JSqlParser是一個與RDBMS無關的SQL語句解析器，支持多種方言，例如Oracle、SQL Server、MySQL、MariaDB、PostgreSQL、H2等。

JSqlParser將SQL語句轉換為JAVA類的可遍歷層次結構，還可以用于通過API從Java代碼創建SQL語句。現在普遍使用的MyBatis-plus以及分頁插件PageHelper都是借助JSqlParser實現SQL解析的。

JSqlParser源碼主要包括以下幾類對象：

• expression：SQL構建相關類，比如Function、EqualsTo、AndExpression、InExpression等表達式用于構建SQL。
• parser：SQL解析相關類，比如CCJSqlParserUtil、CCJSqlParserManager、抽象語法樹對象等。
• schema：主要存放數據庫schema相關的類 ，比如Database、Table、Column等。
• statement：封裝了數據庫操作對象，create、insert、delete、select、drop、alter、truncate等。
• util：各種工具類、不同DB版本、SQL標準等處理類，如SelectUtils、DatabaseType等。

解析SQL

對于下列SQL語句：

SELECT name, age, score FROM user WHERE id=1;

轉換為Java對象層次結構為：

解析SQL代碼實例：

public static void parseSQL() {
    //Select語句樣本
    String sql1 = "select t1.f1,t1.f2,t2.id,count(*) from table1 t1 left join table2 t2 right join (select * from table3) t3 where t1.id='10' or (t1.id between 1 and 3 and t1.id>'12') group by t.f1 order by t.f1 desc,tf2 asc limit 1,20";
    //Insert語句樣本
    String sql2 = "insert into table(f1,f2) values (1,2)";
    //Create語句樣本
    String sql3 = "CREATE TABLE `sys_user` (n" +
        "  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '編號',n" +
        "  `name` varchar(200) DEFAULT '' COMMENT '名稱',n" +
        "  `age` tinyint(4) DEFAULT NULL COMMENT '年齡',n" +
        "  `create_by` varchar(64) DEFAULT '' COMMENT '創建者',n" +
        "  `create_time` datetime DEFAULT NULL COMMENT '創建時間',n" +
        "  `update_by` varchar(64) DEFAULT '' COMMENT '更新者',n" +
        "  `update_time` datetime DEFAULT NULL COMMENT '更新時間',n" +
        "  `remark` varchar(500) DEFAULT NULL COMMENT '備注',n" +
        "  PRIMARY KEY (`id`)n" +
        ") ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='用戶表';";
    try {
        //處理Select語句
        Select select = (Select) CCJSqlParserUtil.parse(sql1);
        TablesNamesFinder tablesNamesFinder = new TablesNamesFinder();
        List<String> tableList = tablesNamesFinder.getTableList(select);
        // 獲取到查詢sql中的所有表名
        System.out.println("表名:" + tableList);
           
        //處理Insert語句
        Insert insert = (Insert) CCJSqlParserUtil.parse(sql2);
        System.out.println("插入的表" + insert.getTable());
        System.out.println("插入的列" + insert.getColumns());
        System.out.println("插入的值" + insert.getItemsList());
           
        //處理Create Table語句
        Statement statement = CCJSqlParserUtil.parse(sql3);
        if (statement instanceof CreateTable) {
            CreateTable createTable = ((CreateTable) statement);
            Table table = createTable.getTable();
            //通過columnDefinition進而可以獲取列名、數據類型等
            List<ColumnDefinition> columnDefinitions = createTable.getColumnDefinitions();
            System.out.println(table);
            System.out.println(columnDefinitions);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

輸出如下：

表名:[table1, table2, table3]
插入的表table
插入的列[f1, f2]
插入的值(1, 2)
`sys_user`
[`id` bigint (20) NOT NULL AUTO_INCREMENT COMMENT '編號', `username` varchar (200) DEFAULT '' COMMENT '名稱', `age` tinyint (4) DEFAULT NULL COMMENT '年齡', `create_by` varchar (64) DEFAULT '' COMMENT '創建者', `create_time` datetime DEFAULT NULL COMMENT '創建時間', `update_by` varchar (64) DEFAULT '' COMMENT '更新者', `update_time` datetime DEFAULT NULL COMMENT '更新時間', `remark` varchar (500) DEFAULT NULL COMMENT '備注']

創建SQL

/**
 * 創建SQL查詢語句
 *
 * @throws JSQLParserException
 */
public static void createSQL() throws JSQLParserException {
  // 單表全量
  Table table = new Table("sys_user");
  //查詢所有列
  Select select = SelectUtils.buildSelectFromTable(table);
  // SELECT * FROM sys_user
  System.out.println(select);

    // 指定列查詢
    Select buildSelectFromTableAndExpressions = SelectUtils.buildSelectFromTableAndExpressions(new Table("test"), new Column("col1"), new Column("col2"));
    // SELECT col1, col2 FROM sys_user
    System.out.println(buildSelectFromTableAndExpressions);

    // WHERE =
    EqualsTo equalsTo = new EqualsTo(); // 等于表達式
    // 設置表達式左邊值
    equalsTo.setLeftExpression(new Column(table, "user_id")); 
    // 設置表達式右邊值
    equalsTo.setRightExpression(new StringValue("123456"));
    // 轉換為更細化的Select對象
    PlainSelect plainSelect = (PlainSelect) select.getSelectBody();
    plainSelect.setWhere(equalsTo);
    // SELECT * FROM sys_user WHERE sys_user.user_id = '123456'
    System.out.println(plainSelect);

