目录

• Maven 引用
• 远程仓库
• 依赖包
• SQL解析
• 获取SQL中的信息
• 创建Select的方式
• Insert 插入字段和值
• where条件中字段替换
• 解析SQL例子
• 校验SQL
• 总结

JSqlparser github地址

JSqlParser is a SQL statement parser. It translates SQLs in a traversable hierarchy of Java classes. JSqlParser is not limited to one database but provides support for a lot of specials of Oracle, SqlServer, MySQL, PostgreSQL … To name some, it has support for Oracles join syntax using (+), PostgreSQLs cast syntax using ::, relational operators like != and so on.

JSqlParser 是SQL语句分析的插件，他使用Java语言去解析SQL。

sqlparser提供很多的数据库语法解析支持其中支持很多oracle的特殊语法。

可以结合mybatis的拦截修改SQL来实现多租户、SQL拼接甚至联表的功能。

可以参考我之前写的MyBatis通过拦截修改SQL

Maven 引用

远程仓库

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<repositories>
     <repository>
         <id>jsqlparser-snapshots</id>
         <snapshots>
             <enabled>true</enabled>
         </snapshots>
         <url>https://oss.sonatype.org/content/groups/public/</url>
     </repository>
</repositories>

依赖包

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<dependency>
	<groupId>com.github.jsqlparser</groupId>
	<artifactId>jsqlparser</artifactId>
	<version>.4</version>
</dependency>

SQL解析

获取SQL中的信息

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public class TestSqlparser {
 
    public static void main(String[] args) throws JSQLParserException {
        // 根据sql创建select
        Select stmt = (Select) CCJSqlParserUtil.parse("SELECT col AS a, col2 AS b, col3 AS c FROM table T WHERE col1 = 10 AND col2 = 20 AND col3 = 30");
 
        Map<String, Expression> map = new HashMap<>();
        Map<String, String> mapTable = new HashMap<>();
 
        ((PlainSelect) stmt.getSelectBody()).getFromItem().accept(new FromItemVisitorAdapter() {
            @Override
            public void visit(Table table) {
                // 获取别名 => 表名
                mapTable.put(table.getAlias().getName(), table.getName());
            }
        });
 
        ((PlainSelect) stmt.getSelectBody()).getWhere().accept(new ExpressionVisitorAdapter() {
            @Override
            public void visit(AndExpression expr) {
                // 获取where表达式
                System.out.println(expr);
            }
        });
 
        for (SelectItem selectItem : ((PlainSelect)stmt.getSelectBody()).getSelectItems()) {
            selectItem.accept(new SelectItemVisitorAdapter() {
                @Override
                public void visit(SelectExpressionItem item) {
                    // 获取字段别名 => 字段名
                    map.put(item.getAlias().getName(), item.getExpression());
                }
            });
        }
 
        System.out.println("map " + map);
        System.out.println("mapTables" + mapTable);
    }
}

创建Select的方式

创建Select（非SQL String 创建）

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@Test
public void testCreateSelect () throws JSQLParserException {
     Select select = SelectUtils.buildSelectFromTable(new Table("mytable"));
     Select select = SelectUtils.buildSelectFromTableAndExpressions(new Table("mytable"), new Column("a"), new Column("b"));
     Select select = SelectUtils.buildSelectFromTableAndExpressions(new Table("mytable"), "a+b", "test");
 
     System.out.println(select.toString());
     System.out.println(select.toString());
     System.out.println(select.toString());
 }

Insert 插入字段和值

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@Test
public void testCreateSelect() throws JSQLParserException {
    Insert insert = (Insert) CCJSqlParserUtil.parse("insert into mytable (col) values (1)");
    System.out.println(insert.toString());
 
    //adding a column
    insert.getColumns().add(new Column("col"));
 
    //adding a value using a visitor
    insert.getItemsList().accept(new ItemsListVisitor() {
 
        public void visit(SubSelect subSelect) {
            throw new UnsupportedOperationException("Not supported yet.");
        }
 
        public void visit(ExpressionList expressionList) {
            expressionList.getExpressions().add(new LongValue());
        }
 
        @Override
        public void visit(NamedExpressionList namedExpressionList) {
 
        }
 
        public void visit(MultiExpressionList multiExprList) {
            throw new UnsupportedOperationException("Not supported yet.");
        }
    });
    System.out.println(insert.toString());
 
