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我们在之前的实现了springboot与data-jpa的增、删、改、查简单使用（请戳：），并实现了升级版（请戳：），在基础版、升级版中，我们实现了单表的基础get、save（插入/更新）、list、page、delete接口，并写了一套通用common代码，每个单表去继承从而实现这套基础接口、同时，我们使用用Vo去接收、传输数据，实体负责与数据库表映射。
但是，单表增、删、改、查基础功能相似，代码高度相似，我们新增一个单表操作的步骤：复制、粘贴、修改文件夹、文件名、类名、修改传参实体对象...，为了实现快速开发，我们在前面两个版本的基础上，使用代码自动生成一套单表的基础增、删、改、查接口
首先我们先创建一个新的工程项目，实现一套common代码，以便单表直接继承
CodeDOM.java是一个比较大的类，因为我把所有的东西都丢在了里面...，接下来我们拆分讲解一下步骤（文末贴出CodeDOM.java完整代码）
首先定义几个属性，构造函数传入表名，基础路径基于表名进行赋值
/** * 表名 */ private String tableName; /** * 基础路径 */ private String basePackage_; private String package_; private String basePath;
构造函数
/** * 构造参数，出入表名 */ private CodeDOM(String tableName) { this.tableName = tableName; basePackage_ = "cn\\huanzi\\springbootjpa\\"; package_ = basePackage_ + StringUtil.camelCaseName(tableName).toLowerCase() + "\\"; //System.getProperty("user.dir") 获取的是项目所在路径，如果我们是子项目，则需要添加一层路径 basePath = System.getProperty("user.dir") + "\\src\\main\\java\\" + package_; }
首先要连接数据库，连接数据使用jdbc进行连接
/** * 数据连接相关 */ private static final String URL = "jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8&characterEncoding=utf-8"; private static final String USERNAME = "root"; private static final String PASSWORD = "123456"; private static final String DRIVERCLASSNAME = "com.mysql.jdbc.Driver";
/** * JDBC连接数据库工具类 */ private static class DBConnectionUtil { static { // 1、加载驱动 try { Class.forName(DRIVERCLASSNAME); } catch (ClassNotFoundException e) { e.printStackTrace(); } } /** * 返回一个Connection连接 * * @return */ public static Connection getConnection() { Connection conn = null; // 2、连接数据库 try { conn = DriverManager.getConnection(URL, USERNAME, PASSWORD); } catch (SQLException e) { e.printStackTrace(); } return conn; } /** * 关闭Connection，Statement连接 * * @param conn * @param stmt */ public static void close(Connection conn, Statement stmt) { try { conn.close(); stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } /** * 关闭Connection，Statement，ResultSet连接 * * @param conn * @param stmt * @param rs */ public static void close(Connection conn, Statement stmt, ResultSet rs) { try { close(conn, stmt); rs.close(); } catch (SQLException e) { e.printStackTrace(); } } } 获取数据表的表机构信息（本系列用的是MySQL数据库），通过查询 information_schema 表，SQL：
select column_name,data_type,column_comment,column_key,extra from information_schema.columns where table_schema = (select database()) and table_name=?
创建一个表结构对象，然后封装一下方法：
/** * 表结构行信息实体类 */ private class TableInfo { private String columnName; private String dataType; private String columnComment; private String columnKey; private String extra; TableInfo() { } String getColumnName() { return columnName; } void setColumnName(String columnName) { this.columnName = columnName; } String getDataType() { return dataType; } void setDataType(String dataType) { this.dataType = dataType; } String getColumnComment() { return columnComment; } void setColumnComment(String columnComment) { this.columnComment = columnComment; } String getColumnKey() { return columnKey; } void setColumnKey(String columnKey) { this.columnKey = columnKey; } String getExtra() { return extra; } void setExtra(String extra) { this.extra = extra; } } /** * 获取表结构信息 * * @return list */ private ListgetTableInfo() { Connection conn = null; PreparedStatement ps = null; ResultSet rs = null; ArrayList list = new ArrayList<>(); try { conn = DBConnectionUtil.getConnection(); String sql = "select column_name,data_type,column_comment,column_key,extra from information_schema.columns where table_schema = (select database()) and table_name=?"; ps = conn.prepareStatement(sql); ps.setString(1, tableName); rs = ps.executeQuery(); while (rs.next()) { TableInfo tableInfo = new TableInfo(); //列名，全部转为小写 tableInfo.setColumnName(rs.getString("column_name").toLowerCase()); //列类型 tableInfo.setDataType(rs.getString("data_type")); //列注释 tableInfo.setColumnComment(rs.getString("column_comment")); //主键 tableInfo.setColumnKey(rs.getString("column_key")); //主键类型 tableInfo.setExtra(rs.getString("extra")); list.add(tableInfo); } } catch (SQLException e) { e.printStackTrace(); } finally { assert rs != null; DBConnectionUtil.close(conn, ps, rs); } return list; }
