REST API 中的 Java 空指针异常

Question

我实际上正在使用 postman 向我的 REST API 发送登录请求，但它给了我一个 javaNullpointer 异常。这是因为在模型类中我的变量之一没有获得值。我的模型类中未调用 setPhone_Number() 函数。因此 phone_number 变量为空。

感谢帮助。

这是我的错误屏幕截图 eclipse error for null pointer 这是我通过 postman 发送的内容 Postman

这是登录 dao 类。

 public class LoginDao {

 private String password;
 private String phone_number;


    public LoginDao(){
        phone_number = null;
        password = null;
    }

    public Response doLogin(login logg, String user_type) throws SQLException{
        ResultSet rs = null;
        boolean userType = true;        
        //if userType is resource then boolean is false, if userType is user then boolean is true.
        //logg.setPhone_Number(phone_number);

        DBConnection dbConnection = new DBConnection();
        //Connection connection = dbConnection.getConnection();
        this.phone_number = logg.getPhone_Number();
        this.password = logg.getPassword();


        try{
            if(user_type.equalsIgnoreCase("Rider")) {
                rs = dbConnection.runSql("select rider_id, phone_number, password from rider");
                userType = true;

            }
            else if(user_type.equalsIgnoreCase("Driver")) {
                rs = dbConnection.runSql("select driver_id, phone_number, password from driver");   
                userType = false;
            }

            while(rs.next()){
                System.out.println(phone_number);
                System.out.println(rs.getString("phone_number"));
                System.out.println("user"+user_type);

                if((this.phone_number.equals(rs.getString("phone_number"))) && (this.password.equals(rs.getString("password")))){

这是模型类登录

 public class login {

private String phone_number;
private String password;

public login(){

}

public String getPhone_Number() {

    System.out.println("getting "+phone_number);
    return phone_number;
}

public void setPhone_Number(String phone_number) {

    System.out.println("seting "+phone_number);
    this.phone_number = phone_number;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {

    System.out.println("seting "+password);
    this.password = password;
}

}

这是loginResource.java

 import javax.ws.rs.POST;

 import javax.ws.rs.Path;
 import javax.ws.rs.Produces;
 import javax.ws.rs.QueryParam;
 import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.Response;

 import static javax.ws.rs.core.MediaType.APPLICATION_JSON;

 import java.sql.SQLException;

  import javax.ws.rs.Consumes;

  import io.github.yasirfaisal21.schoolvan.schoolvan.dao.LoginDao;
 import io.github.yasirfaisal21.schoolvan.schoolvan.model.login;

  @Path("login")


 public class loginResource {
@Produces(MediaType.APPLICATION_JSON)
@Consumes(APPLICATION_JSON)
@POST
public Response doLogin(login log,@QueryParam("user_type") String user_type ) 
        throws SQLException{


LoginDao loginDao = new LoginDao();
if(user_type.equalsIgnoreCase("Rider"))
        return loginDao.doLogin(log,"Rider");
else
    return loginDao.doLogin(log,"Driver");
 }

}

Answer 1

在您的 login.java 类中，替换:

private String Phone_number;
与
私有(private)字符串电话号码；

并按照如下方式更新其 getter 和 setter:

public String getPhoneNumber() {
    return phoneNumber;
}

public void setPhoneNumber(String phoneNumber) {
    this.phoneNumber = phoneNumber;
}