    //adding another column
    insert.getColumns().add(new Column("col"));
 
    //adding another value (the easy way)
    ((ExpressionList) insert.getItemsList()).getExpressions().add(new LongValue());
 
    System.out.println(insert.toString());
}

复制
import net.sf.jsqlparser.JSQLParserException;
import net.sf.jsqlparser.expression.LongValue;
import net.sf.jsqlparser.expression.StringValue;
import net.sf.jsqlparser.parser.CCJSqlParserUtil;
import net.sf.jsqlparser.statement.Statement;
import net.sf.jsqlparser.util.deparser.ExpressionDeParser;
import net.sf.jsqlparser.util.deparser.SelectDeParser;
import net.sf.jsqlparser.util.deparser.StatementDeParser;
 
public class ReplaceColumnValues {
 
    static class ReplaceColumnAndLongValues extends ExpressionDeParser {
 
        @Override
        public void visit(StringValue stringValue) {
            this.getBuffer().append("?");
        }
 
        @Override
        public void visit(LongValue longValue) {
            this.getBuffer().append("?");
        }
    }
 
    public static String cleanStatement(String sql) throws JSQLParserException {
        StringBuilder buffer = new StringBuilder();
        ExpressionDeParser expr = new ReplaceColumnAndLongValues();
 
        SelectDeParser selectDeparser = new SelectDeParser(expr, buffer);
        expr.setSelectVisitor(selectDeparser);
        expr.setBuffer(buffer);
        StatementDeParser stmtDeparser = new StatementDeParser(expr, selectDeparser, buffer);
 
        Statement stmt = CCJSqlParserUtil.parse(sql);
 
        stmt.accept(stmtDeparser);
        return stmtDeparser.getBuffer().toString();
    }
 
    public static void main(String[] args) throws JSQLParserException {
        System.out.println(cleanStatement("SELECT 'abc', FROM mytable WHERE col='test'"));
        System.out.println(cleanStatement("UPDATE table A SET A.columna = 'XXX' WHERE A.cod_table = 'YYY'"));
        System.out.println(cleanStatement("INSERT INTO example (num, name, address, tel) VALUES (, 'name', 'test ', '1234-1234')"));
        System.out.println(cleanStatement("DELETE FROM table where col=5 and col2=4"));
    }
}

输出：

SELECT ?, ? FROM mytable WHERE col = ?

UPDATE table1 A SET A.columna = ? WHERE A.cod_table = ?

INSERT INTO example (num, name, address, tel) VALUES (?, ?, ?, ?)

DELETE FROM table1 WHERE col = ? AND col2 = ?

where条件中字段替换

替换条件字段col_1到col1

复制
@Test
 public void replace () throws JSQLParserException {
     Select stmt = (Select) CCJSqlParserUtil.parse("SELECT col AS a, col2 AS b, col3 AS c FROM table WHERE col_1 = 10 AND col_2 = 20 AND col_3 = 30");
     System.out.println("before " + stmt.toString());
 
     ((PlainSelect)stmt.getSelectBody()).getWhere().accept(new ExpressionVisitorAdapter() {
         @Override
         public void visit(Column column) {
             column.setColumnName(column.getColumnName().replace("_", ""));
         }
     });
 
     System.out.println("after " + stmt.toString());
 }

解析SQL例子

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Statement stmt = CCJSqlParserUtil.parse("SELECT * FROM tab");
Statements stmt = CCJSqlParserUtil.parseStatements("SELECT * FROM tab; SELECT * FROM tab2");
Expression expr = CCJSqlParserUtil.parseExpression("a*(+mycolumn)");

可以直接将String SQL片段解析成Expression再将expr插入到SQL语句中。

获取所有tableNames

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Statement statement = CCJSqlParserUtil.parse("SELECT * FROM MY_TABLE");
Select selectStatement = (Select) statement;
TablesNamesFinder tablesNamesFinder = new TablesNamesFinder();
List<String> tableList = tablesNamesFinder.getTableList(selectStatement);

自动生成别名

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Select select = (Select) CCJSqlParserUtil.parse("select a,b,c from test");
final AddAliasesVisitor instance = new AddAliasesVisitor();
select.getSelectBody().accept(instance);

