spring boot jdbcTemplate簡單查詢的使用

本文參考自: https://blog.csdn.net/chenyezhou1/article/details/71122570

(1)基礎的查詢操作，因爲jdbcTemplate不像mybatis那種有對應的映射關係，因此操作實體，需要手寫函數

class UserRowMapper implements RowMapper<User> {
             public User mapRow(ResultSet rs, int rowNum) throws SQLException {
                 User user = new User();
                 user.setId(rs.getInt("id"));
                 user.setName(rs.getString("name"));
                 user.setGender(rs.getString("gender"));
                 return user;
             }
 }

(2)如果想直接返回實體，可以配置RowMapper通用類

public class GenericMapper implements RowMapper<Map<String, String>> {
    @Override
    public Map<String, String> mapRow(ResultSet rs, int index) throws SQLException {
        ResultSetMetaData metaData = rs.getMetaData();
        int columnCount = metaData.getColumnCount();
        Map<String, String> map = new HashMap<>(8);
        for (int i = 1; i <= columnCount; i++) {
            // System.out.println("columnName:" + metaData.getColumnName(i)); 與下方的返回值相同
            //  System.out.println("columnLabel:" + metaData.getColumnLabel(i));
            String columnName = metaData.getColumnName(i);
            String value = rs.getString(columnName);
            if (value == null || " ".equals(value)) {
                //這裏是將爲null或者" "的列數據賦值爲""，可以按不同的需求進行更改
                value = "";
            } else {
                value = rs.getString(columnName);
            }
            map.put(columnName, value);
        }
        return map;
    }
}

用的時候直接調用即可，這裏我爲了方便直接寫在了controller層

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.cpicdg.dc.datacauser.util.GenericMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * @program: datacauser
 * @description: 數據控制層，目前就是單純的數據給出接口，邏輯直接寫在controller層
 * @author: zyy
 * @create: 2020-03-31 10:56
 **/
@RestController
@RequestMapping("/outData")
public class DataController {
    private Logger logger = LoggerFactory.getLogger(this.getClass());
    private final JdbcTemplate jdbcTemplate;
    
    @Autowired
    public DataController(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    @GetMapping
    public String getData() {
        String sql = "select * from sys.sys_config;";
        List<Map<String, String>> query = jdbcTemplate.query(sql, new GenericMapper());
        logger.info(JSON.toJSONString(query));
        return JSONObject.toJSONString(query);
    }
}