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利用JAVA反射,讀取數(shù)據(jù)庫表名,自動生成對應(yīng)實體類的操作

 更新時間:2020年08月22日 09:47:51   作者:保持丶零距離  
這篇文章主要介紹了利用JAVA反射,讀取數(shù)據(jù)庫表名,自動生成對應(yīng)實體類的操作,具有很好的參考價值,希望對大家有所幫助。一起跟隨小編過來看看吧

本代碼是利用java反射,讀取數(shù)據(jù)庫表自動根據(jù)表名生成實體類,數(shù)據(jù)庫采用老牌SQLSERVER 2000,驅(qū)動為JTDS,其他數(shù)據(jù)庫可根據(jù)情況自定修改。

代碼中包含了大部分數(shù)據(jù)庫類型與JAVA類型的轉(zhuǎn)換,少數(shù)未包含進去的會在生成代碼時打印出來,方面后期查找修改。

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.text.SimpleDateFormat;
import java.util.Date;
 
/**
 * 從數(shù)據(jù)庫表反射出實體類,自動生成實體類
 * 
 * @author Zero
 *
 */
public class SqlHelper {
	//基本數(shù)據(jù)配置
	private String packageOutPath = "com.xxx.entity.system";// 指定實體生成所在包的路徑
	private String authorName = "Zero";// 作者名字
	private String tablename = "xxx";// 表名
	private String[] colnames; // 列名數(shù)組
	private String[] colTypes; // 列名類型數(shù)組
	private String version = "V0.01"; // 版本
	private int[] colSizes; // 列名大小數(shù)組
	private boolean f_util = false; // 是否需要導入包java.util.*
	private boolean f_sql = false; // 是否需要導入包java.sql.*
	private boolean f_lang = false; // 是否需要導入包java.sql.*
	private String defaultPath = "/src/main/java/";
	// 數(shù)據(jù)庫連接
	private static final String URL = "jdbc:jtds:sqlserver://192.168.29.128:1433/xxx";
	private static final String NAME = "sa";
	private static final String PASS = "xxx";
	private static final String DRIVER = "net.sourceforge.jtds.jdbc.Driver";
 
	/*
	 * 構(gòu)造函數(shù)
	 */
	public SqlHelper() {
		// 創(chuàng)建連接
		Connection con;
		// 查要生成實體類的表
		String sql = "select * from " + tablename;
		PreparedStatement pStemt = null;
		try {
			try {
				Class.forName(DRIVER);
			} catch (ClassNotFoundException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			}
			con = DriverManager.getConnection(URL, NAME, PASS);
			pStemt = con.prepareStatement(sql);
			ResultSetMetaData rsmd = pStemt.getMetaData();
			int size = rsmd.getColumnCount(); // 統(tǒng)計列
			colnames = new String[size];
			colTypes = new String[size];
			colSizes = new int[size];
			for (int i = 0; i < size; i++) {
 
				colnames[i] = rsmd.getColumnName(i + 1);
				colTypes[i] = rsmd.getColumnTypeName(i + 1);
				//自動生成包配置
				
				
				// if (colTypes[i].equalsIgnoreCase("datetime")) {
				// f_util = true;
				// }
				if (colTypes[i].equalsIgnoreCase("image") || colTypes[i].equalsIgnoreCase("text")
						|| colTypes[i].equalsIgnoreCase("datetime") || colTypes[i].equalsIgnoreCase("time")
						|| colTypes[i].equalsIgnoreCase("date") || colTypes[i].equalsIgnoreCase("datetime2")) {
					f_sql = true;
				}
				// if (colTypes[i].equalsIgnoreCase("int")) {
				// f_lang = true;
				// }
				colSizes[i] = rsmd.getColumnDisplaySize(i + 1);
			}
 
			String content = parse(colnames, colTypes, colSizes);
 
			try {
				File directory = new File("");
				
				String path = this.getClass().getResource("").getPath();
 
				System.out.println(path);
				
				String outputPath = directory.getAbsolutePath() + this.defaultPath
						+ this.packageOutPath.replace(".", "/") + "/" + initcap(tablename) + ".java";
				System.out.println("執(zhí)行完畢,生成路徑為:"+outputPath);
				FileWriter fw = new FileWriter(outputPath);
				PrintWriter pw = new PrintWriter(fw);
				pw.println(content);
				pw.flush();
				pw.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
 
