spring boot學習（四）之連接數據庫整合jdbcTemplate

添加數據庫依賴

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

在application.properties配置文件中配置數據源

spring.datasource.url = jdbc:mysql://localhost:3306/spring?useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8
spring.datasource.username = root
spring.datasource.password = 123456
spring.datasource.driver-class-name = com.mysql.cj.jdbc.Driver

添加數據池依賴，這裏用的是阿里巴巴的數據池

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.19</version>
        </dependency>

在啓動類Chapter1Application.java中讀取數據源配置信息，Spring Boot會自動的用我們配置的這個DataSource。添加如下代碼

    @Autowired
    private Environment environment;
    
    public DataSource dataSource(destroyMethod =  "close") {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setUrl(environment.getProperty("datasource.url"));
        dataSource.setUsername(environment.getProperty("datasource.username"));
        dataSource.setPassword(environment.getProperty("datasource.password"));
        dataSource.setDriverClassName(environment.getProperty("datasource.driver-class-name"));
        dataSource.setInitialSize(5);//初始化時建立物理連接的個數
        dataSource.setMaxActive(20);//最大連接池數量
        dataSource.setMinIdle(0);//最小連接池數量
        dataSource.setMaxWait(50000);//獲取連接時最大等待時間，單位毫秒。
        dataSource.setValidationQuery("SELECT 1");//用來檢測連接是否有效的sql
        return dataSource;
    }

下面就用我們配置的這個數據源信息，用JdbcTemplate來與數據庫進行數據交互

本地創建spring數據庫，再創建一張user表，表屬性如下，自行填幾條數據：

簡單的做了個查詢的例子：

• 創建實體文件：User.java

public class User {
    private int id;
    private String name;
    private int age;
    private String address;
    private String phone;
    //set and get
}

• controller層：UserController.java:

@RestController
public class UserController {

    @Autowired
    private UserService userService;
    private Logger logger = LoggerFactory.getLogger(this.getClass());

    @RequestMapping(value = "/queryUserList",method = RequestMethod.GET,produces="application/json;charset=UTF-8")
    @ResponseBody
    public String queryLearnList(HttpServletRequest request , HttpServletResponse response){

        String name = request.getParameter("name");
        String phone = request.getParameter("phone");
        Map<String,Object> params = new HashMap<String,Object>();
        params.put("name", name);
        params.put("phone", phone);
        List userList =userService.queryUserList(params);
        return JSONArray.fromObject(userList).toString();

    }

• service層：接口UserService.java和實現類UserServiceImpl.java

public interface UserService {
    List queryUserList(Map<String, Object> params);
}

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    UserDao userDao;
    @Override
    public List queryUserList(Map<String,Object> params) {
        return userDao.queryUserList(params);
    }
}

• dao層：接口UserDao.java和實現類UserDaoImpl.java

public interface UserDao {
    public List queryUserList(Map<String, Object> params);

}

UserDaoImpl .java注入JdbcTemplate，spring boot會自動選擇我們配置好的數據源:

@Repository
public class UserDaoImpl implements UserDao{
    @Autowired
    private JdbcTemplate jdbcTemplate;//這裏直接引用即可
    @Override
    public List queryUserList(Map<String, Object> params) {
        StringBuffer sql =new StringBuffer();
        sql.append("select * from user where 1=1");
        if(!StringUtil.isNull((String)params.get("name"))){
            sql.append(" and name like '%").append((String)params.get("name")).append("%'");
        }
        if(!StringUtil.isNull((String)params.get("phone"))){
            sql.append(" and phone like '%").append((String)params.get("phone")).append("%'");
        }
        List<User> list = jdbcTemplate.query(sql.toString(),new BeanPropertyRowMapper(User.class));
        return list;
    }
}

結果

運行項目，瀏覽器輸入：http://localhost:8080/queryUserList，得到如下結果

總結

在此實踐過程可能會出現以下問題：

第一個錯誤

報錯信息:

原因：項目打了jar包，一旦運行就會有兩個啓動類，指定其中一個即可
解決辦法：在pom.xml的plugin下面添加如下配置即可

<configuration>
    <mainClass>com.mlin.ChapterApplication</mainClass>
</configuration>

第二個錯誤

報錯信息：

java.sql.SQLException: The server time zone value 'Öйú±ê׼ʱ¼ä' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.

原因：沒有配置時區信息
解決辦法：在配置數據源的時候加上serverTimezone=GMT%2B8

datasource.url = jdbc:mysql://localhost:3306/spring?useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8

第三個錯誤

報錯信息：就是在用到return JSONArray.fromObject(userList).toString();時，引入net.sf.json-lib依賴一直引入不進去
原因：要指定jdk
解決辦法：加入<classifier>jdk15</classifier>即可,但是改成jdk8或是jdk7不行：

       <dependency>
            <groupId>net.sf.json-lib</groupId>
            <artifactId>json-lib</artifactId>
            <version>2.4</version>
            <classifier>jdk15</classifier>
        </dependency>

原創作者：夢凌小樣
作品鏈接：https://www.jianshu.com/p/45eb56f448ae【原創不易，轉載請註明出處，感謝理解】
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