[学习交流] 模拟Mybatis逆向工程创建javaBean类：使用数据库的表来分别...

之前学习过Mybatis框架，记忆最深的还是逆向工程，模拟这个实现一些简单的小功能

思路：查询数据库所有表的结构，封装成对象遍历，来无脑拼出bean类。

主要功能：

startTables()数据库下所有表创建bean类
startTable(String tablename)根据指定表创建bean类

测试类：

运行之后会在bean包下创建相应的Bean类

以下为实现代码
Table类：
package com.field;

public class Table {
private String Field;
private String Type;
private String Null;
private String Key;
private String Default;
private String Extra;

public Table() {
}

public Table(String field, String type, String aNull, String key, String aDefault, String extra) {
      Field = field;
      Type = type;
      Null = aNull;
      Key = key;
      Default = aDefault;
      Extra = extra;
}

public String getField() {
      return Field;
}

public void setField(String field) {
      Field = field;
}

public String getType() {
      return Type;
}

public void setType(String type) {
      Type = type;
}

public String getNull() {
      return Null;
}

public void setNull(String aNull) {
      Null = aNull;
}

public String getKey() {
      return Key;
}

public void setKey(String key) {
      Key = key;
}

public String getDefault() {
      return Default;
}

public void setDefault(String aDefault) {
      Default = aDefault;
}

public String getExtra() {
      return Extra;
}

public void setExtra(String extra) {
      Extra = extra;
}
}
Reverse类：
package com.util;

import com.field.Table;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class Reverse {
private DBCon dbc;

//创建对象时初始画一个数据连接
public Reverse() {
      dbc = new DBCon();
}

/**
   * 获取对应数据库的所有表
   */
private List<String> getTables() {
      ArrayList<String> list = new ArrayList<>();
      String sql = "show tables";
      ResultSet rs = dbc.doQuery(sql, new Object[]{});
      try {
         while (rs.next()) {
            list.add(rs.getString(1));
         }
      } catch (SQLException e) {
         e.printStackTrace();
      }
      return list;
}

/**
   * 判断输入的表是否存在
   *
   * @param tablename
   * @return
   */
private boolean isTableExists(String tablename) {
      List<String> list = getTables();
      return list.contains(tablename);

}

/**
   * 封装存储表的字段
   *
   * @param tablename
   * @return
   */
private ArrayList<Table> getDesc(String tablename) {
      if (isTableExists(tablename)) {
         String sql = "desc " + tablename;
         ResultSet rs = dbc.doQuery(sql, new Object[]{});
         ArrayList<Table> list = new ArrayList<>();
         try {
            while (rs.next()) {
                  Table table = new Table();
                  table.setField(rs.getString("Field"));
                  table.setType(rs.getString("Type"));
                  table.setNull(rs.getString("Null"));
                  table.setKey(rs.getString("Key"));
                  table.setDefault(rs.getString("Default"));
                  table.setExtra(rs.getString("Extra"));
                  list.add(table);
            }
         } catch (SQLException e) {
            e.printStackTrace();
         }
         return list;
      }
      throw new RuntimeException("表不存在！");
}

/**
   * 创建对应数据库所有的表
   */
public void startTables() {
      List<String> tables = getTables();
      for (String table : tables) {
         startTable(table);
      }
}

/**
   * 单个表的创建
   *
   * @param tablename
   */
public void startTable(String tablename) {
      PrintWriter pw = null;
      try {
         //创建打印流，和指定打印路径
         pw = new PrintWriter(new FileWriter(getPath("MyHibernate03") + toUpper(tablename) + ".java"));
      } catch (IOException e) {
         e.printStackTrace();
      }
      StringBuilder sb = new StringBuilder();

      //包名注解
      pw.println("package com.bean;");
      pw.println();
      pw.println("import com.annoction.TableName;");
      pw.println("import com.annoction.Column;");
      pw.println("import com.annoction.Primarykey;");
      pw.println();
      pw.println("@TableName(\"" + tablename + "\")");
      pw.println("public class " + toUpper(tablename) + " {");
      ArrayList<Table> tables = getDesc(tablename);

      //成员变量和注解
      for (Table table : tables) {
         String type = changetype(table.getType());
         String filed = table.getField();
         if (getPrimaryKey(tablename).equals(filed)) {
            pw.print("\t");
            pw.println("@Primarykey(\"" + filed + "\")");
         }
         pw.print("\t");
         pw.println("@Column(\"" + filed + "\")");
         pw.print("\t");
         pw.println("private " + type + " " + filed + ";");
      }
      pw.println();
      //无参构造
      pw.println("public " + toUpper(tablename) + "(){}\r\n");
      pw.println();

      //全参构造
      pw.print("public " + toUpper(tablename) + "(");
      for (Table table : tables) {
         String field = table.getField();
         String type = changetype(table.getType());
         sb.append(type + " " + field + ",");
      }
      String substring = sb.substring(0, sb.length() - 1);
      pw.print(substring);
      pw.println(") {");
      for (Table table : tables) {
         String field = table.getField();
         pw.println("this." + field + "=" + field + ";");
      }
      pw.println("}");
      pw.println();

