.queryPetsByStartIdIfIdNotNull2&petId=0
{"sql":"SELECT id,name,age FROM pet  order by id asc","parameterMappings":[],"parameterObject":null}


http://127.0.0.1:8080/getBoundSql2?id=org.demo.dao.mapper.PetMapper.queryPetsByStartIdIfIdNotNull2&petId=1
{
  "sql": "SELECT id,name,age FROM pet  where id=?  order by id asc",
  "parameterMappings": [
    {
      "property": "id",
      "mode": "IN",
      "javaType": "java.lang.Long",
      "jdbcType": null,
      "numericScale": null,
      "typeHandler": {
        "rawType": "java.lang.Long"
      },
      "resultMapId": null,
      "jdbcTypeName": null,
      "expression": null
    }
  ],
  "parameterObject": {
    "id": 1,
    "name": null,
    "age": null
  }
}





https://gitee.com/dyyx/work2024/blob/master/demo/mybatis-paging-demo/src/main/java/org/demo/controller/HelloController.java