    // WHERE  != <>
    NotEqualsTo notEqualsTo = new NotEqualsTo();
    notEqualsTo.setLeftExpression(new Column(table, "user_id")); // 設置表達式左邊值
    notEqualsTo.setRightExpression(new StringValue("123456"));// 設置表達式右邊值
    PlainSelect plainSelectNot = (PlainSelect) select.getSelectBody();
    plainSelectNot.setWhere(notEqualsTo);
    System.out.println(plainSelectNot);//  SELECT * FROM sys_user WHERE sys_user.user_id <> '123456'

    // 其他運算符, 參考上面代碼添加表達式即可
    GreaterThan gt = new GreaterThan(); // ">"
    GreaterThanEquals geq = new GreaterThanEquals(); // ">="
    MinorThan mt = new MinorThan(); // "<"
    MinorThanEquals leq = new MinorThanEquals();// "<="
    IsNullExpression isNull = new IsNullExpression(); // "is null"
    isNull.setNot(true);// "is not null"
    LikeExpression nlike = new LikeExpression();
    nlike.setNot(true); // "not like"
    Between bt = new Between();
    bt.setNot(true);// "not between"

    // WHERE LIKE
    LikeExpression likeExpression = new LikeExpression(); // 創建Like表達式對象
    likeExpression.setLeftExpression(new Column("username")); // 表達式左邊
    likeExpression.setRightExpression(new StringValue("張%")); // 右邊表達式
    PlainSelect plainSelectLike = (PlainSelect) select.getSelectBody();
    plainSelectLike.setWhere(likeExpression);
    System.out.println(plainSelectLike); // SELECT * FROM sys_user WHERE username LIKE '張%'

    // WHERE IN
    Set<String> deptIds = Sets.newLinkedHashSet(); // 創建IN范圍的元素集合
    deptIds.add("0001");
    deptIds.add("0002");
    ItemsList itemsList = new ExpressionList(deptIds.stream().map(StringValue::new).collect(Collectors.toList())); // 把集合轉變為JSQLParser需要的元素列表
    InExpression inExpression = new InExpression(new Column("dept_id "), itemsList); // 創建IN表達式對象，傳入列名及IN范圍列表
    PlainSelect plainSelectIn = (PlainSelect) select.getSelectBody();
    plainSelectIn.setWhere(inExpression);
    System.out.println(plainSelectIn); // SELECT * FROM sys_user WHERE dept_id  IN ('0001', '0002')

    // WHERE BETWEEN AND
    Between between = new Between();
    between.setBetweenExpressionStart(new LongValue(18)); // 設置起點值
    between.setBetweenExpressionEnd(new LongValue(30)); // 設置終點值
    between.setLeftExpression(new Column("age")); // 設置左邊的表達式，一般為列
    PlainSelect plainSelectBetween = (PlainSelect) select.getSelectBody();
    plainSelectBetween.setWhere(between);
    System.out.println(plainSelectBetween); // SELECT * FROM sys_user WHERE age BETWEEN 18 AND 30

    //  WHERE AND 多個條件結合,都需要成立
    AndExpression andExpression = new AndExpression(); // AND 表達式
    andExpression.setLeftExpression(equalsTo); // AND 左邊表達式
    andExpression.setRightExpression(between);  // AND 右邊表達式
    PlainSelect plainSelectAnd = (PlainSelect) select.getSelectBody();
    plainSelectAnd.setWhere(andExpression);
    System.out.println(plainSelectAnd); //  SELECT * FROM sys_user WHERE sys_user.user_id = '123456' AND age BETWEEN 18 AND 30

    //  WHERE OR 多個條件滿足一個條件成立返回
    OrExpression orExpression = new OrExpression();// OR 表達式
    orExpression.setLeftExpression(equalsTo); // OR 左邊表達式
    orExpression.setRightExpression(between);  // OR 右邊表達式
    PlainSelect plainSelectOr = (PlainSelect) select.getSelectBody();
    plainSelectOr.setWhere(orExpression);
    System.out.println(plainSelectOr); // SELECT * FROM sys_user WHERE sys_user.user_id = '123456' OR age BETWEEN 18 AND 30

    // ORDER BY 排序
    OrderByElement orderByElement = new OrderByElement(); // 創建排序對象
    orderByElement.isAsc(); //  設置升序排列 從小到大
    orderByElement.setExpression(new Column("col01")); // 設置排序字段
    PlainSelect plainSelectOrderBy = (PlainSelect) select.getSelectBody();
    plainSelectOrderBy.addOrderByElements(orderByElement);
    // SELECT * FROM sys_user WHERE sys_user.user_id = '123456' OR age BETWEEN 18 AND 30 ORDER BY col01
    System.out.println(plainSelectOrderBy); 
}

輸出如下：

SELECT * FROM sys_user
SELECT col1, col2 FROM sys_user
SELECT * FROM sys_user WHERE sys_user.user_id = '123456'
SELECT * FROM sys_user WHERE sys_user.user_id <> '123456'
SELECT * FROM sys_user WHERE username LIKE '張%'
SELECT * FROM sys_user WHERE dept_id  IN ('0001', '0002')
SELECT * FROM sys_user WHERE age BETWEEN 18 AND 30
SELECT * FROM sys_user WHERE sys_user.user_id = '123456' AND age BETWEEN 18 AND 30
SELECT * FROM sys_user WHERE sys_user.user_id = '123456' OR age BETWEEN 18 AND 30
SELECT * FROM sys_user WHERE sys_user.user_id = '123456' OR age BETWEEN 18 AND 30 ORDER BY col01