2020-11-25更新
bug修复：修复代码生成工具类，不同库有相同表时，生成的实体类有重复字段的bug；查询表结构信息时，条件限定当前连接库即可：table_schema = (select database())
那么oracle应该怎么查呢？
--表结构信息select * from user_tab_columns where table_name='TB_USER'--表字段注释select * from user_col_comments where table_name='TB_USER'--表注释select * from user_tab_comments where table_name='TB_USER'
我们看一下系统都提供有哪些表，这...太多了
数据处理，比如数据字段类型转成java类型、字段的下划线转驼峰等，我们封装一下工具类：
/** * 字符串处理工具类 */ private static class StringUtil { /** * 数据库类型->JAVA类型 * * @param dbType 数据库类型 * @return JAVA类型 */ private static String typeMapping(String dbType) { String javaType = ""; if ("int|integer".contains(dbType)) { javaType = "Integer"; } else if ("float|double|decimal|real".contains(dbType)) { javaType = "Double"; } else if ("date|time|datetime|timestamp".contains(dbType)) { javaType = "Date"; } else { javaType = "String"; } return javaType; } /** * 驼峰转换为下划线 */ public static String underscoreName(String camelCaseName) { StringBuilder result = new StringBuilder(); if (camelCaseName != null && camelCaseName.length() > 0) { result.append(camelCaseName.substring(0, 1).toLowerCase()); for (int i = 1; i < camelCaseName.length(); i++) { char ch = camelCaseName.charAt(i); if (Character.isUpperCase(ch)) { result.append("_"); result.append(Character.toLowerCase(ch)); } else { result.append(ch); } } } return result.toString(); } /** * 首字母大写 */ public static String captureName(String name) { char[] cs = name.toCharArray(); cs[0] -= 32; return String.valueOf(cs); } /** * 下划线转换为驼峰 */ public static String camelCaseName(String underscoreName) { StringBuilder result = new StringBuilder(); if (underscoreName != null && underscoreName.length() > 0) { boolean flag = false; for (int i = 0; i < underscoreName.length(); i++) { char ch = underscoreName.charAt(i); if ("_".charAt(0) == ch) { flag = true; } else { if (flag) { result.append(Character.toUpperCase(ch)); flag = false; } else { result.append(ch); } } } } return result.toString(); } }
文件处理比如创建文件夹、文件，将字符写入文件等，我们先获取一下基础路径，并封装一下文件工具类：
/** * file工具类 */ private static class FileUtil { /** * 创建文件 * * @param pathNameAndFileName 路径跟文件名 * @return File对象 */ private static File createFile(String pathNameAndFileName) { File file = new File(pathNameAndFileName); try { //获取父目录 File fileParent = file.getParentFile(); if (!fileParent.exists()) { fileParent.mkdirs(); } //创建文件 if (!file.exists()) { file.createNewFile(); } } catch (Exception e) { file = null; System.err.println("新建文件操作出错"); e.printStackTrace(); } return file; } /** * 字符流写入文件 * * @param file file对象 * @param stringBuffer 要写入的数据 */ private static void fileWriter(File file, StringBuffer stringBuffer) { //字符流 try { FileWriter resultFile = new FileWriter(file, true);//true,则追加写入 false,则覆盖写入 PrintWriter myFile = new PrintWriter(resultFile); //写入 myFile.println(stringBuffer.toString()); myFile.close(); resultFile.close(); } catch (Exception e) { System.err.println("写入操作出错"); e.printStackTrace(); } } }
根据我们项目的路径规范，代码编写规范，我们定义好文件的模板，并封装成对应的方法
/** * 创建pojo实体类 */ private void createPojo(ListtableInfos) { File file = FileUtil.createFile(basePath + "pojo\\" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + ".java"); StringBuffer stringBuffer = new StringBuffer(); stringBuffer.append( "package " + package_.replaceAll("\\\\", ".") + "pojo;\n" + "\n" + "import lombok.Data;\n" + "import javax.persistence.*;\n" + "import java.io.Serializable;\n" + "import java.util.Date;\n" + "\n" + "@Entity\n" + "@Table(name = \"" + tableName + "\")\n" + "@Data\n" + "public class " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + " implements Serializable {\n" ); //遍历设置属性 for (TableInfo tableInfo : tableInfos) { //主键 if ("PRI".equals(tableInfo.getColumnKey())) { stringBuffer.append(" @Id\n"); } //自增 if ("auto_increment".equals(tableInfo.getExtra())) { stringBuffer.append(" @GeneratedValue(strategy= GenerationType.IDENTITY)\n"); } stringBuffer.append(" private " + StringUtil.typeMapping(tableInfo.getDataType()) + " " + StringUtil.camelCaseName(tableInfo.getColumnName()) + ";//" + tableInfo.getColumnComment() + "\n\n"); } stringBuffer.append("}"); FileUtil.fileWriter(file, stringBuffer); }
