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JSqlParser是一个与RDBMS无关的SQL语句解析器，支持多种方言，例如Oracle、SQL Server、MySQL、MariaDB、PostgreSQL、H2等。

JSqlParser将SQL语句转换为Java类的可遍历层次结构，还可以用于通过API从Java代码创建SQL语句。现在普遍使用的mybatis-plus以及分页插件PageHelper都是借助JSqlParser实现SQL解析的。

JSqlParser源码主要包括以下几类对象：

expression：SQL构建相关类，比如Function、EqualsTo、AndExpression、InExpression等表达式用于构建SQL。parser：SQL解析相关类，比如CCJSqlParserUtil、CCJSqlParserManager、抽象语法树对象等。schema：主要存放数据库schema相关的类 ，比如Database、Table、Column等。statement：封装了数据库操作对象，create、insert、delete、select、drop、alter、truncate等。util：各种工具类、不同DB版本、SQL标准等处理类，如SelectUtils、DatabaseType等。

解析SQL

对于下列SQL语句：

转换为Java对象层次结构为：

解析SQL代码实例：

public static void parseSQL() {    //Select语句样本    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语句样本    String sql2 = "insert into table(f1,f2) values (1,2)";    //Create语句样本    String sql3 = "CREATE TABLE `sys_user` (\n" +        "  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT "编号",\n" +        "  `name` varchar(200) DEFAULT "" COMMENT "名称",\n" +        "  `age` tinyint(4) DEFAULT NULL COMMENT "年龄",\n" +        "  `create_by` varchar(64) DEFAULT "" COMMENT "创建者",\n" +        "  `create_time` datetime DEFAULT NULL COMMENT "创建时间",\n" +        "  `update_by` varchar(64) DEFAULT "" COMMENT "更新者",\n" +        "  `update_time` datetime DEFAULT NULL COMMENT "更新时间",\n" +        "  `remark` varchar(500) DEFAULT NULL COMMENT "备注",\n" +        "  PRIMARY KEY (`id`)\n" +        ") ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT="用户表";";    try {        //处理Select语句        Select select = (Select) CCJSqlParserUtil.parse(sql1);        TablesNamesFinder tablesNamesFinder = new TablesNamesFinder();        List<String> tableList = tablesNamesFinder.getTableList(select);        // 获取到查询sql中的所有表名        System.out.println("表名:" + tableList);                   //处理Insert语句        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());                   //处理Create Table语句        Statement statement = CCJSqlParserUtil.parse(sql3);        if (statement instanceof CreateTable) {            CreateTable createTable = ((CreateTable) statement);            Table table = createTable.getTable();            //通过columnDefinition进而可以获取列名、数据类型等            List<ColumnDefinition> columnDefinitions = createTable.getColumnDefinitions();            System.out.println(table);            System.out.println(columnDefinitions);        }    } catch (Exception e) {        e.printStackTrace();    }}

输出如下：

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 "编号", `username` varchar (200) DEFAULT "" COMMENT "名称", `age` tinyint (4) DEFAULT NULL COMMENT "年龄", `create_by` varchar (64) DEFAULT "" COMMENT "创建者", `create_time` datetime DEFAULT NULL COMMENT "创建时间", `update_by` varchar (64) DEFAULT "" COMMENT "更新者", `update_time` datetime DEFAULT NULL COMMENT "更新时间", `remark` varchar (500) DEFAULT NULL COMMENT "备注"]

创建SQL

/** * 创建SQL查询语句 * * @throws JSQLParserException */public static void createSQL() throws JSQLParserException {  // 单表全量  Table table = new Table("sys_user");  //查询所有列  Select select = SelectUtils.buildSelectFromTable(table);  // SELECT * FROM sys_user  System.out.println(select);    // 指定列查询    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(); // 等于表达式    // 设置表达式左边值    equalsTo.setLeftExpression(new Column(table, "user_id"));     // 设置表达式右边值    equalsTo.setRightExpression(new StringValue("123456"));    // 转换为更细化的Select对象    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")); // 设置表达式左边值    notEqualsTo.setRightExpression(new StringValue("123456"));// 设置表达式右边值    PlainSelect plainSelectNot = (PlainSelect) select.getSelectBody();    plainSelectNot.setWhere(notEqualsTo);    System.out.println(plainSelectNot);//  SELECT * FROM sys_user WHERE sys_user.user_id <> "123456"    // 其他运算符, 参考上面代码添加表达式即可    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(); // 创建Like表达式对象    likeExpression.setLeftExpression(new Column("username")); // 表达式左边    likeExpression.setRightExpression(new StringValue("张%")); // 右边表达式    PlainSelect plainSelectLike = (PlainSelect) select.getSelectBody();    plainSelectLike.setWhere(likeExpression);    System.out.println(plainSelectLike); // SELECT * FROM sys_user WHERE username LIKE "张%"    // WHERE IN    Set<String> deptIds = Sets.newLinkedHashSet(); // 创建IN范围的元素集合    deptIds.add("0001");    deptIds.add("0002");    ItemsList itemsList = new ExpressionList(deptIds.stream().map(StringValue::new).collect(Collectors.toList())); // 把集合转变为JSQLParser需要的元素列表    InExpression inExpression = new InExpression(new Column("dept_id "), itemsList); // 创建IN表达式对象，传入列名及IN范围列表    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)); // 设置起点值    between.setBetweenExpressionEnd(new LongValue(30)); // 设置终点值    between.setLeftExpression(new Column("age")); // 设置左边的表达式，一般为列    PlainSelect plainSelectBetween = (PlainSelect) select.getSelectBody();    plainSelectBetween.setWhere(between);    System.out.println(plainSelectBetween); // SELECT * FROM sys_user WHERE age BETWEEN 18 AND 30    //  WHERE AND 多个条件结合,都需要成立    AndExpression andExpression = new AndExpression(); // AND 表达式    andExpression.setLeftExpression(equalsTo); // AND 左边表达式    andExpression.setRightExpression(between);  // AND 右边表达式    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 多个条件满足一个条件成立返回    OrExpression orExpression = new OrExpression();// OR 表达式    orExpression.setLeftExpression(equalsTo); // OR 左边表达式    orExpression.setRightExpression(between);  // OR 右边表达式    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(); // 创建排序对象    orderByElement.isAsc(); //  设置升序排列 从小到大    orderByElement.setExpression(new Column("col01")); // 设置排序字段    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); }

输出如下：

SELECT * FROM sys_userSELECT col1, col2 FROM sys_userSELECT * 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 "张%"SELECT * FROM sys_user WHERE dept_id  IN ("0001", "0002")SELECT * FROM sys_user WHERE age BETWEEN 18 AND 30SELECT * FROM sys_user WHERE sys_user.user_id = "123456" AND age BETWEEN 18 AND 30SELECT * FROM sys_user WHERE sys_user.user_id = "123456" OR age BETWEEN 18 AND 30SELECT * FROM sys_user WHERE sys_user.user_id = "123456" OR age BETWEEN 18 AND 30 ORDER BY col01