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			
		}
	}
 
	/**
	 * 功能:生成實體類主體代碼
	 * 
	 * @param colnames
	 * @param colTypes
	 * @param colSizes
	 * @return
	 */
	private String parse(String[] colnames, String[] colTypes, int[] colSizes) {
		StringBuffer sb = new StringBuffer();
		// 生成package包路徑
		sb.append("package " + this.packageOutPath + ";\r\n");
		// 判斷是否導入工具包
		if (f_util) {
			sb.append("import java.util.Date;\r\n");
		}
		if (f_sql) {
			sb.append("import java.sql.*;\r\n");
		}
		if (f_lang) {
			sb.append("import java.lang.*;\r\n");
		}
 
		sb.append("\r\n");
		// 注釋部分
		sb.append("  /**\r\n");
		sb.append("  * @文件名稱:" + this.tablename + ".java\r\n");
		sb.append("  * @創(chuàng)建時間:" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()) + "\r\n");
		sb.append("  * @創(chuàng) 建 人:" + this.authorName + " \r\n");
		sb.append("  * @文件描述:" + tablename + " 實體類\r\n");
		sb.append("  * @文件版本:" + this.version + " \r\n");
		sb.append("  */ \r\n");
		// 實體部分
		sb.append("\r\n\r\npublic class " + initcap(tablename) + "{\r\n");
		processAllAttrs(sb);// 屬性
		processAllMethod(sb);// get set方法
		sb.append("}\r\n");
 
		// System.out.println(sb.toString());
		return sb.toString();
	}
 
	/**
	 * 功能:生成所有屬性
	 * 
	 * @param sb
	 */
	private void processAllAttrs(StringBuffer sb) {
 
		for (int i = 0; i < colnames.length; i++) {
			sb.append("\tprivate " + sqlType2JavaType(colTypes[i]) + " " + colnames[i] + ";\r\n");
		} 
	}
 
	/**
	 * 功能:生成所有方法
	 * 
	 * @param sb
	 */
	private void processAllMethod(StringBuffer sb) {
 
		for (int i = 0; i < colnames.length; i++) {
			sb.append("\tpublic void set" + initcap(colnames[i]) + "(" + sqlType2JavaType(colTypes[i]) + " "
					+ colnames[i] + "){\r\n");
			sb.append("\tthis." + colnames[i] + "=" + colnames[i] + ";\r\n");
			sb.append("\t}\r\n");
			sb.append("\tpublic " + sqlType2JavaType(colTypes[i]) + " get" + initcap(colnames[i]) + "(){\r\n");
			sb.append("\t\treturn " + colnames[i] + ";\r\n");
			sb.append("\t}\r\n");
		} 
	}
 
	/**
	 * 功能:將輸入字符串的首字母改成大寫
	 * 
	 * @param str
	 * @return
	 */
	private String initcap(String str) {
 
		char[] ch = str.toCharArray();
		if (ch[0] >= 'a' && ch[0] <= 'z') {
			ch[0] = (char) (ch[0] - 32);
		}
 
		return new String(ch);
	}
 
	/**
	 * 功能:獲得列的數(shù)據(jù)類型
	 * 
	 * @param sqlType
	 * @return
	 */
	private String sqlType2JavaType(String sqlType) {
 
		if (sqlType.equalsIgnoreCase("bit")) {
			return "Boolean";
		} else if (sqlType.equalsIgnoreCase("decimal") || sqlType.equalsIgnoreCase("money")
				|| sqlType.equalsIgnoreCase("smallmoney") || sqlType.equalsIgnoreCase("numeric")
				|| sqlType.equalsIgnoreCase("bigint")) {
			return "Long";
		} else if (sqlType.equalsIgnoreCase("float")) {
			return "Double";
		} else if (sqlType.equalsIgnoreCase("int") || sqlType.equalsIgnoreCase("int identity")) {
			return "Integer";
		} else if (sqlType.equalsIgnoreCase("image") || sqlType.equalsIgnoreCase("varbinary(max)")
				|| sqlType.equalsIgnoreCase("varbinary") || sqlType.equalsIgnoreCase("udt")
				|| sqlType.equalsIgnoreCase("timestamp") || sqlType.equalsIgnoreCase("binary")) {
			return "Byte[]";
		} else if (sqlType.equalsIgnoreCase("nchar") || sqlType.equalsIgnoreCase("nvarchar(max)")
				|| sqlType.equalsIgnoreCase("nvarchar") || sqlType.equalsIgnoreCase("nvarchar(ntext)")
				|| sqlType.equalsIgnoreCase("uniqueidentifier") || sqlType.equalsIgnoreCase("xml")
				|| sqlType.equalsIgnoreCase("char") || sqlType.equalsIgnoreCase("varchar(max)")
				|| sqlType.equalsIgnoreCase("text") || sqlType.equalsIgnoreCase("varchar")) {
			return "String";
		} else if (sqlType.equalsIgnoreCase("real")) {
			return "Float";
		} else if (sqlType.equalsIgnoreCase("smallint") || sqlType.equalsIgnoreCase("tinyint")) {
			return "Short";
		} else if (sqlType.equalsIgnoreCase("date") || sqlType.equalsIgnoreCase("datetime")
				|| sqlType.equalsIgnoreCase("time") || sqlType.equalsIgnoreCase("datetime2")) {
			return "Date";
		} else {
			System.out.println("數(shù)據(jù)類型異常,類型為:" + sqlType);
		}
 