结果：

SELECT a AS A1, b AS A2, c AS A3 FROM test

SQL函数

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/**
 * SQL 函数
 * SELECT function(列) FROM 表
 */
@Test
public void testFun() throws JSQLParserException {
    Table t = new Table("tab1").withAlias(new Alias("t1").withUseAs(true)); // 表1
    PlainSelect plainSelect = new PlainSelect();
    plainSelect.setFromItem(t); // 设置FROM t1= >  SELECT  FROM tab1 AS t1
    List<SelectItem> selectItemList = new ArrayList<>(); // 查询元素集合
    SelectExpressionItem selectExpressionItem = new SelectExpressionItem(); // 元素1表达式
    selectExpressionItem.setExpression(new Column(t1,"col001"));
    SelectExpressionItem selectExpressionItem = new SelectExpressionItem(); // 元素2表达式
    selectExpressionItem.setExpression(new Column(t1,"col002"));
    selectItemList.add(, selectExpressionItem001); // 添加入队
    selectItemList.add(, selectExpressionItem002); // 添加入队
 
    // COUNT
    SelectExpressionItem selectExpressionItemCount = new SelectExpressionItem(); // 创建函数元素表达式
    selectExpressionItemCount.setAlias(new Alias("count")); // 设置别名
    Function function = new Function(); // 创建函数对象  Function extends ASTNodeAccessImpl implements Expression
    function.setName("COUNT"); // 设置函数名
    ExpressionList expressionListCount = new ExpressionList(); // 创建参数表达式
    expressionListCount.setExpressions(Collections.singletonList(new Column(t, "id")));
    function.setParameters(expressionListCount); // 设置参数
    selectExpressionItemCount.setExpression(function);
    selectItemList.add(,selectExpressionItemCount);
 
    plainSelect.setSelectItems(selectItemList); // 添加查询元素集合入select对象
    System.err.println(plainSelect); // SELECT t.col001, t1.col002, COUNT(t1.id) AS count FROM tab1 AS t1
}

单表where条件拼装

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/**
 * 单表SQL查询
 *
 * @throws JSQLParserException
 */
@Test
public void testSelectOneTable() throws JSQLParserException {
    // 单表全量
    Table table = new Table("test");
    Select select = SelectUtils.buildSelectFromTable(table);
    System.err.println(select); // SELECT * FROM test
 
    // 指定列查询
    Select buildSelectFromTableAndExpressions = SelectUtils.buildSelectFromTableAndExpressions(new Table("test"), new Column("col"), new Column("col2"));
    System.err.println(buildSelectFromTableAndExpressions); // SELECT col, col2 FROM test
 
    // WHERE =
    EqualsTo equalsTo = new EqualsTo(); // 等于表达式
    equalsTo.setLeftExpression(new Column(table, "user_id")); // 设置表达式左边值
    equalsTo.setRightExpression(new StringValue(""));// 设置表达式右边值
    PlainSelect plainSelect = (PlainSelect) select.getSelectBody(); // 转换为更细化的Select对象
    plainSelect.setWhere(equalsTo);
    System.err.println(plainSelect);//  SELECT * FROM test WHERE test.user_id = ''
 
    // WHERE  != <>
    NotEqualsTo notEqualsTo = new NotEqualsTo();
    notEqualsTo.setLeftExpression(new Column(table, "user_id")); // 设置表达式左边值
    notEqualsTo.setRightExpression(new StringValue(""));// 设置表达式右边值
    PlainSelect plainSelectNot = (PlainSelect) select.getSelectBody();
    plainSelectNot.setWhere(notEqualsTo);
    System.err.println(plainSelectNot);//  SELECT * FROM test WHERE test.user_id <> ''
 
    // 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.err.println(plainSelectLike); // SELECT * FROM test WHERE username LIKE '张%'
 
    // WHERE IN
    Set<String> deptIds = Sets.newLinkedHashSet(); // 创建IN范围的元素集合
    deptIds.add("");
    deptIds.add("");
    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.err.println(plainSelectIn); // SELECT * FROM test WHERE dept_id  IN ('', '0002')
 
