# 第三节打基础

# 1、demo10-base-util

# ①ImperialCourtConst 常量类

public class ImperialCourtConst {

    public static final String LOGIN_FAILED_MESSAGE = "账号、密码错误，不可进宫！";
    public static final String ACCESS_DENIED_MESSAGE = "宫闱禁地，不得擅入！";

}

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# ②字符串加密工具类

public class MD5Util {

    /**
     * 针对明文字符串执行MD5加密
     * @param source
     * @return
     */
    public static String encode(String source) {

        // 1.判断明文字符串是否有效
        if (source == null || "".equals(source)) {
            throw new RuntimeException("用于加密的明文不可为空");
        }

        // 2.声明算法名称
        String algorithm = "md5";

        // 3.获取MessageDigest对象
        MessageDigest messageDigest = null;
        try {
            messageDigest = MessageDigest.getInstance(algorithm);
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }

        // 4.获取明文字符串对应的字节数组
        byte[] input = source.getBytes();

        // 5.执行加密
        byte[] output = messageDigest.digest(input);

        // 6.创建BigInteger对象
        int signum = 1;
        BigInteger bigInteger = new BigInteger(signum, output);

        // 7.按照16进制将bigInteger的值转换为字符串
        int radix = 16;
        String encoded = bigInteger.toString(radix).toUpperCase();

        return encoded;
    }

}

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# ③登录失败异常

public class LoginFailedException extends RuntimeException {

    public LoginFailedException() {
    }

    public LoginFailedException(String message) {
        super(message);
    }

    public LoginFailedException(String message, Throwable cause) {
        super(message, cause);
    }

    public LoginFailedException(Throwable cause) {
        super(cause);
    }

    public LoginFailedException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }
}

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# ④远程方法调用统一返回结果

/**
 * 统一整个项目中远程方法调用返回的结果
 * @author Lenovo
 *
 * @param <T>
 */
public class ResultEntity<T> {
	
	public static final String SUCCESS = "SUCCESS";
	public static final String FAILED = "FAILED";
	
	// 用来封装当前请求处理的结果是成功还是失败
	private String result;
	
	// 请求处理失败时返回的错误消息
	private String message;
	
	// 要返回的数据
	private T data;
	
	/**
	 * 请求处理成功且不需要返回数据时使用的工具方法
	 * @return
	 */
	public static <Type> ResultEntity<Type> successWithoutData() {
		return new ResultEntity<Type>(SUCCESS, null, null);
	}
	
	/**
	 * 请求处理成功且需要返回数据时使用的工具方法
	 * @param data 要返回的数据
	 * @return
	 */
	public static <Type> ResultEntity<Type> successWithData(Type data) {
		return new ResultEntity<Type>(SUCCESS, null, data);
	}
	
	/**
	 * 请求处理失败后使用的工具方法
	 * @param message 失败的错误消息
	 * @return
	 */
	public static <Type> ResultEntity<Type> failed(String message) {
		return new ResultEntity<Type>(FAILED, message, null);
	}
	
	public ResultEntity() {
		
	}

	public ResultEntity(String result, String message, T data) {
		super();
		this.result = result;
		this.message = message;
		this.data = data;
	}

	@Override
	public String toString() {
		return "ResultEntity [result=" + result + ", message=" + message + ", data=" + data + "]";
	}

	public String getResult() {
		return result;
	}

	public void setResult(String result) {
		this.result = result;
	}

	public String getMessage() {
		return message;
	}

	public void setMessage(String message) {
		this.message = message;
	}

	public T getData() {
		return data;
	}

	public void setData(T data) {
		this.data = data;
	}

}

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# 2、demo09-base-entity

# ①引入依赖

<dependency>
    <groupId>javax.persistence</groupId>
    <artifactId>persistence-api</artifactId>
</dependency>

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# ②创建实体类

在 MySQL 数据提供服务中用到的通用 Mapper 技术需要借助 @Table 注解将实体类和数据库表关联起来。

@Table(name = "t_emp")
public class Emp implements Serializable {

    private Integer empId;

    private String empName;

    private String empPosition;

    private String loginAccount;

    private String loginPassword;

    public Integer getEmpId() {
        return empId;
    }

    public void setEmpId(Integer empId) {
        this.empId = empId;
    }

    public String getEmpName() {
        return empName;
    }

    public void setEmpName(String empName) {
        this.empName = empName == null ? null : empName.trim();
    }

    public String getEmpPosition() {
        return empPosition;
    }

    public void setEmpPosition(String empPosition) {
        this.empPosition = empPosition == null ? null : empPosition.trim();
    }

    public String getLoginAccount() {
        return loginAccount;
    }

    public void setLoginAccount(String loginAccount) {
        this.loginAccount = loginAccount == null ? null : loginAccount.trim();
    }

    public String getLoginPassword() {
        return loginPassword;
    }

    public void setLoginPassword(String loginPassword) {
        this.loginPassword = loginPassword == null ? null : loginPassword.trim();
    }
}

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# 第三节 打基础