利用JDBC根据表结构生成ModelClass

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有时为了加快开发效率，特别是项目初始阶段，数据库设计完成之后，希望直接读取表结构以生成数据库实体。本例中为生成hibernate实体:

//根据数据库生成实体模型的工具类public class ModelClassBuilder {    // mysql链接相关    private final String driverClassName = "com.mysql.jdbc.Driver";    private final String url = "jdbc:mysql:localhost/test?useUnicode=true&amp;autoReconnect=true";    private final String username = "test";    private final String password = "test";    private final String tableName;    private final String tableClassName;    public ModelClassBuilder(String tableName, String tableClassName) {        this.tableName = tableName;        this.tableClassName = tableClassName;    }    private Connection getDbConnection() {        try {            Class.forName(driverClassName);            Class.forName(driverClassName).newInstance();            StringBuilder connectUrlSb = new StringBuilder(url);            connectUrlSb.append("&user=").append(username);            connectUrlSb.append("&password=").append(password);            Connection con = DriverManager.getConnection(connectUrlSb.toString());            return con;        } catch (Exception e) {            e.printStackTrace();            return null;        }    }    private ResultSet readColumsFromJdbc(Connection connection) {        try {            String queryColumsSql = "select * from information_schema.columns where table_name = '" + tableName + "'";            Statement stmt = connection.createStatement();            return stmt.executeQuery(queryColumsSql);        } catch (Exception e) {            e.printStackTrace();            return null;        }    }    private List<ColnumEntity> getColunFromRs(ResultSet rs) throws Exception {        ResultSetMetaData metaData = rs.getMetaData();        int columns = metaData.getColumnCount();        for (int index = 1; index <= columns; index++) {            // System.out.print(metaData.getColumnName(index));            // System.out.print("\t\t");        }        System.out.println();        List<ColnumEntity> results = new ArrayList<ColnumEntity>();        while (rs.next()) {            // for (int i = 1; i <= columns; i++){            // System.out.print(resultSet.getString(i));            // System.out.print("\t\t");            // }            // System.out.println();            String columnKey = rs.getString("COLUMN_KEY");// 包含pri则为主键            String columnName = rs.getString("COLUMN_NAME");            boolean isNullAble = rs.getBoolean("IS_NULLABLE");            String dataType = rs.getString("DATA_TYPE");            String maxLength = rs.getString("CHARACTER_MAXIMUM_LENGTH");            String comment = rs.getString("COLUMN_COMMENT");            results.add(new ColnumEntity(columnKey, columnName, isNullAble, dataType, maxLength, comment));        }        return results;    }    //注解加在field上    public void genModelClass() {        try {            Connection con = getDbConnection();            ResultSet resultSet = readColumsFromJdbc(con);            List<ColnumEntity> colnumEntities = getColunFromRs(resultSet);            StringBuilder sb = new StringBuilder();            sb.append("import java.io.Serializable;");            sb.append("import java.util.Date;");            sb.append("import javax.persistence.Column;");            sb.append("import javax.persistence.Entity;");            sb.append("import javax.persistence.Id;");            sb.append("import javax.persistence.Table;");            sb.append("import javax.validation.constraints.NotNull;");            sb.append("import org.hibernate.validator.constraints.NotBlank;");            sb.append("import cn.com.maitao.common.model.BaseObject;");            sb.append("@Entity").append("\n");            sb.append(String.format("@Table(name = \"%s\")", tableName));            sb.append("@SuppressWarnings(\"serial\")");            sb.append("public class ").append(tableClassName).append(" extends BaseObject implements Serializable").append("{")                    .append("\n");            //field            for (ColnumEntity colnumEntity : colnumEntities) {                String columnName = colnumEntity.columnName;                String fieldName = genFieldName(columnName);                String dataType = getDataType(colnumEntity);                sb.append("\t//").append(colnumEntity.comment).append("\n");                // field                if (colnumEntity.columnKey.equalsIgnoreCase("pri")) {                    sb.append("@Id").append("\n");                }                if (!colnumEntity.isNullAble) {                    if (dataType.equals("String")) {                        sb.append(String.format("@NotBlank(message = \"%s不能为空\")", fieldName)).append("\n");                    } else {                        sb.append(String.format("@NotNull(message = \"%s不能为空\")", fieldName)).append("\n");                    }                }                sb.append(String.format("@Column(name = \"%s\")", columnName));                sb.append(String.format(field_Pattern, dataType, fieldName)).append("\n\n");            }            for (ColnumEntity colnumEntity : colnumEntities) {                String columnName = colnumEntity.columnName;                String fieldName = genFieldName(columnName);                String dataType = getDataType(colnumEntity);                //sb.append("\t//").append(colnumEntity.comment).append("\n");                // set                sb.append(String.format(method_Set_Pattern, firstToUpperCase(fieldName), dataType, fieldName, fieldName, fieldName))                        .append("\n");                // get                sb.append(String.format(method_Get_Pattern, dataType, firstToUpperCase(fieldName), fieldName)).append("\n");            }            sb.append("}");            System.out.println(sb.toString());        } catch (Exception e) {            e.printStackTrace();        }    }    private String field_Pattern = "private %s %s;";    private String method_Get_Pattern = "public %s get%s(){return this.%s;} ";    private String method_Set_Pattern = "public void set%s(%s %s){this.%s = %s;} ";    private String getDataType(ColnumEntity colnumEntity) {        String type = colnumEntity.dataType.toLowerCase();        if (type.equalsIgnoreCase("datetime") || type.equalsIgnoreCase("date") || type.equalsIgnoreCase("time")                || type.equalsIgnoreCase("timestamp")) {            return "Date";        }        if (type.equalsIgnoreCase("bigint")) {            return "Long";        } else if (type.contains("int")) {            return "Integer";        }        if (type.equalsIgnoreCase("float")) {            return "Float";        }        if (type.equalsIgnoreCase("double") || type.equalsIgnoreCase("decimal")) {            return "Double";        }        return "String";    }    class ColnumEntity {        String columnKey;        String columnName;        boolean isNullAble;        String dataType;        String maxLength;        String comment;        public ColnumEntity(String columnKey, String columnName, boolean isNullAble, String dataType, String maxLength, String comment) {            super();            this.columnKey = columnKey;            this.columnName = columnName;            this.isNullAble = isNullAble;            this.dataType = dataType;            this.maxLength = maxLength;            this.comment = comment;        }    }    private static final Pattern pattern = Pattern.compile("_(\\w)");    public static String genFieldName(String columnName) {        Matcher matcher = pattern.matcher(columnName);        while (matcher.find()) {            columnName = columnName.replaceFirst(matcher.group(0), matcher.group(1).toUpperCase());        }        columnName.replaceAll("_", "");        return columnName;    }    // 将首字母改成大写    private String firstToUpperCase(String str) {        if (StringUtils.isBlank(str)) {            return "";        }        if (str.length() == 1) {            return str.toUpperCase();        }        StringBuilder sb = new StringBuilder();        sb.append(str.substring(0, 1).toUpperCase());        sb.append(str.substring(1, str.length()));        return sb.toString();    }    public static void main(String[] args) {        ModelClassBuilder builder = new ModelClassBuilder("notice_wx_template", "NoticeWxTemplateModel");        builder.genModelClass();    }}