    // WHERE BETWEEN AND
    Between between = new Between();
    between.setBetweenExpressionStart(new LongValue()); // 设置起点值
    between.setBetweenExpressionEnd(new LongValue()); // 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.err.println(plainSelectBetween); // SELECT * FROM test WHERE age BETWEEN 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.err.println(plainSelectAnd); //  SELECT * FROM test WHERE test.user_id = '' 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.err.println(plainSelectOr); // SELECT * FROM test WHERE test.user_id = '' 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("col")); // 设置排序字段
    PlainSelect plainSelectOrderBy = (PlainSelect) select.getSelectBody();
    plainSelectOrderBy.addOrderByElements(orderByElement);
    System.err.println(plainSelectOrderBy); // SELECT * FROM test WHERE test.user_id = '' OR age BETWEEN 18 AND 30 ORDER BY col01
}

JOIN 拼装

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/**
  * 多表SQL查询
  * JOIN / INNER JOIN: 如果表中有至少一个匹配，则返回行
  * LEFT JOIN: 即使右表中没有匹配，也从左表返回所有的行
  * RIGHT JOIN: 即使左表中没有匹配，也从右表返回所有的行
  * FULL JOIN: 只要其中一个表中存在匹配，就返回行
  */
 @Test
 public void testSelectManyTable() {
     Table t = new Table("tab1").withAlias(new Alias("t1").withUseAs(true)); // 表1
     Table t = new Table("tab2").withAlias(new Alias("t2", false)); // 表2
     PlainSelect plainSelect = new PlainSelect().addSelectItems(new AllColumns()).withFromItem(t); // SELECT * FROM tab1 AS t1
 
     // JOIN ON 如果表中有至少一个匹配，则返回行
     Join join = new Join(); // 创建Join对象
     join.withRightItem(t); // 添加Join的表 JOIN t2 =>JOIN tab2 t2
     EqualsTo equalsTo = new EqualsTo(); // 添加 = 条件表达式  t.user_id  = t2.user_id
     equalsTo.setLeftExpression(new Column(t, "user_id "));
     equalsTo.setRightExpression(new Column(t, "user_id "));
     join.withOnExpression(equalsTo);// 添加ON
     plainSelect.addJoins(join);
     System.err.println(plainSelect); // SELECT * FROM tab AS t1 JOIN tab2 t2 ON t1.user_id  = t2.user_id
 
     // 设置join参数可实现其他类型join
     // join.setLeft(true); LEFT JOIN
     // join.setRight(true);  RIGHT JOIN
     // join.setFull(true); FULL JOIN
     // join.setInner(true);
}

校验SQL

复制
String sql = "DROP INDEX IF EXISTS idx_tab_id;";
 
// validate statement if it's valid for all given databases.
Validation validation = new Validation(Arrays.asList(DatabaseType.SQLSERVER, DatabaseType.MARIADB,
                DatabaseType.POSTGRESQL, DatabaseType.H), sql);
List<ValidationError> errors = validation.validate();
 
// validate against pre-defined FeaturesAllowed.DML set
String sql = "CREATE TABLE tab (id NUMERIC(10), val VARCHAR(30))";
Validation validation = new Validation(Arrays.asList(FeaturesAllowed.DML), sql);
List<ValidationError> errors = validation.validate();
// only DML is allowed, got error for using a DDL statement
log.error (errors);

Validates metadata such as names of tables, views, columns for their existence or non-existence

复制
java.sql.Connection connection = ...;
String sql = "ALTER TABLE mytable ADD price numeric(,5) not null";
Validation validation = new Validation(Arrays.asList(new JdbcDatabaseMetaDataCapability(connection, 	
// NamesLookup: Databases handle names differently
        NamesLookup.UPPERCASE)), sql);
List<ValidationError> errors = validation.validate();
 
// do something else with the parsed statements
Statements statements = validation.getParsedStatements();
 
// check for validation-errors
if (!errors.isEmpty()) {
    ...
}

总结

我们可以借助JSqlparser来解析SQL并且动态拼接生成SQL，在Mybatis-plus中的租户其实也是类似这样实现的。

甚至有兴趣的同学可以自己做一个SQL拼装器，将前台筛选的条件转换为SQL进行查询。所有的查询字段、条件、联表等等都做成动态拼装。