      //set/get方法
      for (Table table : tables) {
         String type = changetype(table.getType());
         String field = table.getField();
         pw.println("public void set" + toUpper(field) + "(" + type + " " + field + ") {");
         pw.println("this." + field + "=" + field + ";");
         pw.println("}");
         pw.println("public " + type + " get" + toUpper(field) + "(){");
         pw.println("return " + field + ";");
         pw.println("}");
         pw.println();
      }
      pw.println();

      //toString()
      pw.println("@Override");
      pw.println("public String toString(){");
      pw.println(" return \"" + toUpper(tablename) + "{\" +");
      sb = new StringBuilder();
      for (Table table : tables) {
         sb.append("  \"" + table.getField() + "=\" + " + table.getField() + "+\n" +
                  " \", \"+");
      }
      String str = sb.substring(0, sb.length() - 5).concat("\"}\"").concat(";");

      pw.println(str);
      pw.println("}");
      pw.println("}");
      pw.close();
}

/**
   * 拼接创建路径
   *
   * @return
   */
private String getPath(String projectname) {
      String path = DBCon.class.getClassLoader().getResource("db.properties").getPath();
      String sub1 = path.substring(1, path.length() -29-projectname.length());
      String sub2=sub1.concat(projectname).concat("/src/com/bean/");
      File file = new File(sub2);
      if (!file.exists()) file.mkdirs();
      return sub2;
}

/**
   * 获取主键名称
   *
   * @param tablename
   * @return
   */
private String getPrimaryKey(String tablename) {
      ArrayList<Table> desc = getDesc(tablename);
      for (Table table : desc) {
         if (table.getKey().equals("PRI")) {
            return table.getField();
         }

      }
      throw new RuntimeException("没有找到主键！");
}

/**
   * 类型转换
   *
   * @param type
   * @return
   */
private String changetype(String type) {
      if (type.startsWith("int")) return "int";
      if (type.startsWith("varchar")) return "String";
//       if(type.startsWith(""))
      else return "String";
}

private String toUpper(String str) {
      return String.valueOf(Character.toUpperCase(str.charAt(0))).concat(str.substring(1));
}

/**
   * 释放资源
   */
public void close() {
      dbc.close();
}

}
db.properties(放在src下)
driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/myhibernate?serverTimezone=UTC
username=root
password=123456
database=myhibernate

DBCon类：
package com.util;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class DBCon {
private static Properties prop;
private Connection conn;
private ResultSet rs;
private PreparedStatement pstmt;

public DBCon() {
      this.conn = getConn();
}

/**
   * 加载配置文件
   */
static {
      //获取配置文件的属性
      prop = new Properties();
      InputStream is = DBCon.class.getClassLoader().getResourceAsStream("db.properties");
      try {
         prop.load(is);
      } catch (IOException e) {
         e.printStackTrace();
      }
}

/**
   * 获取数据库连接
   *
   * @return
   */
public Connection getConn() {
      try {
         Class.forName(prop.getProperty("driver"));
         conn = DriverManager.getConnection(prop.getProperty("url"), prop.getProperty("username"), prop.getProperty("password"));
      } catch (Exception e) {
         e.printStackTrace();
      }
      return conn;
}

/**
   * 封装查询
   *
   * @param sql
   * @param arrs
   * @return
   */
public ResultSet doQuery(String sql, Object[] arrs) {
      //  rs = null;
      try {
         pstmt = conn.prepareStatement(sql);
         for (int i = 0; i < arrs.length; i++) {
            pstmt.setObject((i + 1), arrs[i]);
         }
         rs = pstmt.executeQuery();
      } catch (SQLException e) {
         e.printStackTrace();
      }
      return rs;
}

/**
   * 封装增删改
   *
   * @param sql
   * @param arrs
   * @return
   */
public int doUpdate(String sql, Object[] arrs) {
      int res = 0;
      try {
         pstmt = conn.prepareStatement(sql);
         for (int i = 0; i < arrs.length; i++) {
            pstmt.setObject((i + 1), arrs[i]);
         }
         res = pstmt.executeUpdate();
      } catch (SQLException e) {
         e.printStackTrace();
      }
      return res;
}

/**
   * 开启事务
   */
public void OpenTransaction() {
      try {
         //开启事务
         conn.setAutoCommit(false);
      } catch (SQLException e) {
         e.printStackTrace();
      }

}

/**
   * 提交事务
   */
public void commit() {
      try {
         conn.commit();
      } catch (SQLException e) {
         e.printStackTrace();
      }

}

/**
   * 回滚事务
   */
public void rollback() {
      try {
         conn.rollback();
      } catch (SQLException e) {
         e.printStackTrace();
      }
}

/**
   * 关闭资源
   */
public void close() {
      if (rs != null) {
         try {
            rs.close();
         } catch (SQLException e) {
            e.printStackTrace();
         }
      }
      if (pstmt != null) {
         try {
            pstmt.close();
         } catch (SQLException e) {
            e.printStackTrace();
         }
      }
      if (conn != null) {
         try {
            conn.close();
         } catch (SQLException e) {
            e.printStackTrace();
         }
      }
}

}

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[学习交流] 模拟Mybatis逆向工程创建javaBean类：使用数据库的表来分别...

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