		return null;
	}
 
	/**
	 * 出口 TODO
	 * 
	 * @param args
	 */
	public static void main(String[] args) {
 
		new SqlHelper();
 
	}
}

補充知識:java通過反射獲取類名、屬性名稱以及@Table注解上的表名稱

我就廢話不多說了,大家還是直接看代碼吧~

import javax.persistence.Column;
import javax.persistence.Id;
import javax.persistence.Table;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
 
/**
 * @author caizw
 * @createDate 2018/2/8
 * @description 反射工具類
 */
public class ReflectUtils {
 
  /**
   * 獲取實體類主鍵
   *
   * @param clazz
   * @return
   */
  public static Field getIdField(Class<?> clazz) {
    Field[] fields = clazz.getDeclaredFields();
    Field item = null;
    for (Field field : fields) {
      Id id = field.getAnnotation(Id.class);
      if (id != null) {
        field.setAccessible(true);
        item = field;
        break;
      }
    }
    if (item == null) {
      Class<?> superclass = clazz.getSuperclass();
      if (superclass != null) {
        item = getIdField(superclass);
      }
    }
    return item;
  }
 
  /**
   * 根據(jù)主鍵名稱獲取實體類主鍵屬性值
   *
   * @param clazz
   * @param pkName
   * @return
   */
  public static Object getPkValueByName(Object clazz, String pkName) {
    try {
      String firstLetter = pkName.substring(0, 1).toUpperCase();
      String getter = "get" + firstLetter + pkName.substring(1);
      Method method = clazz.getClass().getMethod(getter, new Class[]{});
      Object value = method.invoke(clazz, new Object[]{});
      return value;
    } catch (Exception e) {
      return null;
    }
  }
 
  /**
   * 通過反射將 class1不為空的值賦值給class2
   *
   * @param class1
   * @param class2
   * @throws Exception
   */
  public static void reflectClass1ToClass2(Object class1, Object class2) throws Exception {
    Field[] field = class1.getClass().getDeclaredFields();
    for (int i = 0; i < field.length; i++) {
      String name = field[i].getName();
      if ("serialVersionUID".equals(name)) {
        continue;
      }
      name = name.substring(0, 1).toUpperCase() + name.substring(1);
      Method m1 = class1.getClass().getMethod("get" + name);
      Object value = m1.invoke(class1);
      if (value != null) {
        Field f = field[i];
        f.setAccessible(true);
        f.set(class2, value);
      }
    }
  }
 
  /**
   * 獲取實體類 @Column 的其中一個屬性名稱
   *
   * @param clazz
   * @return
   */
  public static Map<String, String> getColumnName(Class<?> clazz) {
    Map<String, String> map = new ConcurrentHashMap<>();
    Field[] fields = clazz.getDeclaredFields();
    for (Field field : fields) {
      if (field.isAnnotationPresent(Column.class)) {
        /**
         * 獲取字段名
         */
        Column declaredAnnotation = field.getDeclaredAnnotation(Column.class);
        String column = declaredAnnotation.name();
        map.put("fieldNames", field.getName());
        map.put("column", column);
        break;
      }
    }
    return map;
  }
 
  /**
   * 通過獲取類上的@Table注解獲取表名稱
   *
   * @param clazz
   * @return
   */
  public static Map<String, String> getTableName(Class<?> clazz) {
    Map<String, String> map = new ConcurrentHashMap<>();
    Table annotation = clazz.getAnnotation(Table.class);
    String name = annotation.name();
    String className = clazz.getSimpleName();
    map.put("tableName", name);
    map.put("className", className);
    return map;
  }
}

以上這篇利用JAVA反射,讀取數(shù)據(jù)庫表名,自動生成對應(yīng)實體類的操作就是小編分享給大家的全部內(nèi)容了,希望能給大家一個參考,也希望大家多多支持腳本之家。

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