/** * 创建vo类 */ private void createVo(ListtableInfos) { File file = FileUtil.createFile(basePath + "vo\\" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Vo.java"); StringBuffer stringBuffer = new StringBuffer(); stringBuffer.append( "package " + package_.replaceAll("\\\\", ".") + "vo;\n" + "\n" + "import "+ basePackage_.replaceAll("\\\\", ".") +" common.pojo.PageCondition;"+ "import lombok.Data;\n" + "import java.io.Serializable;\n" + "import java.util.Date;\n" + "\n" + "@Data\n" + "public class " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Vo extends PageCondition implements Serializable {\n" ); //遍历设置属性 for (TableInfo tableInfo : tableInfos) { stringBuffer.append(" private " + StringUtil.typeMapping(tableInfo.getDataType()) + " " + StringUtil.camelCaseName(tableInfo.getColumnName()) + ";//" + tableInfo.getColumnComment() + "\n\n"); } stringBuffer.append("}"); FileUtil.fileWriter(file, stringBuffer); }
/** * 创建repository类 */ private void createRepository(ListtableInfos) { File file = FileUtil.createFile(basePath + "repository\\" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Repository.java"); StringBuffer stringBuffer = new StringBuffer(); String t = "String"; //遍历属性 for (TableInfo tableInfo : tableInfos) { //主键 if ("PRI".equals(tableInfo.getColumnKey())) { t = StringUtil.typeMapping(tableInfo.getDataType()); } } stringBuffer.append( "package " + package_.replaceAll("\\\\", ".") + "repository;\n" + "\n" + "import " + basePackage_.replaceAll("\\\\", ".") + "common.repository.*;\n" + "import " + package_.replaceAll("\\\\", ".") + "pojo." + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + ";\n" + "import org.springframework.stereotype.Repository;\n" + "\n" + "@Repository\n" + "public interface " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Repository extends CommonRepository<" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + ", " + t + "> {" ); stringBuffer.append("\n"); stringBuffer.append("}"); FileUtil.fileWriter(file, stringBuffer); }
/** * 创建service类 */ private void createService(ListtableInfos) { File file = FileUtil.createFile(basePath + "service\\" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Service.java"); StringBuffer stringBuffer = new StringBuffer(); String t = "String"; //遍历属性 for (TableInfo tableInfo : tableInfos) { //主键 if ("PRI".equals(tableInfo.getColumnKey())) { t = StringUtil.typeMapping(tableInfo.getDataType()); } } stringBuffer.append( "package " + package_.replaceAll("\\\\", ".") + "service;\n" + "\n" + "import " + basePackage_.replaceAll("\\\\", ".") + "common.service.*;\n" + "import " + package_.replaceAll("\\\\", ".") + "pojo." + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + ";\n" + "import " + package_.replaceAll("\\\\", ".") + "vo." + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Vo;\n" + "\n" + "public interface " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Service extends CommonService<" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Vo, " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + ", " + t + "> {" ); stringBuffer.append("\n"); stringBuffer.append("}"); FileUtil.fileWriter(file, stringBuffer); //Impl File file1 = FileUtil.createFile(basePath + "service\\" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "ServiceImpl.java"); StringBuffer stringBuffer1 = new StringBuffer(); stringBuffer1.append( "package " + package_.replaceAll("\\\\", ".") + "service;\n" + "\n" + "import " + basePackage_.replaceAll("\\\\", ".") + "common.service.*;\n" + "import " + package_.replaceAll("\\\\", ".") + "pojo." + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + ";\n" + "import " + package_.replaceAll("\\\\", ".") + "vo." + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Vo;\n" + "import " + package_.replaceAll("\\\\", ".") + "repository." + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Repository;\n" + "import org.springframework.beans.factory.annotation.Autowired;\n" + "import org.springframework.stereotype.Service;\n" + "import org.springframework.transaction.annotation.Transactional;\n" + "import javax.persistence.EntityManager;\n" + "import javax.persistence.PersistenceContext;\n" + "\n" + "@Service\n" + "@Transactional\n" + "public class " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "ServiceImpl extends CommonServiceImpl<" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Vo, " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + ", " + t + "> implements " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Service{" ); stringBuffer1.append("\n\n"); stringBuffer1.append( " @PersistenceContext\n" + " private EntityManager em;\n"); stringBuffer1.append("" + " @Autowired\n" + " private " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Repository " + StringUtil.camelCaseName(tableName) + "Repository;\n"); stringBuffer1.append("}"); FileUtil.fileWriter(file1, stringBuffer1); }
/** * 创建controller类 */ private void createController(ListtableInfos) { File file = FileUtil.createFile(basePath + "controller\\" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Controller.java"); StringBuffer stringBuffer = new StringBuffer(); String t = "String"; //遍历属性 for (TableInfo tableInfo : tableInfos) { //主键 if ("PRI".equals(tableInfo.getColumnKey())) { t = StringUtil.typeMapping(tableInfo.getDataType()); } } stringBuffer.append( "package " + package_.replaceAll("\\\\", ".") + "controller;\n" + "\n" + "import " + basePackage_.replaceAll("\\\\", ".") + "common.controller.*;\n" + "import " + package_.replaceAll("\\\\", ".") + "pojo." + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + ";\n" + "import " + package_.replaceAll("\\\\", ".") + "vo." + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Vo;\n" + "import " + package_.replaceAll("\\\\", ".") + "service." + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Service;\n" + "import org.springframework.beans.factory.annotation.Autowired;\n" + "import org.springframework.web.bind.annotation.*;\n" + "\n" + "@RestController\n" + "@RequestMapping(\"/" + StringUtil.camelCaseName(tableName) + "/\")\n" + "public class " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Controller extends CommonController<" + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Vo, " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + ", " + t + "> {" ); stringBuffer.append("\n"); stringBuffer.append("" + " @Autowired\n" + " private " + StringUtil.captureName(StringUtil.camelCaseName(tableName)) + "Service " + StringUtil.camelCaseName(tableName) + "Service;\n"); stringBuffer.append("}"); FileUtil.fileWriter(file, stringBuffer); }
需要注意的是：目前生成的pojo的主键，只用了@Id声明该属性为表主键，尚缺一个主键生成策略，这个需要根据自己的情况来选择主键生成策略
PS：缺少主键生成策略或者设置错误将会出现以下问题：
程序不报错，JPA查询出来的数据长度正常，内容都是重复的，但mysql数据库运行查询语句结果正常
/* JPA提供的四种主键生成策略 GenerationType.TABLE：使用一个特定的数据库表格来保存主键。 GenerationType.SEQUENCE：根据底层数据库的序列来生成主键，条件是数据库支持序列。 GenerationType.IDENTITY：主键由数据库自动生成（主要是自动增长型） GenerationType.AUTO：主键由程序控制。 */ @GeneratedValue(strategy = GenerationType.IDENTITY)
提供一个方法让外部直接调用
/** * 快速创建，供外部调用，调用之前先设置一下项目的基础路径 */ private String create() { List tableInfo = getTableInfo(); createPojo(tableInfo); createVo(tableInfo); createRepository(tableInfo); createService(tableInfo); createController(tableInfo); return tableName + " 后台代码生成完毕！"; }
main方法运行
public static void main(String[] args) { String[] tables = {"tb_user"}; for (int i = 0; i < tables.length; i++) { String msg = new CodeDOM(tables[i]).create(); System.out.println(msg); } }
我们查看一下生成的代码
package cn.huanzi.springbootjpa.tbuser.pojo;import lombok.Data;import javax.persistence.*;import java.io.Serializable;import java.util.Date;@Entity@Table(name = "tb_user")@Datapublic class TbUser implements Serializable { @Id @GeneratedValue(strategy= GenerationType.IDENTITY) private Integer id;//表id private String username;//用户名 private String password;//密码 private Date created;//创建时间 private Integer descriptionId;//关联详情id} package cn.huanzi.springbootjpa.tbuser.vo;import lombok.Data;import java.io.Serializable;import java.util.Date;@Datapublic class TbUserVo extends PageCondition implements Serializable { private Integer id;//表id private String username;//用户名 private String password;//密码 private Date created;//创建时间 private Integer descriptionId;//关联详情id}